diff --git a/site/e2e/film.spec.ts b/site/e2e/film.spec.ts
new file mode 100644
index 0000000..4d80c07
--- /dev/null
+++ b/site/e2e/film.spec.ts
@@ -0,0 +1,65 @@
+import { expect, test, type Page } from "@playwright/test";
+
+const PAGE = "/";
+
+/** Scrolls to the film and mutes it for autoplay. */
+async function reach(page: Page): Promise<string[]> {
+  const errors: string[] = [];
+  page.on("pageerror", (e) => errors.push(String(e)));
+  page.on("console", (m) => {
+    if (m.type() === "error") errors.push(m.text());
+  });
+  await page.goto(PAGE);
+  await page.locator("#film").scrollIntoViewIfNeeded();
+  await expect(page.locator("#film")).toHaveClass(/seen/);
+  await page.evaluate(() => {
+    const video = document.querySelector<HTMLVideoElement>("#film video")!;
+    video.muted = true;
+    Object.assign(window, { filmVideo: video });
+  });
+  return errors;
+}
+
+const box = (page: Page) => page.locator("#film video").evaluate((v) => v.getBoundingClientRect().toJSON());
+
+test("the film flattens to play and returns to its face", async ({ page }) => {
+  const errors = await reach(page);
+  await expect(page.locator("#film video")).toHaveAttribute("preload", "metadata");
+  const face = await box(page);
+  const play = page.getByRole("button", { name: "Play the film" });
+  await play.click();
+  await expect.poll(() => page.locator("#film video").evaluate((v: HTMLVideoElement) => v.paused)).toBe(false);
+  await expect.poll(() => page.locator("#film video").evaluate((v) => v.getAnimations().length)).toBe(0);
+  const flat = await box(page);
+  expect(flat.width / flat.height).toBeCloseTo(16 / 9, 1);
+  expect(flat.width).toBeGreaterThan(page.viewportSize()!.width * 0.7);
+  expect(flat.width).toBeGreaterThan(face.width * 1.5);
+  await expect(page.locator("#film video")).toHaveJSProperty("controls", true);
+
+  await page.keyboard.press("Escape");
+  await expect(play).toBeFocused();
+  await expect.poll(() => page.locator("#film video").evaluate((v) => v.getAnimations().length)).toBe(0);
+  const back = await box(page);
+  expect(back.width).toBeCloseTo(face.width, 0);
+  expect(back.height).toBeCloseTo(face.height, 0);
+  const state = await page.evaluate(() => {
+    const video = document.querySelector<HTMLVideoElement>("#film video")!;
+    return { same: video === (window as unknown as { filmVideo: HTMLVideoElement }).filmVideo, paused: video.paused, at: video.currentTime };
+  });
+  expect(state.same).toBe(true);
+  expect(state.paused).toBe(true);
+  expect(state.at).toBeGreaterThan(0);
+  expect(errors).toEqual([]);
+});
+
+test("with reduced motion the film plays flat at once", async ({ page }) => {
+  await page.emulateMedia({ reducedMotion: "reduce" });
+  const errors = await reach(page);
+  await page.getByRole("button", { name: "Play the film" }).click();
+  const video = page.locator("#film video");
+  expect(await video.evaluate((v) => [v.getAnimations().length, getComputedStyle(v).transform])).toEqual([0, "none"]);
+  await expect.poll(() => video.evaluate((v: HTMLVideoElement) => v.paused)).toBe(false);
+  await page.keyboard.press("Escape");
+  await expect(page.getByRole("button", { name: "Play the film" })).toBeFocused();
+  expect(errors).toEqual([]);
+});
diff --git a/site/e2e/night.spec.ts b/site/e2e/night.spec.ts
new file mode 100644
index 0000000..0a2fb13
--- /dev/null
+++ b/site/e2e/night.spec.ts
@@ -0,0 +1,111 @@
+import { expect, test, type Page } from "@playwright/test";
+
+const PAGE = "/";
+const DESK = { light: "rgb(230, 230, 226)", dark: "rgb(58, 58, 58)" };
+
+let errors: string[] = [];
+
+test.beforeEach(async ({ page }) => {
+  errors = [];
+  page.on("pageerror", (e) => errors.push(String(e)));
+});
+
+test.afterEach(() => expect(errors).toEqual([]));
+
+const open = async (page: Page) => {
+  await page.goto(PAGE);
+  await expect(page.locator(".model .block").first()).toBeAttached();
+};
+
+/** The hero desk's top face colour. */
+const desk = (page: Page) =>
+  page.evaluate(() => {
+    const top = document.querySelector(".model .block .face.top")!;
+    return getComputedStyle(top).fill;
+  });
+
+const lamp = (page: Page) => page.getByRole("button", { name: "Switch to dark" });
+
+test("the lamp turns the page dark in a wave", async ({ page }) => {
+  await open(page);
+  expect(await page.evaluate(() => document.documentElement.dataset.theme)).toBe("light");
+  expect(await desk(page)).toBe(DESK.light);
+
+  // Read the nearest and farthest hero blocks mid-wave.
+  const mid = await page.evaluate(async () => {
+    const tops = [...document.querySelectorAll<SVGGElement>(".model .block")];
+    document.querySelector<HTMLButtonElement>(".night")!.click();
+    const wave = (g: SVGGElement) => parseFloat(g.style.getPropertyValue("--wave"));
+    tops.sort((a, b) => wave(a) - wave(b));
+    const [near, far] = [tops[0], tops[tops.length - 1]];
+    const fill = (g: SVGGElement) => getComputedStyle(g.querySelector(".face.top")!).fill;
+    // Sample between the near landing and the far start.
+    const gap = (wave(near) + 0.2 + wave(far)) / 2;
+    await new Promise((r) => setTimeout(r, gap * 1000));
+    return {
+      steps: [wave(near), wave(far)],
+      near: [fill(near), near.style.getPropertyValue("--tone-dark")],
+      far: [fill(far), far.style.getPropertyValue("--tone")],
+    };
+  });
+  expect(mid.steps[0] + 0.25).toBeLessThan(mid.steps[1]);
+  expect(mid.steps[1]).toBeLessThanOrEqual(1);
+  const rgb = (hex: string) => `rgb(${[1, 3, 5].map((i) => parseInt(hex.slice(i, i + 2), 16)).join(", ")})`;
+  expect(mid.near[0]).toBe(rgb(mid.near[1]));
+  expect(mid.far[0]).toBe(rgb(mid.far[1]));
+
+  await expect.poll(() => desk(page), { timeout: 1200 }).toBe(DESK.dark);
+  expect(await page.evaluate(() => document.documentElement.dataset.theme)).toBe("dark");
+  await expect(page.getByRole("button", { name: "Switch to light" })).toBeAttached();
+  await expect(page.locator(".night-sky")).toHaveCount(0);
+  await expect(page.locator("html")).toHaveCSS("background-color", "rgb(37, 37, 37)");
+});
+
+test("dark text keeps 4.5:1 against the page", async ({ page }) => {
+  await page.emulateMedia({ colorScheme: "dark" });
+  await open(page);
+  const worst = await page.evaluate(() => {
+    const parse = (c: string) => c.match(/[\d.]+/g)!.slice(0, 3).map(Number);
+    const lum = (c: string) => {
+      const [r, g, b] = parse(c).map((v) => {
+        const s = v / 255;
+        return s <= 0.03928 ? s / 12.92 : ((s + 0.055) / 1.055) ** 2.4;
+      });
+      return 0.2126 * r + 0.7152 * g + 0.0722 * b;
+    };
+    const page = lum(getComputedStyle(document.documentElement).backgroundColor);
+    const ratios = [...document.querySelectorAll<HTMLElement>("h1, h2, h3, p, a, li, button")]
+      .filter((el) => el.textContent?.trim() && getComputedStyle(el).color !== "rgba(0, 0, 0, 0)")
+      .map((el) => {
+        const text = lum(getComputedStyle(el).color);
+        return { ratio: (Math.max(text, page) + 0.05) / (Math.min(text, page) + 0.05), text: el.textContent };
+      });
+    return ratios.sort((a, b) => a.ratio - b.ratio)[0];
+  });
+  expect(worst.ratio, String(worst.text)).toBeGreaterThanOrEqual(4.5);
+});
+
+test("the system scheme sets the first theme; the lamp's choice stays", async ({ page }) => {
+  await page.emulateMedia({ colorScheme: "dark" });
+  await open(page);
+  expect(await page.evaluate(() => document.documentElement.dataset.theme)).toBe("dark");
+  expect(await desk(page)).toBe(DESK.dark);
+
+  await page.emulateMedia({ colorScheme: "light" });
+  await expect.poll(() => page.evaluate(() => document.documentElement.dataset.theme)).toBe("light");
+
+  await page.emulateMedia({ reducedMotion: "reduce" });
+  await lamp(page).click();
+  expect(await desk(page)).toBe(DESK.dark);
+  await page.emulateMedia({ colorScheme: "light" });
+  await page.reload();
+  expect(await page.evaluate(() => document.documentElement.dataset.theme)).toBe("dark");
+});
+
+test("reduced motion switches at once", async ({ page }) => {
+  await page.emulateMedia({ reducedMotion: "reduce", colorScheme: "light" });
+  await open(page);
+  await lamp(page).click();
+  expect(await desk(page)).toBe(DESK.dark);
+  await expect(page.locator(".night-sky")).toHaveCount(0);
+});
diff --git a/site/e2e/play.spec.ts b/site/e2e/play.spec.ts
new file mode 100644
index 0000000..e470a1e
--- /dev/null
+++ b/site/e2e/play.spec.ts
@@ -0,0 +1,92 @@
+import { expect, test, type Page } from "@playwright/test";
+
+const TREE = "Open a Markdown file's history in ElyTree.";
+
+/** Opens the board and waits until it has grown. */
+async function open(page: Page): Promise<string[]> {
+  const errors: string[] = [];
+  page.on("pageerror", (e) => errors.push(e.message));
+  page.on("console", (m) => m.type() === "error" && errors.push(m.text()));
+  await page.goto("/");
+  await page.locator("#roads").scrollIntoViewIfNeeded();
+  await expect(page.locator("#roads .stage")).not.toHaveClass(/grow/, { timeout: 10_000 });
+  return errors;
+}
+
+/** Screen centre of a road cell. */
+async function cell(page: Page, at: string) {
+  const box = (await page.locator(`#roads [data-cell="${at}"]:not(.file)`).boundingBox())!;
+  return { x: box.x + box.width / 2, y: box.y + box.height / 2 };
+}
+
+const mark = (page: Page) => page.getByRole("button", { name: "ElyMark file" });
+
+/** Screen point of a grid spot on the desk top. */
+const desk = (page: Page, x: number, y: number) =>
+  page.evaluate(([x, y]) => {
+    const svg = document.querySelector<SVGSVGElement>("#roads .stage")!;
+    const p = new DOMPoint((x - y) * Math.cos(Math.PI / 6) * 28, ((x + y) / 2 - 0.6) * 28).matrixTransform(svg.getScreenCTM()!);
+    return { x: p.x, y: p.y };
+  }, [x, y]);
+
+test("dragging Mark's file down its road reaches ElyTree", async ({ page }) => {
+  const errors = await open(page);
+  const from = (await mark(page).boundingBox())!;
+  const to = await cell(page, "14,12");
+  await page.mouse.move(from.x + from.width / 2, from.y + from.height / 2);
+  await page.mouse.down();
+  await page.mouse.move(to.x, to.y, { steps: 12 });
+  await page.mouse.up();
+  await expect(mark(page)).toHaveAttribute("data-cell", "14,12");
+  await expect(page.locator("#roads .news")).toHaveText(TREE);
+  await expect(page.locator('#roads [data-cell="14,12"]:not(.file)')).toHaveCSS("--tone", "#3d7fe5");
+  expect(errors).toEqual([]);
+});
+
+test("a file dragged onto empty desk stays on its road", async ({ page }) => {
+  const errors = await open(page);
+  const from = (await mark(page).boundingBox())!;
+  const away = await desk(page, 10.5, 8.5);
+  await page.mouse.move(from.x + from.width / 2, from.y + from.height / 2);
+  await page.mouse.down();
+  await page.mouse.move(away.x, away.y);
+  await page.mouse.up();
+  await page.waitForTimeout(500);
+  await expect(mark(page)).toHaveAttribute("data-cell", "5,10");
+  await expect(page.locator("#roads .news")).toHaveText("");
+  expect(errors).toEqual([]);
+});
+
+test("arrow keys walk Mark's file to ElyTree, then reset", async ({ page }) => {
+  const errors = await open(page);
+  await mark(page).focus();
+  for (const key of ["ArrowDown", "ArrowDown", ...Array(9).fill("ArrowRight")])
+    await page.keyboard.press(key);
+  await expect(mark(page)).toHaveAttribute("data-cell", "14,12");
+  await expect(page.locator("#roads .news")).toHaveText(TREE);
+  await page.getByRole("button", { name: "Put the files back" }).click();
+  await expect(mark(page)).toHaveAttribute("data-cell", "5,10");
+  await expect(page.locator("#roads .news")).toHaveText("");
+  expect(errors).toEqual([]);
+});
+
+test.describe("reduced motion", () => {
+  test.use({ reducedMotion: "reduce" });
+
+  test("files stack at ElyPDF and the line says why", async ({ page }) => {
+    const errors = await open(page);
+    const doc = page.getByRole("button", { name: "ElyDoc file" });
+    await doc.focus();
+    await page.keyboard.press("ArrowDown");
+    for (let i = 0; i < 13; i++) await page.keyboard.press("ArrowRight");
+    await page.keyboard.press("ArrowUp");
+    await expect(doc).toHaveAttribute("data-cell", "15,5");
+    await expect(page.locator("#roads .news")).toHaveText("Export to PDF, open it in ElyPDF.");
+    const show = page.getByRole("button", { name: "ElyShow file" });
+    await show.focus();
+    for (const key of ["ArrowDown", "ArrowDown", "ArrowRight", "ArrowRight", "ArrowRight", "ArrowRight", "ArrowRight", "ArrowUp"])
+      await page.keyboard.press(key);
+    await expect(show).toHaveAttribute("data-cell", "15,5");
+    expect(errors).toEqual([]);
+  });
+});
diff --git a/site/e2e/rhythm.spec.ts b/site/e2e/rhythm.spec.ts
new file mode 100644
index 0000000..2124ff2
--- /dev/null
+++ b/site/e2e/rhythm.spec.ts
@@ -0,0 +1,116 @@
+import { expect, test, type Page } from "@playwright/test";
+
+const APPS = ["ElyDoc", "ElyTable", "ElyShow", "ElyPDF", "ElyTree", "ElyMark"];
+
+let errors: string[] = [];
+
+test.beforeEach(async ({ page }) => {
+  errors = [];
+  page.on("pageerror", (e) => errors.push(String(e)));
+  await page.goto("/");
+  await page.locator(".tour .model").scrollIntoViewIfNeeded();
+  await button(page).hover();
+  await page.evaluate(() =>
+    Promise.all(document.querySelector(".tour .model")!.getAnimations({ subtree: true }).map((a) => a.finished)),
+  );
+});
+
+test.afterEach(() => expect(errors).toEqual([]));
+
+const button = (page: Page) => page.locator(".speaker-button");
+const paused = (page: Page) => page.evaluate(() => document.querySelector<HTMLAudioElement>(".tour audio")!.paused);
+
+/** Screen top of each building's first top face. */
+const tops = (page: Page) =>
+  page.evaluate(
+    (apps) =>
+      apps.map((n) => document.querySelector(`.tour .block[data-part="${n}"] .face.top`)!.getBoundingClientRect().top),
+    APPS,
+  );
+
+/** Whether anything dances: hops, road light or a moving woofer. */
+const dancing = (page: Page) =>
+  page.evaluate(() => {
+    const hops = [...document.querySelectorAll<SVGGElement>(".tour .block")].filter((g) =>
+      g.style.getPropertyValue("--hop"),
+    );
+    const moved = [...document.querySelectorAll<SVGGElement>(".tour .woofer")].filter((g) => g.style.translate);
+    return hops.length + document.querySelectorAll(".tour .pulse").length + moved.length;
+  });
+
+test("the speaker plays and pauses the music", async ({ page }) => {
+  await expect(button(page)).toHaveAccessibleName("Play music");
+  await button(page).click();
+  await expect.poll(() => paused(page)).toBe(false);
+  await expect(button(page)).toHaveAccessibleName("Pause music");
+  await button(page).click();
+  await expect.poll(() => paused(page)).toBe(true);
+  await expect(button(page)).toHaveAccessibleName("Play music");
+});
+
+test("buildings hop on the beat; all six on the bar", async ({ page }) => {
+  const rest = await tops(page);
+  await button(page).click();
+  await page.waitForFunction(
+    ([apps, rest]) =>
+      apps.every(
+        (n, i) =>
+          document.querySelector(`.tour .block[data-part="${n}"] .face.top`)!.getBoundingClientRect().top < rest[i] - 10,
+      ),
+    [APPS, rest] as const,
+    { polling: "raf", timeout: 6000 },
+  );
+  await page.waitForFunction(
+    ([apps, rest]) =>
+      apps.filter(
+        (n, i) =>
+          document.querySelector(`.tour .block[data-part="${n}"] .face.top`)!.getBoundingClientRect().top < rest[i] - 10,
+      ).length === 1,
+    [APPS, rest] as const,
+    { polling: "raf", timeout: 6000 },
+  );
+});
+
+test("paused, nothing moves", async ({ page }) => {
+  const rest = await tops(page);
+  await button(page).click();
+  await expect.poll(() => dancing(page)).toBeGreaterThan(0);
+  await button(page).click();
+  await expect.poll(() => paused(page)).toBe(true);
+  await expect.poll(() => dancing(page)).toBe(0);
+  for (let i = 0; i < 4; i++) {
+    expect(await dancing(page)).toBe(0);
+    expect(await tops(page)).toEqual(rest);
+    await page.waitForTimeout(150);
+  }
+});
+
+test.describe("reduced motion", () => {
+  test.use({ reducedMotion: "reduce" });
+
+  test("music plays, buildings stay, the woofer stays out", async ({ page }) => {
+    const rest = await tops(page);
+    await button(page).click();
+    await expect.poll(() => paused(page)).toBe(false);
+    await page.waitForTimeout(1200);
+    expect(await dancing(page)).toBe(0);
+    expect(await tops(page)).toEqual(rest);
+    const push = await page.locator(".tour .woofer").first().evaluate((g) => getComputedStyle(g).translate);
+    expect(push).not.toBe("none");
+  });
+});
+
+test("the desk cell under the pointer rises", async ({ page }) => {
+  const at = await page.evaluate(() => {
+    const svg = document.querySelector<SVGSVGElement>(".tour .stage")!;
+    const [cos, sin, unit, top] = [Math.cos(Math.PI / 6), 0.5, 28, 0.6];
+    const p = new DOMPoint((11.5 - 9.5) * cos * unit, ((11.5 + 9.5) * sin - top) * unit).matrixTransform(
+      svg.getScreenCTM()!,
+    );
+    return { x: p.x, y: p.y };
+  });
+  await page.mouse.move(at.x, at.y);
+  await expect(page.locator(".tour .tile")).toHaveCount(1);
+  await page.mouse.move(at.x, at.y - 600);
+  await expect(page.locator(".tour .tile")).toHaveCount(0);
+});
diff --git a/site/e2e/text.spec.ts b/site/e2e/text.spec.ts
index a088544..5ff9c16 100644
--- a/site/e2e/text.spec.ts
+++ b/site/e2e/text.spec.ts
@@ -61,6 +61,7 @@ test.describe("English locale", () => {
     await page.mouse.move(5, 500);
     await expect(lang).toHaveCSS("opacity", "0");
     await page.keyboard.press("Tab");
+    await page.keyboard.press("Tab");
     await expect(lang).toBeFocused();
     await expect(lang).toHaveCSS("opacity", "1");
   });
@@ -79,9 +80,9 @@ test.describe("English locale", () => {
 
   test("links point at the release and the repository", async ({ page }) => {
     await page.goto("/");
-    await expect(page.locator(".region .get")).toHaveCount(APPS.length);
-    for (const app of APPS) {
-      await expect(page.locator(`#${app.toLowerCase()} .get`)).toHaveAttribute("href", dmg(app));
+    await expect(page.locator(".tour .get")).toHaveCount(APPS.length);
+    for (const [i, app] of APPS.entries()) {
+      await expect(page.locator(".tour .get").nth(i)).toHaveAttribute("href", dmg(app));
     }
     await expect(page.locator("#download ul a")).toHaveText([...APPS, TEXT.en.source]);
     for (const [i, app] of APPS.entries()) {
@@ -103,17 +104,19 @@ test.describe("English locale", () => {
     }
   });
 
-  test("region downloads show on hover or focus", async ({ page }) => {
-    await page.goto("/");
-    for (const app of APPS) {
-      const region = page.locator(`#${app.toLowerCase()}`);
-      const get = region.locator(".get");
-      await region.scrollIntoViewIfNeeded();
-      await page.mouse.move(0, 0);
+  test("each app's copy arrives at its anchor; its download shows on intent", async ({ page }) => {
+    for (const [i, app] of APPS.entries()) {
+      await page.goto(`/#${app.toLowerCase()}`);
+      const article = page.locator(".copy article").nth(i);
+      await expect(article).toHaveClass(/current/);
+      await expect(page.locator(".copy article.current")).toHaveCount(1);
+      await expect(page.locator(".rail a").nth(i)).toHaveAttribute("aria-current", "step");
+      const get = article.locator(".get");
+      await page.mouse.move(1000, 5);
       await expect(get).toHaveCSS("opacity", "0");
-      await region.locator("h2").hover();
+      await article.locator("h2").hover();
       await expect(get).toHaveCSS("opacity", "1");
-      await page.locator(".lang").hover();
+      await page.mouse.move(1000, 5);
       await expect(get).toHaveCSS("opacity", "0");
       await get.focus();
       await expect(get).toHaveCSS("opacity", "1");
diff --git a/site/e2e/touch.spec.ts b/site/e2e/touch.spec.ts
index 114284f..dcc3b20 100644
--- a/site/e2e/touch.spec.ts
+++ b/site/e2e/touch.spec.ts
@@ -5,12 +5,13 @@ const APPS = ["ElyDoc", "ElyTable", "ElyShow", "ElyPDF", "ElyTree", "ElyMark"];
 
 test.use({ reducedMotion: "reduce" });
 
-/** Screen top of the building's first block, in SVG pixels. */
+/** Building top over the desk top, in SVG pixels; camera-free. */
 const top = (page: Page, name: string) =>
   page.evaluate((n) => {
-    const svg = document.querySelector<SVGSVGElement>(".hero .stage")!;
+    const svg = document.querySelector<SVGSVGElement>(".model .stage")!;
     const scale = svg.getBoundingClientRect().width / svg.viewBox.baseVal.width;
-    return (document.querySelector(`.block[data-part="${n}"]`)!.getBoundingClientRect().top + scrollY) / scale;
+    const at = (sel: string) => document.querySelector(sel)!.getBoundingClientRect().top;
+    return (at(`.block[data-part="${n}"]`) - at('.block[data-part=""]')) / scale;
   }, name);
 
 /** A point that hits the building; `low` picks the lowest. */
@@ -38,7 +39,7 @@ const spot = (page: Page, name: string, low = false) =>
     [name, low] as const,
   );
 
-const caption = (page: Page, name: string) => page.locator(".caption", { hasText: name });
+const caption = (page: Page, name: string) => page.locator(".tour .caption", { hasText: name });
 
 let errors: string[] = [];
 
@@ -46,7 +47,7 @@ test.beforeEach(async ({ page }) => {
   errors = [];
   page.on("pageerror", (e) => errors.push(String(e)));
   await page.goto("/");
-  await expect(page.locator(".hero .hit-face:not(.ground)").first()).toBeAttached();
+  await expect(page.locator(".model .hit-face:not(.ground)").first()).toBeAttached();
 });
 
 test.afterEach(() => expect(errors).toEqual([]));
@@ -59,7 +60,7 @@ test("six links in reading order; reduced motion skips growth", async ({ page })
 
 test("focus lifts one cell, shows the name, survives the mouse", async ({ page }) => {
   const rest = await top(page, "ElyDoc");
-  for (let i = 0; i < 3; i++) await page.keyboard.press("Tab");
+  await page.locator(".doors a").first().focus();
   await expect(page.locator(".doors a").first()).toBeFocused();
   expect(rest - (await top(page, "ElyDoc"))).toBeCloseTo(CELL, 0);
   await expect(caption(page, "ElyDoc")).toHaveCSS("opacity", "1");
@@ -89,7 +90,7 @@ test("hover at the bottom edge holds still", async ({ page }) => {
 
 test("the hit owner is the block you see", async ({ page }) => {
   const wrong = await page.evaluate(() => {
-    const r = document.querySelector(".hero .stage")!.getBoundingClientRect();
+    const r = document.querySelector(".model .stage")!.getBoundingClientRect();
     const out: string[] = [];
     const owner = (x: number, y: number) => {
       const face = document.elementsFromPoint(x, y).find((e) => e.classList.contains("face"));
@@ -120,6 +121,8 @@ test("a primary press sinks one cell; only a click starting on it opens", async
 
   await page.evaluate(() => history.replaceState(null, "", "/"));
   await page.evaluate(() => scrollTo(0, 0));
+  // The camera settles on the next frame.
+  await page.evaluate(() => new Promise((r) => requestAnimationFrame(() => requestAnimationFrame(r))));
   const again = await spot(page, "ElyShow");
   await page.mouse.click(again.x, again.y, { button: "right" });
   await page.mouse.move(5, 5);
@@ -131,7 +134,7 @@ test("a primary press sinks one cell; only a click starting on it opens", async
 
 test("holding Enter sinks the focused building until release", async ({ page }) => {
   const rest = await top(page, "ElyDoc");
-  for (let i = 0; i < 3; i++) await page.keyboard.press("Tab");
+  await page.locator(".doors a").first().focus();
   await page.keyboard.down("Enter");
   expect(await top(page, "ElyDoc")).toBeCloseTo(rest, 0);
   await expect(page).toHaveURL(/#elydoc$/);
diff --git a/site/e2e/tour.spec.ts b/site/e2e/tour.spec.ts
new file mode 100644
index 0000000..c618259
--- /dev/null
+++ b/site/e2e/tour.spec.ts
@@ -0,0 +1,111 @@
+import { expect, test, type Page } from "@playwright/test";
+
+const APPS = ["ElyDoc", "ElyTable", "ElyShow", "ElyPDF", "ElyTree", "ElyMark"];
+
+let errors: string[] = [];
+
+test.beforeEach(async ({ page }) => {
+  errors = [];
+  page.on("pageerror", (e) => errors.push(String(e)));
+});
+
+test.afterEach(() => expect(errors).toEqual([]));
+
+const frame = (page: Page) => page.evaluate(() => new Promise((r) => requestAnimationFrame(() => requestAnimationFrame(r))));
+
+/** Scrolls to `spans` stage heights into the tour. */
+async function at(page: Page, spans: number) {
+  await page.evaluate((s) => {
+    document.documentElement.style.scrollBehavior = "auto";
+    scrollTo(0, s * document.querySelector<HTMLElement>(".pin")!.clientHeight);
+  }, spans);
+  await frame(page);
+}
+
+/** Largest gap in px between clip and face corners. */
+const drift = (page: Page, i: number) =>
+  page.evaluate((i) => {
+    const video = document.querySelectorAll<HTMLVideoElement>(".clip")[i];
+    const world = video.parentElement!;
+    const host = world.parentElement!.getBoundingClientRect();
+    const m = new DOMMatrix(getComputedStyle(world).transform).multiply(new DOMMatrix(getComputedStyle(video).transform));
+    const [w, h] = [video.offsetWidth, video.offsetHeight];
+    const clip = [[0, 0], [w, 0], [w, h], [0, h]].map(([x, y]) => m.transformPoint(new DOMPoint(x, y)));
+    const row = (k: number) => document.querySelector<SVGGElement>(`.block.slab[data-app="${i}"][data-row="${k}"]`)!;
+    const ctm = row(0).ownerSVGElement!.getScreenCTM()!;
+    const corners = (g: SVGGElement) =>
+      g.querySelector(".face.left")!.getAttribute("points")!.split(" ").map((p) => {
+        const [x, y] = p.split(",").map(Number);
+        return new DOMPoint(x, y).matrixTransform(ctm);
+      });
+    // Left face points: bottom-left, bottom-right, top-right, top-left.
+    const [bl, br] = corners(row(0));
+    const [, , tr, tl] = corners(row(3));
+    const face = [tl, tr, br, bl];
+    return Math.max(...clip.map((p, k) => Math.hypot(p.x + host.left - face[k].x, p.y + host.top - face[k].y)));
+  }, i);
+
+test("each clip stays on its screen face, held or gliding", async ({ page }) => {
+  await page.goto("/");
+  for (const [i] of APPS.entries()) {
+    for (const s of [i + 1, i + 1.5]) {
+      await at(page, s);
+      await page.waitForTimeout(800);
+      expect(await drift(page, i), `${APPS[i]} at ${s}`).toBeLessThan(1);
+    }
+  }
+});
+
+test("only the current app's clip loads and plays", async ({ page }) => {
+  await page.goto("/");
+  await at(page, 3);
+  const clips = page.locator(".clip");
+  await expect.poll(() => clips.nth(2).evaluate((v: HTMLVideoElement) => !v.paused && v.currentTime > 0)).toBe(true);
+  for (const i of [0, 1, 3, 4, 5]) await expect(clips.nth(i).locator("source")).toHaveCount(0);
+  await at(page, 4);
+  await expect(clips.nth(2).locator("source")).toHaveCount(0);
+  await expect.poll(() => clips.nth(3).evaluate((v: HTMLVideoElement) => !v.paused)).toBe(true);
+  await at(page, 0);
+  await expect(page.locator(".clip source")).toHaveCount(0);
+});
+
+test("the rail scrolls to an app and marks it", async ({ page }) => {
+  await page.goto("/");
+  await at(page, 1);
+  await page.locator(".rail a").nth(4).click();
+  await expect(page.locator(".rail a").nth(4)).toHaveAttribute("aria-current", "step");
+  await expect(page.locator(".copy article.current h2")).toHaveText("ElyTree");
+});
+
+test.describe("reduced motion", () => {
+  test.use({ reducedMotion: "reduce" });
+
+  test("clips wait for a press; the camera jumps", async ({ page }) => {
+    await page.goto("/#elyshow");
+    const clip = page.locator(".clip").nth(2);
+    await expect(page.locator(".copy article.current h2")).toHaveText("ElyShow");
+    await expect(clip).toHaveAttribute("poster", "/clips/show.jpg");
+    expect(await clip.evaluate((v: HTMLVideoElement) => v.paused)).toBe(true);
+    const held = await page.evaluate(() => getComputedStyle(document.querySelector(".world")!).transform);
+    await at(page, 3.4);
+    expect(await page.evaluate(() => getComputedStyle(document.querySelector(".world")!).transform)).toBe(held);
+    await page.locator(".copy article.current .toggle-clip").click();
+    await expect.poll(() => clip.evaluate((v: HTMLVideoElement) => !v.paused)).toBe(true);
+    await expect(page.locator(".copy article.current .toggle-clip")).toHaveText("Pause");
+  });
+});
+
+test.describe("phone", () => {
+  test.use({ viewport: { width: 390, height: 844 } });
+
+  test("no sideways scroll; copy sits below the stage", async ({ page }) => {
+    await page.goto("/");
+    for (const s of [0, 1, 2.5, 4, 6, 7]) {
+      await at(page, s);
+      expect(await page.evaluate(() => document.documentElement.scrollWidth)).toBe(390);
+    }
+    await at(page, 2);
+    const copy = await page.locator(".copy article.current").boundingBox();
+    expect(copy!.y).toBeGreaterThan(844 * 0.55);
+  });
+});
diff --git a/site/public/clips/doc.jpg b/site/public/clips/doc.jpg
new file mode 100644
index 0000000..13dfd90
Binary files /dev/null and b/site/public/clips/doc.jpg differ
diff --git a/site/public/clips/doc.mp4 b/site/public/clips/doc.mp4
new file mode 100644
index 0000000..228bac5
Binary files /dev/null and b/site/public/clips/doc.mp4 differ
diff --git a/site/public/clips/doc.webm b/site/public/clips/doc.webm
new file mode 100644
index 0000000..f439f9e
Binary files /dev/null and b/site/public/clips/doc.webm differ
diff --git a/site/public/clips/mark.jpg b/site/public/clips/mark.jpg
new file mode 100644
index 0000000..c213322
Binary files /dev/null and b/site/public/clips/mark.jpg differ
diff --git a/site/public/clips/mark.mp4 b/site/public/clips/mark.mp4
new file mode 100644
index 0000000..40d5d24
Binary files /dev/null and b/site/public/clips/mark.mp4 differ
diff --git a/site/public/clips/mark.webm b/site/public/clips/mark.webm
new file mode 100644
index 0000000..57ee5db
Binary files /dev/null and b/site/public/clips/mark.webm differ
diff --git a/site/public/clips/pdf.jpg b/site/public/clips/pdf.jpg
new file mode 100644
index 0000000..e0f889a
Binary files /dev/null and b/site/public/clips/pdf.jpg differ
diff --git a/site/public/clips/pdf.mp4 b/site/public/clips/pdf.mp4
new file mode 100644
index 0000000..33981ab
Binary files /dev/null and b/site/public/clips/pdf.mp4 differ
diff --git a/site/public/clips/pdf.webm b/site/public/clips/pdf.webm
new file mode 100644
index 0000000..39f5bb7
Binary files /dev/null and b/site/public/clips/pdf.webm differ
diff --git a/site/public/clips/show.jpg b/site/public/clips/show.jpg
new file mode 100644
index 0000000..0a4daed
Binary files /dev/null and b/site/public/clips/show.jpg differ
diff --git a/site/public/clips/show.mp4 b/site/public/clips/show.mp4
new file mode 100644
index 0000000..59840c4
Binary files /dev/null and b/site/public/clips/show.mp4 differ
diff --git a/site/public/clips/show.webm b/site/public/clips/show.webm
new file mode 100644
index 0000000..1aefbca
Binary files /dev/null and b/site/public/clips/show.webm differ
diff --git a/site/public/clips/table.jpg b/site/public/clips/table.jpg
new file mode 100644
index 0000000..0b6a533
Binary files /dev/null and b/site/public/clips/table.jpg differ
diff --git a/site/public/clips/table.mp4 b/site/public/clips/table.mp4
new file mode 100644
index 0000000..2c2e907
Binary files /dev/null and b/site/public/clips/table.mp4 differ
diff --git a/site/public/clips/table.webm b/site/public/clips/table.webm
new file mode 100644
index 0000000..32b38f5
Binary files /dev/null and b/site/public/clips/table.webm differ
diff --git a/site/public/clips/tree.jpg b/site/public/clips/tree.jpg
new file mode 100644
index 0000000..4f6f65d
Binary files /dev/null and b/site/public/clips/tree.jpg differ
diff --git a/site/public/clips/tree.mp4 b/site/public/clips/tree.mp4
new file mode 100644
index 0000000..9fdb96f
Binary files /dev/null and b/site/public/clips/tree.mp4 differ
diff --git a/site/public/clips/tree.webm b/site/public/clips/tree.webm
new file mode 100644
index 0000000..7db801a
Binary files /dev/null and b/site/public/clips/tree.webm differ
diff --git a/site/public/film/ely-office.mp4 b/site/public/film/ely-office.mp4
new file mode 100644
index 0000000..2bf2b86
Binary files /dev/null and b/site/public/film/ely-office.mp4 differ
diff --git a/site/public/film/poster.jpg b/site/public/film/poster.jpg
new file mode 100644
index 0000000..e0a6633
Binary files /dev/null and b/site/public/film/poster.jpg differ
diff --git a/site/public/music/ely.m4a b/site/public/music/ely.m4a
new file mode 100644
index 0000000..907a9ef
Binary files /dev/null and b/site/public/music/ely.m4a differ
diff --git a/site/public/music/ely.ogg b/site/public/music/ely.ogg
new file mode 100644
index 0000000..ca8a1a3
Binary files /dev/null and b/site/public/music/ely.ogg differ
diff --git a/site/src/film.css b/site/src/film.css
new file mode 100644
index 0000000..8798d55
--- /dev/null
+++ b/site/src/film.css
@@ -0,0 +1,91 @@
+.film {
+  display: grid;
+  justify-items: center;
+  gap: 2.5rem;
+  max-width: 72rem;
+  margin: 0 auto;
+  padding: 9rem 1.5rem;
+  text-align: center;
+}
+
+.film-stage {
+  position: relative;
+  width: 100%;
+}
+
+.film-stage .stage {
+  width: min(100%, 52rem, calc(78svh * var(--ratio)));
+  margin: 0 auto;
+  transition: opacity 0.3s ease-out;
+}
+
+.film.flat .stage {
+  opacity: 0;
+}
+
+.film .notch {
+  fill: #fff;
+}
+
+.film video {
+  position: absolute;
+  display: block;
+  transform-origin: 0 0;
+  object-fit: fill;
+  background: #000;
+  outline: var(--bezel) solid color-mix(in oklab, #3a3a3c, black 9%);
+  cursor: pointer;
+}
+
+.film.flat video {
+  cursor: auto;
+}
+
+/* The bezel matches the screen's left face at night. */
+:root[data-theme="dark"] .film video:not(:focus-visible) {
+  outline-color: color-mix(in oklab, #303032, black 9%);
+}
+
+.film video:focus-visible {
+  outline-color: var(--accent);
+}
+
+/* The film appears once its screen has landed. */
+.film:not(.seen) video,
+.film:not(.seen) .film-play {
+  visibility: hidden;
+}
+
+.film.seen video {
+  animation: shown 0.2s ease-out var(--shown) backwards;
+}
+
+@keyframes shown {
+  from {
+    opacity: 0;
+  }
+}
+
+.film-play {
+  position: absolute;
+  padding: 0;
+  border: 0;
+  background: none;
+  color: transparent;
+  font-size: 0;
+  cursor: pointer;
+}
+
+.film.flat .film-play {
+  visibility: hidden;
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .film-stage .stage {
+    transition: none;
+  }
+
+  .film.seen video {
+    animation: none;
+  }
+}
diff --git a/site/src/film.ts b/site/src/film.ts
new file mode 100644
index 0000000..657cc9f
--- /dev/null
+++ b/site/src/film.ts
@@ -0,0 +1,178 @@
+// The film on a block screen; it flattens to play.
+import { block, project, stage, UNIT } from "./iso.ts";
+import { grow } from "./beat.ts";
+import { ACCENT } from "./model.ts";
+import { said } from "./text.ts";
+import "./film.css";
+
+const SVG = "http://www.w3.org/2000/svg";
+const PLINTH = "#e6e6e2";
+const DARK = "#3a3a3c";
+const MORPH = 520;
+const EASE = "cubic-bezier(0.2, 0.8, 0.3, 1)";
+
+/** The screen; the film fills its left face. */
+const SCREEN = { x: 4, y: 1, z: 1.6, w: 16.8, d: 0.8, h: 9.8, tone: DARK };
+const BEZEL = 0.4;
+
+/** The film on the face: corner, across, down. */
+function face(): [number, number][] {
+  const x = SCREEN.x + BEZEL;
+  const y = SCREEN.y + SCREEN.d;
+  const z = SCREEN.z + SCREEN.h - BEZEL;
+  const corner = project(x, y, z);
+  const across = project(x + 16, y, z);
+  const down = project(x, y, z - 9);
+  return [corner, [across[0] - corner[0], across[1] - corner[1]], [down[0] - corner[0], down[1] - corner[1]]];
+}
+
+/** A play triangle on a block's left face. */
+function notch(g: SVGGElement, x: number, y: number, z: number, w: number, h: number): void {
+  const p = (dx: number, dz: number) => project(x + dx * w, y, z + dz * h).map((v) => v.toFixed(2)).join(",");
+  const tri = document.createElementNS(SVG, "polygon");
+  tri.setAttribute("points", [p(0.32, 0.8), p(0.32, 0.2), p(0.74, 0.5)].join(" "));
+  tri.setAttribute("class", "notch");
+  g.append(tri);
+}
+
+function scene(): { svg: SVGSVGElement; prop: SVGGElement } {
+  const plinth = block({ x: 0, y: 0, w: 22, d: 5.2, h: 0.8, tone: PLINTH });
+  const feet = [5.5, 18.5].map((x) => block({ x, y: 1.1, z: 0.8, w: 1, d: 0.6, h: 0.8, tone: DARK }));
+  const screen = block(SCREEN);
+  const spec = { x: 0.6, y: 2.4, z: 0.8, w: 2.4, d: 2.2, h: 1.6, tone: ACCENT };
+  const prop = block(spec);
+  notch(prop, spec.x, spec.y + spec.d, spec.z, spec.w, spec.h);
+  grow([[plinth], [...feet, screen], [prop]]);
+  const svg = stage([plinth, ...feet, screen, prop]);
+  svg.classList.add("grow");
+  svg.setAttribute("aria-hidden", "true");
+  svg.style.setProperty("--step", `${UNIT * 0.5}px`);
+  svg.style.setProperty("--ratio", String(svg.viewBox.baseVal.width / svg.viewBox.baseVal.height));
+  return { svg, prop };
+}
+
+/** A screen on a plinth that becomes a player. */
+export function film(): HTMLElement {
+  const section = document.createElement("section");
+  section.id = "film";
+  section.className = "film";
+  const { svg, prop } = scene();
+  const land = prop.style.getPropertyValue("--land");
+  section.style.setProperty("--shown", land);
+
+  const host = document.createElement("div");
+  host.className = "film-stage";
+  const video = document.createElement("video");
+  video.src = "/film/ely-office.mp4";
+  video.poster = "/film/poster.jpg";
+  video.preload = "none";
+  video.playsInline = true;
+  const play = said("button", "filmPlay");
+  play.className = "film-play";
+  host.append(svg, video, play);
+  const line = said("p", "filmLine");
+  line.id = "film-line";
+  video.setAttribute("aria-labelledby", line.id);
+  section.append(host, line);
+
+  const reduced = matchMedia("(prefers-reduced-motion: reduce)");
+  let flat = false;
+  let onFace = "none";
+  let morph: Animation | undefined;
+
+  const layout = () => {
+    const box = host.getBoundingClientRect();
+    const art = svg.getBoundingClientRect();
+    const vb = svg.viewBox.baseVal;
+    const k = art.width / vb.width;
+    const w = Math.floor(Math.min((box.width * 16) / (16 + 2 * BEZEL), (box.height * 16) / (9 + 2 * BEZEL)));
+    const h = Math.round((w * 9) / 16);
+    const left = (box.width - w) / 2;
+    const top = (box.height - h) / 2;
+    Object.assign(video.style, { width: `${w}px`, height: `${h}px`, left: `${left}px`, top: `${top}px` });
+    video.style.setProperty("--bezel", `${(w * BEZEL) / 16}px`);
+    const [corner, across, down] = face();
+    const ox = art.left - box.left + (corner[0] - vb.x) * k - left;
+    const oy = art.top - box.top + (corner[1] - vb.y) * k - top;
+    onFace = `matrix(${(across[0] * k) / w}, ${(across[1] * k) / w}, ${(down[0] * k) / h}, ${(down[1] * k) / h}, ${ox}, ${oy})`;
+    if (!flat && !morph) video.style.transform = onFace;
+    const p = prop.getBoundingClientRect();
+    Object.assign(play.style, {
+      left: `${p.left - box.left}px`,
+      top: `${p.top - box.top}px`,
+      width: `${p.width}px`,
+      height: `${p.height}px`,
+    });
+  };
+
+  const move = (to: string) => {
+    const from = getComputedStyle(video).transform;
+    morph?.cancel();
+    video.style.transform = to;
+    if (reduced.matches) return;
+    morph = video.animate([{ transform: from }, { transform: to }], { duration: MORPH, easing: EASE });
+    const own = morph;
+    own.onfinish = () => {
+      if (morph !== own) return;
+      morph = undefined;
+      if (!flat) video.style.transform = onFace;
+    };
+  };
+
+  const open = () => {
+    if (flat) return;
+    flat = true;
+    section.classList.add("flat");
+    video.controls = true;
+    move("none");
+    host.scrollIntoView({ block: "center", behavior: reduced.matches ? "instant" : "smooth" });
+    video.focus({ preventScroll: true });
+    video.play().catch((error: unknown) => {
+      if (error instanceof DOMException && error.name === "AbortError") return;
+      throw error;
+    });
+  };
+
+  const close = () => {
+    if (!flat) return;
+    flat = false;
+    section.classList.remove("flat");
+    video.pause();
+    video.controls = false;
+    move(onFace);
+    play.focus({ preventScroll: true });
+  };
+
+  play.addEventListener("click", open);
+  video.addEventListener("click", () => {
+    if (!flat) open();
+  });
+  video.addEventListener("ended", close);
+  document.addEventListener("keydown", (e) => {
+    if (flat && e.key === "Escape") close();
+  });
+
+  const lift = (up: boolean, press = false) => {
+    prop.classList.toggle("lifted", up);
+    prop.classList.toggle("pressed", up && press);
+  };
+  play.addEventListener("pointerenter", () => lift(true));
+  play.addEventListener("pointerleave", () => lift(play.matches(":focus-visible")));
+  play.addEventListener("focus", () => lift(true));
+  play.addEventListener("blur", () => lift(false));
+  play.addEventListener("pointerdown", () => lift(true, true));
+  play.addEventListener("pointerup", () => lift(true));
+
+  new ResizeObserver(layout).observe(host);
+  new IntersectionObserver(
+    (entries, seen) => {
+      if (!entries.some((e) => e.isIntersecting)) return;
+      svg.classList.add("seen");
+      section.classList.add("seen");
+      video.preload = "metadata";
+      seen.disconnect();
+    },
+    { rootMargin: "50% 0px" },
+  ).observe(section);
+  return section;
+}
diff --git a/site/src/iso.css b/site/src/iso.css
index 14d3284..356775e 100644
--- a/site/src/iso.css
+++ b/site/src/iso.css
@@ -1,15 +1,24 @@
 /* One colour, three tones; no shadows. */
+.block {
+  --ink: var(--tone);
+}
+
+/* At night a block takes its dark tone. */
+:root[data-theme="dark"] .block {
+  --ink: var(--tone-dark, var(--tone));
+}
+
 .face.top {
-  fill: var(--tone);
+  fill: var(--ink);
 }
 
 .face.left,
 .face.outline {
-  fill: color-mix(in oklab, var(--tone), black 9%);
+  fill: color-mix(in oklab, var(--ink), black 9%);
 }
 
 .face.right {
-  fill: color-mix(in oklab, var(--tone), black 20%);
+  fill: color-mix(in oklab, var(--ink), black 20%);
 }
 
 /* Each block drops one step and lands on its beat. */
diff --git a/site/src/main.ts b/site/src/main.ts
index f0976f1..1a21842 100644
--- a/site/src/main.ts
+++ b/site/src/main.ts
@@ -1,50 +1,43 @@
 import "./style.css";
 import "./iso.css";
-import { block, stage } from "./iso.ts";
-import { grow } from "./beat.ts";
+import "./tour.css";
+import { tour } from "./tour.ts";
+import { props, reveal } from "./regions.ts";
+import { night } from "./night.ts";
+import { rhythm } from "./rhythm.ts";
+import { playground } from "./play.ts";
+import { film } from "./film.ts";
 import { model } from "./model.ts";
-import { touch } from "./touch.ts";
-import { regions, reveal } from "./regions.ts";
 import { said, speak, type Lang } from "./text.ts";
 
 const REPO = "https://github.com/ZacharyZhang-NY/ElyOffice";
 const RELEASE = `${REPO}/releases/download/v0.1.0`;
+const APPS = model.slice(1, -1).map((p) => p.name);
 
 const app = document.querySelector<HTMLElement>("#app");
 if (!app) throw new Error("index.html has no #app");
 
-const apps = model.slice(1, -1);
-const built = model.map((part) => part.blocks.map(block));
-grow(built);
-const parts = new Map(apps.map((p) => [p.name, built[model.indexOf(p)]]));
-
 const hero = document.createElement("header");
-hero.className = "hero";
 const title = document.createElement("h1");
 title.textContent = "Ely Office";
-const host = document.createElement("div");
-host.className = "model";
-const svg = stage(built.flat());
-svg.classList.add("grow", "seen");
-svg.setAttribute("aria-hidden", "true");
-host.append(svg);
 const github = document.createElement("a");
 github.href = REPO;
 github.textContent = "GitHub";
-hero.append(title, said("p", "tagline"), said("p", "platforms"), github, host);
-touch(host, svg, parts);
+hero.append(title, said("p", "tagline"), said("p", "platforms"), github);
+const { section, host, svg } = tour(hero);
+rhythm(host, svg);
 
-const sections = regions();
+const shelf = props();
 
 const footer = document.createElement("footer");
 footer.id = "download";
 const version = document.createElement("h2");
 version.textContent = "Ely Office 0.1.0";
 const list = document.createElement("ul");
-for (const p of apps) {
+for (const name of APPS) {
   const a = document.createElement("a");
-  a.href = `${RELEASE}/${p.name}-0.1.0-arm64.dmg`;
-  a.textContent = p.name;
+  a.href = `${RELEASE}/${name}-0.1.0-arm64.dmg`;
+  a.textContent = name;
   const li = document.createElement("li");
   li.append(a);
   list.append(li);
@@ -59,13 +52,16 @@ footer.append(version, said("p", "platforms"), said("p", "needs"), said("p", "un
 const toggle = said("button", "other");
 toggle.className = "lang";
 let lang: Lang = navigator.language.toLowerCase().startsWith("zh") ? "zh" : "en";
-toggle.addEventListener("click", () => {
-  lang = lang === "en" ? "zh" : "en";
+/** Writes the page in `next`; the toggle names the other. */
+const say = (next: Lang) => {
+  lang = next;
   speak(lang);
-});
+  toggle.lang = lang === "en" ? "zh-CN" : "en";
+};
+toggle.addEventListener("click", () => say(lang === "en" ? "zh" : "en"));
 
 const main = document.createElement("main");
-main.append(...sections);
-app.append(toggle, hero, main, footer);
-speak(lang);
-reveal(sections);
+main.append(section, playground(), shelf, film());
+app.append(night(), toggle, main, footer);
+say(lang);
+reveal([shelf]);
diff --git a/site/src/night.css b/site/src/night.css
new file mode 100644
index 0000000..3f87a99
--- /dev/null
+++ b/site/src/night.css
@@ -0,0 +1,73 @@
+/* Night: soft greys, never black; the accent stays. */
+:root[data-theme="dark"] {
+  color-scheme: dark;
+  color: #f5f5f7;
+  background: #252525;
+  --quiet: #c4c2c0;
+}
+
+/* The accent passes 4.5:1 as text only when lighter. */
+:root[data-theme="dark"] {
+  --link: #78a6ee;
+}
+
+/* Faces and words re-tone as the wave reaches them. */
+.waving .face {
+  transition: fill 0.2s ease-out var(--wave, 0s);
+}
+
+.waving :is(h1, h2, h3, p, a, li, button) {
+  transition: color 0.2s ease-out var(--wave, 0s);
+}
+
+.night-sky {
+  position: fixed;
+  inset: 0;
+  z-index: -1;
+  pointer-events: none;
+}
+
+.night {
+  position: fixed;
+  top: 1rem;
+  left: 1.5rem;
+  z-index: 1;
+  padding: 0.25rem;
+  border: 0;
+  background: none;
+  cursor: pointer;
+  opacity: 0;
+  transition: opacity 0.15s ease-out;
+}
+
+.night .stage {
+  width: 2.5rem;
+  height: auto;
+}
+
+.night:hover,
+.night:focus-visible,
+body:has(.hero:hover) .night {
+  opacity: 1;
+}
+
+@media (hover: none) {
+  .night {
+    opacity: 1;
+  }
+}
+
+.night-name {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  overflow: hidden;
+  clip-path: inset(50%);
+  white-space: nowrap;
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .night {
+    transition: none;
+  }
+}
diff --git a/site/src/night.ts b/site/src/night.ts
new file mode 100644
index 0000000..7fc418b
--- /dev/null
+++ b/site/src/night.ts
@@ -0,0 +1,163 @@
+// A desk lamp that turns the page dark and back.
+import "./night.css";
+import { block, stage } from "./iso.ts";
+import { TEXT, type Lang } from "./text.ts";
+
+const SIXTEENTH = 60 / 112 / 4;
+/** Wave steps; the last block lands by 1.14 s. */
+const STEPS = 7;
+const LAND = 0.2;
+const KEY = "ely-theme";
+const PAGE = { light: "#fbfbfa", dark: "#252525" };
+
+type Theme = keyof typeof PAGE;
+
+/** Light tone to night tone, by the same three-face rule. */
+export const NIGHT: Record<string, string> = {
+  "#f4f4f2": "#5c5c5a",
+  "#e6e6e2": "#3a3a3a",
+  "#3a3a3c": "#303032",
+  "#3d7fe5": "#3d7fe5",
+};
+const GLOW = "#f2e6c9";
+const DESK = "#e6e6e2";
+const PAPER = "#f4f4f2";
+
+/** Gives every block under `root` its night tone. */
+function tone(root: ParentNode): void {
+  const blocks = [...root.querySelectorAll<SVGGElement>("g.block")];
+  if (root instanceof SVGGElement && root.matches("g.block")) blocks.push(root);
+  for (const g of blocks) {
+    if (g.style.getPropertyValue("--tone-dark")) continue;
+    const light = g.style.getPropertyValue("--tone").trim().toLowerCase();
+    const dark = NIGHT[light];
+    if (!dark) throw new Error(`no night tone for ${light}`);
+    g.style.setProperty("--tone-dark", dark);
+  }
+}
+
+function stored(): Theme | null {
+  try {
+    const v = localStorage.getItem(KEY);
+    return v === "dark" || v === "light" ? v : null;
+  } catch {
+    return null;
+  }
+}
+
+function keep(theme: Theme): void {
+  try {
+    localStorage.setItem(KEY, theme);
+  } catch {
+    // Storage may be off; the choice lasts this page.
+  }
+}
+
+/** Base, post, arm, shade, bulb and a pool of light. */
+function lamp(): SVGSVGElement {
+  const glow = [
+    block({ x: 0.9, y: 0.1, z: 0.2, w: 0.8, d: 0.8, h: 0.04, tone: DESK }),
+    block({ x: 1.1, y: 0.3, z: 0.95, w: 0.4, d: 0.4, h: 0.35, tone: DESK }),
+  ];
+  for (const g of glow) g.style.setProperty("--tone-dark", GLOW);
+  const svg = stage([
+    block({ x: 0, y: 0, w: 1.8, d: 1.8, h: 0.2, tone: DESK }),
+    glow[0],
+    block({ x: 0.2, y: 0.35, z: 0.2, w: 0.35, d: 0.3, h: 2.0, tone: PAPER }),
+    block({ x: 0.55, y: 0.35, z: 1.9, w: 0.75, d: 0.3, h: 0.3, tone: PAPER }),
+    glow[1],
+    block({ x: 0.95, y: 0.15, z: 1.3, w: 0.7, d: 0.7, h: 0.6, tone: PAPER }),
+  ]);
+  svg.setAttribute("aria-hidden", "true");
+  return svg;
+}
+
+const lang = (): Lang => (document.documentElement.lang.startsWith("zh") ? "zh" : "en");
+
+let run = 0;
+
+/** Turns the page to `theme`, rippling out from `from`. */
+function turn(theme: Theme, from: DOMRect | null): void {
+  const root = document.documentElement;
+  const before = root.dataset.theme;
+  if (before === theme) return;
+  const still = !from || !before || matchMedia("(prefers-reduced-motion: reduce)").matches;
+  const id = ++run;
+  root.querySelector(".night-sky")?.remove();
+  if (still) {
+    root.classList.remove("waving");
+    root.style.removeProperty("background-color");
+    root.dataset.theme = theme;
+    return;
+  }
+  const x = from.x + from.width / 2;
+  const y = from.y + from.height / 2;
+  const corner = Math.max(...[0, innerWidth].flatMap((cx) => [0, innerHeight].map((cy) => Math.hypot(cx - x, cy - y))));
+  const all = [...document.querySelectorAll<HTMLElement | SVGElement>("g.block, h1, h2, h3, p, a, li, button")];
+  const away = all.map((el) => {
+    const r = el.getBoundingClientRect();
+    const seen = r.bottom > 0 && r.top < innerHeight && r.right > 0 && r.left < innerWidth;
+    return { el, seen, d: Math.hypot(r.x + r.width / 2 - x, r.y + r.height / 2 - y) };
+  });
+  // The farthest thing in view lands on the last step.
+  const reach = Math.max(1, ...away.filter((a) => a.seen).map((a) => a.d));
+  for (const { el, d } of away) {
+    const step = Math.min(STEPS, Math.round((d / reach) * STEPS));
+    el.style.setProperty("--wave", `${(step * SIXTEENTH).toFixed(3)}s`);
+  }
+  // The new sky spreads at the wave's pace.
+  const sky = document.createElement("div");
+  sky.className = "night-sky";
+  sky.style.background = PAGE[theme];
+  root.style.backgroundColor = PAGE[before as Theme];
+  document.body.append(sky);
+  root.classList.add("waving");
+  root.dataset.theme = theme;
+  const last = STEPS * SIXTEENTH;
+  const span = last + LAND;
+  const circle = (r: number) => ({ clipPath: `circle(${r.toFixed(1)}px at ${x}px ${y}px)` });
+  const grown = sky.animate(
+    [circle(0), { ...circle(Math.min(reach, corner)), offset: last / span }, circle(corner)],
+    { duration: span * 1000, easing: "linear", fill: "forwards" },
+  );
+  grown.finished.then(() => {
+    if (id !== run) return;
+    sky.remove();
+    root.style.removeProperty("background-color");
+    root.classList.remove("waving");
+  });
+}
+
+/** The lamp button; it follows the system until pressed. */
+export function night(): HTMLElement {
+  const button = document.createElement("button");
+  button.className = "night";
+  const name = document.createElement("span");
+  name.className = "night-name";
+  button.append(lamp(), name);
+
+  const label = () => {
+    const key = document.documentElement.dataset.theme === "dark" ? "light" : "dark";
+    name.dataset.t = key;
+    name.textContent = TEXT[lang()][key];
+  };
+  const system = matchMedia("(prefers-color-scheme: dark)");
+  const set = (theme: Theme, from: DOMRect | null) => {
+    turn(theme, from);
+    label();
+  };
+
+  tone(document);
+  new MutationObserver((changes) => {
+    for (const c of changes) for (const n of c.addedNodes) if (n instanceof Element) tone(n);
+  }).observe(document.documentElement, { childList: true, subtree: true });
+
+  set(stored() ?? (system.matches ? "dark" : "light"), null);
+  system.addEventListener("change", () => stored() || set(system.matches ? "dark" : "light", button.getBoundingClientRect()));
+  button.addEventListener("click", () => {
+    const theme = document.documentElement.dataset.theme === "dark" ? "light" : "dark";
+    keep(theme);
+    set(theme, button.getBoundingClientRect());
+  });
+  return button;
+}
diff --git a/site/src/play.css b/site/src/play.css
new file mode 100644
index 0000000..1abec20
--- /dev/null
+++ b/site/src/play.css
@@ -0,0 +1,91 @@
+.play {
+  display: grid;
+  justify-items: center;
+  gap: 4rem;
+  max-width: 64rem;
+  margin: 0 auto;
+  padding: 9rem 1.5rem;
+  text-align: center;
+}
+
+.play .board {
+  position: relative;
+  width: 100%;
+}
+
+.play .stage {
+  width: 100%;
+  user-select: none;
+  -webkit-user-select: none;
+}
+
+.play .caption {
+  translate: -50% -100%;
+}
+
+.play:hover .caption,
+.play:focus-within .caption {
+  opacity: 1;
+}
+
+@media (hover: none) {
+  .play .caption {
+    opacity: 1;
+  }
+}
+
+.file {
+  cursor: grab;
+  touch-action: none;
+  outline: none;
+}
+
+.file:active {
+  cursor: grabbing;
+}
+
+.file:focus-visible .face.outline {
+  stroke: #1d1d1f;
+  stroke-width: 2;
+  stroke-linejoin: round;
+}
+
+:root[data-theme="dark"] .file:focus-visible .face.outline {
+  stroke: #f4f4f2;
+}
+
+.play .foot {
+  display: grid;
+  justify-items: center;
+  gap: 1.5rem;
+  min-height: 5.5rem;
+}
+
+.again {
+  padding: 0.5rem 0.75rem;
+  border: 0;
+  background: none;
+  font: inherit;
+  font-size: 1.0625rem;
+  color: var(--link);
+  cursor: pointer;
+  opacity: 0;
+  transition: opacity 0.15s ease-out;
+}
+
+.play:hover .again,
+.again:focus-visible {
+  opacity: 1;
+}
+
+@media (hover: none) {
+  .again {
+    opacity: 1;
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .again {
+    transition: none;
+  }
+}
diff --git a/site/src/play.ts b/site/src/play.ts
new file mode 100644
index 0000000..38ba04e
--- /dev/null
+++ b/site/src/play.ts
@@ -0,0 +1,458 @@
+// Roads: drag a file from its app to its target.
+import "./play.css";
+import { block, order, project, stage, UNIT, type Block } from "./iso.ts";
+import { ACCENT, model } from "./model.ts";
+import { said, TEXT, type Key } from "./text.ts";
+
+type Cell = [number, number];
+
+const BEAT = 60 / 112;
+const STEP = BEAT / 4;
+const TOP = 0.6;
+const RISE = 0.1;
+const FILE = 0.56;
+const THICK = 0.36;
+const DESK = "#e6e6e2";
+const PAPER = "#f4f4f2";
+const ROAD = "#d3d3ce";
+const ROAD_NIGHT = "#474745";
+const REACH = 0.9;
+
+/** Each building's back corner on the board. */
+const HOMES: Record<string, Cell> = {
+  ElyDoc: [1, 1],
+  ElyTable: [5, 1],
+  ElyShow: [9, 1],
+  ElyPDF: [14, 1],
+  ElyMark: [1, 9],
+  ElyTree: [13, 11],
+};
+
+/** Cells along straight runs between corners. */
+function walk(...corners: Cell[]): Cell[] {
+  const out: Cell[] = [corners[0]];
+  for (const [x, y] of corners.slice(1)) {
+    let [cx, cy] = out[out.length - 1];
+    if (cx !== x && cy !== y) throw new Error("roads turn at right angles");
+    while (cx !== x || cy !== y) {
+      cx += Math.sign(x - cx);
+      cy += Math.sign(y - cy);
+      out.push([cx, cy]);
+    }
+  }
+  return out;
+}
+
+interface Link {
+  from: string;
+  to: string;
+  line: Key;
+  path: Cell[];
+}
+
+const LINKS: Link[] = [
+  { from: "ElyDoc", to: "ElyPDF", line: "toPdf", path: walk([2, 5], [2, 6], [15, 6], [15, 5]) },
+  { from: "ElyTable", to: "ElyPDF", line: "toPdf", path: walk([6, 5], [6, 6], [15, 6], [15, 5]) },
+  { from: "ElyShow", to: "ElyPDF", line: "toPdf", path: walk([10, 4], [10, 6], [15, 6], [15, 5]) },
+  { from: "ElyMark", to: "ElyPDF", line: "toPdf", path: walk([5, 10], [5, 6], [15, 6], [15, 5]) },
+  { from: "ElyMark", to: "ElyTree", line: "toTree", path: walk([5, 10], [5, 12], [14, 12]) },
+];
+
+const SOURCES = ["ElyDoc", "ElyTable", "ElyShow", "ElyMark"] as const;
+const NAMES: Record<(typeof SOURCES)[number], Key> = {
+  ElyDoc: "fileDoc",
+  ElyTable: "fileTable",
+  ElyShow: "fileShow",
+  ElyMark: "fileMark",
+};
+
+/** Arrows as screen directions; ties take this grid step. */
+const ARROWS: Record<string, [number, number, Cell]> = {
+  ArrowRight: [1, 0, [1, 0]],
+  ArrowLeft: [-1, 0, [-1, 0]],
+  ArrowUp: [0, -1, [0, -1]],
+  ArrowDown: [0, 1, [0, 1]],
+};
+
+const id = (c: Cell) => `${c[0]},${c[1]}`;
+const same = (a: Cell, b: Cell) => a[0] === b[0] && a[1] === b[1];
+const still = () => matchMedia("(prefers-reduced-motion: reduce)").matches;
+const lang = () => (document.documentElement.lang === "zh-CN" ? "zh" : "en");
+
+interface File {
+  name: string;
+  start: Cell;
+  cell: Cell;
+  goal: Cell;
+  level: number;
+  done: boolean;
+  wrap: SVGGElement;
+  links: Link[];
+  ways: Set<string>;
+}
+
+interface Item {
+  el: SVGGElement;
+  box: () => Required<Block>;
+}
+
+/** A building moved home; accent is kept for files. */
+function placed(name: string): Required<Block>[] {
+  const part = model.find((p) => p.name === name);
+  if (!part) throw new Error(`no building ${name}`);
+  const [x, y] = HOMES[name];
+  const left = Math.min(...part.blocks.map((b) => b.x));
+  const back = Math.min(...part.blocks.map((b) => b.y));
+  const floor = Math.min(...part.blocks.map((b) => b.z));
+  const snap = (v: number) => Math.round(v * 1000) / 1000;
+  return part.blocks.map((b) => ({ ...b, tone: PAPER, x: snap(b.x - left + x), y: snap(b.y - back + y), z: snap(b.z - floor + TOP) }));
+}
+
+const fileBox = (f: File): Required<Block> => ({
+  x: f.cell[0] + (1 - FILE) / 2,
+  y: f.cell[1] + (1 - FILE) / 2,
+  z: TOP + RISE + f.level * THICK,
+  w: FILE,
+  d: FILE,
+  h: THICK,
+  tone: ACCENT,
+});
+
+/** The roads section: board, files, and one line. */
+export function playground(): HTMLElement {
+  const section = document.createElement("section");
+  section.id = "roads";
+  section.className = "play";
+  const names = document.createElement("div");
+  names.hidden = true;
+  const hint = said("span", "moveHint");
+  hint.id = "roads-hint";
+  names.append(hint);
+
+  const items: Item[] = [];
+  const add = (spec: Required<Block>) => {
+    const g = block(spec);
+    items.push({ el: g, box: () => spec });
+    return g;
+  };
+  const desk = add({ x: 0, y: 0, z: 0, w: 17.5, d: 13.5, h: TOP, tone: DESK });
+  const buildings = new Map(Object.keys(HOMES).map((n) => [n, placed(n).map(add)]));
+  const roads = new Map<string, SVGGElement>();
+  for (const cell of LINKS.flatMap((l) => l.path)) {
+    if (roads.has(id(cell))) continue;
+    const g = add({ x: cell[0] + 0.05, y: cell[1] + 0.05, z: TOP, w: 0.9, d: 0.9, h: RISE, tone: ROAD });
+    paint(g, ROAD, ROAD_NIGHT);
+    g.dataset.cell = id(cell);
+    roads.set(id(cell), g);
+  }
+
+  const files: File[] = SOURCES.map((name) => {
+    const links = LINKS.filter((l) => l.from === name);
+    const start = links[0].path[0];
+    const wrap = document.createElementNS("http://www.w3.org/2000/svg", "g");
+    wrap.setAttribute("class", "file");
+    wrap.setAttribute("tabindex", "0");
+    wrap.setAttribute("role", "button");
+    const label = said("span", NAMES[name]);
+    label.id = `roads-${name}`;
+    names.append(label);
+    wrap.setAttribute("aria-labelledby", label.id);
+    wrap.setAttribute("aria-describedby", hint.id);
+    const f: File = {
+      name, start, cell: start, goal: start, level: 0, done: false, wrap, links,
+      ways: new Set(links.flatMap((l) => l.path.map(id))),
+    };
+    items.push({ el: wrap, box: () => fileBox(f) });
+    return f;
+  });
+  files.forEach(render);
+
+  const svg = stage(items.flatMap((i) => (i.el.classList.contains("file") ? [] : [i.el])));
+  svg.classList.add("grow");
+  svg.style.setProperty("--step", `${UNIT}px`);
+  const total = timed(desk, buildings, roads, files);
+
+  const board = document.createElement("div");
+  board.className = "board";
+  board.append(svg, ...captions(svg, buildings));
+
+  const news = document.createElement("p");
+  news.className = "news";
+  news.setAttribute("aria-live", "polite");
+  const again = said("button", "putBack");
+  again.className = "again";
+  again.type = "button";
+  again.hidden = true;
+  const foot = document.createElement("div");
+  foot.className = "foot";
+  foot.append(news, again);
+  section.append(said("h2", "roads"), board, foot, names);
+
+  let ready = false;
+  const timers = new Set<number>();
+  const later = (ms: number, run: () => void) => {
+    const t = window.setTimeout(() => {
+      timers.delete(t);
+      run();
+    }, ms);
+    timers.add(t);
+  };
+  const grown = () => {
+    svg.classList.remove("grow");
+    ready = true;
+  };
+  if (still()) grown();
+  const seen = new IntersectionObserver((entries) => {
+    if (!entries.some((e) => e.isIntersecting)) return;
+    seen.disconnect();
+    svg.classList.add("seen");
+    if (!ready) window.setTimeout(grown, total * 1000 + 250);
+  }, { rootMargin: "0px 0px -20% 0px" });
+  seen.observe(section);
+
+  /** Painter order; `fixed` keeps its DOM place and focus. */
+  const arrange = (fixed: SVGGElement | null) => {
+    const els = order(items.map((i) => i.box())).map((i) => items[i].el);
+    const at = fixed ? els.indexOf(fixed) : -1;
+    if (!fixed || at < 0) return svg.append(...els);
+    for (const el of els.slice(0, at)) svg.insertBefore(el, fixed);
+    svg.append(...els.slice(at + 1));
+  };
+  arrange(null);
+
+  let walking: SVGGElement | null = null;
+  const step = (f: File, next: Cell) => {
+    for (const o of files) {
+      if (o === f || !same(o.cell, f.cell) || o.level < f.level) continue;
+      o.level -= 1;
+      render(o);
+    }
+    f.level = files.filter((o) => o !== f && same(o.cell, next)).length;
+    f.cell = next;
+    render(f);
+    arrange(f.wrap);
+    again.hidden = false;
+    if (!still()) {
+      f.wrap.animate([{ translate: `0 -${UNIT}px` }, { translate: "0 0" }], {
+        duration: STEP * 1000,
+        easing: "cubic-bezier(0.2, 0.8, 0.3, 1)",
+      });
+      click();
+    }
+    const link = f.links.find((l) => same(l.path[l.path.length - 1], next));
+    if (link) arrive(f, link);
+  };
+
+  const tick = (f: File) => {
+    walking = null;
+    while (!f.done && !same(f.cell, f.goal)) {
+      step(f, route(f, f.goal)[1]);
+      if (!still() && !f.done && !same(f.cell, f.goal)) {
+        walking = f.wrap;
+        return later(STEP * 1000, () => tick(f));
+      }
+    }
+  };
+  const go = (f: File, goal: Cell) => {
+    if (f.done || same(goal, f.goal)) return;
+    f.goal = goal;
+    if (walking !== f.wrap) tick(f);
+  };
+
+  const arrive = (f: File, link: Link) => {
+    f.done = true;
+    f.goal = f.cell;
+    news.dataset.t = link.line;
+    news.textContent = TEXT[lang()][link.line];
+    link.path.forEach((cell, i) => {
+      const g = roads.get(id(cell))!;
+      const light = () => paint(g, ACCENT, ACCENT);
+      if (still()) light();
+      else later((i + 1) * STEP * 1000, light);
+    });
+    if (still()) return;
+    const house = buildings.get(link.to)!;
+    for (const b of house) b.classList.add("lifted");
+    later(BEAT * 1000, () => house.forEach((b) => b.classList.remove("lifted")));
+  };
+
+  again.addEventListener("click", () => {
+    for (const t of timers) clearTimeout(t);
+    timers.clear();
+    walking = null;
+    for (const f of files) Object.assign(f, { cell: f.start, goal: f.start, level: 0, done: false });
+    files.forEach(render);
+    for (const g of roads.values()) paint(g, ROAD, ROAD_NIGHT);
+    for (const b of buildings.values()) b.forEach((g) => g.classList.remove("lifted"));
+    delete news.dataset.t;
+    news.textContent = "";
+    arrange(null);
+    files[files.length - 1].wrap.focus();
+    again.hidden = true;
+  });
+
+  let drag: { f: File; pointer: number; dx: number; dy: number } | null = null;
+  for (const f of files) {
+    f.wrap.addEventListener("pointerdown", (e) => {
+      if (!ready || f.done || e.button !== 0) return;
+      e.preventDefault();
+      f.wrap.focus({ focusVisible: false });
+      wake();
+      svg.setPointerCapture(e.pointerId);
+      const [gx, gy] = grid(svg, e);
+      drag = { f, pointer: e.pointerId, dx: gx - f.cell[0] - 0.5, dy: gy - f.cell[1] - 0.5 };
+    });
+    f.wrap.addEventListener("keydown", (e) => {
+      const arrow = ARROWS[e.key];
+      if (!arrow) return;
+      e.preventDefault();
+      if (!ready || f.done) return;
+      wake();
+      const next = toward(f, f.goal, arrow);
+      if (next) go(f, next);
+    });
+  }
+  svg.addEventListener("pointermove", (e) => {
+    if (!drag || e.pointerId !== drag.pointer) return;
+    const [gx, gy] = grid(svg, e);
+    const near = nearest(drag.f, gx - drag.dx, gy - drag.dy);
+    if (near) go(drag.f, near);
+  });
+  const drop = (e: PointerEvent) => {
+    if (drag && e.pointerId === drag.pointer) drag = null;
+  };
+  svg.addEventListener("pointerup", drop);
+  svg.addEventListener("pointercancel", drop);
+  return section;
+}
+
+/** Sets a road cell's day and night tones. */
+function paint(g: SVGGElement, day: string, night: string): void {
+  g.style.setProperty("--tone", day);
+  g.style.setProperty("--tone-dark", night);
+}
+
+/** Rebuilds the file's block at its cell and level. */
+function render(f: File): void {
+  f.wrap.replaceChildren(block(fileBox(f)));
+  f.wrap.dataset.cell = id(f.cell);
+}
+
+/** Landing times: desk, buildings, roads in waves, then files. */
+function timed(desk: SVGGElement, buildings: Map<string, SVGGElement[]>, roads: Map<string, SVGGElement>, files: File[]): number {
+  let at = BEAT;
+  const land = (gs: SVGGElement[]) => {
+    for (const g of gs) g.style.setProperty("--land", `${at.toFixed(3)}s`);
+    at += STEP;
+  };
+  land([desk]);
+  for (const house of buildings.values()) land(house);
+  const waves = new Map<number, SVGGElement[]>();
+  for (const [key, g] of roads) {
+    const sum = key.split(",").map(Number).reduce((a, b) => a + b);
+    waves.set(sum, [...(waves.get(sum) ?? []), g]);
+  }
+  for (const sum of [...waves.keys()].sort((a, b) => a - b)) land(waves.get(sum)!);
+  land(files.map((f) => f.wrap));
+  return at;
+}
+
+/** Building names above their tops, placed in viewBox percent. */
+function captions(svg: SVGSVGElement, buildings: Map<string, SVGGElement[]>): HTMLElement[] {
+  const view = svg.viewBox.baseVal;
+  return [...buildings.keys()].map((name) => {
+    const blocks = placed(name);
+    const xs = blocks.flatMap((b) => [b.x, b.x + b.w]);
+    const ys = blocks.flatMap((b) => [b.y, b.y + b.d]);
+    const tops = blocks.flatMap((b) => [project(b.x, b.y, b.z + b.h)[1], project(b.x + b.w, b.y, b.z + b.h)[1]]);
+    const [cx] = project((Math.min(...xs) + Math.max(...xs)) / 2, (Math.min(...ys) + Math.max(...ys)) / 2, 0);
+    const p = document.createElement("p");
+    p.className = "caption";
+    p.textContent = name;
+    p.setAttribute("aria-hidden", "true");
+    p.style.left = `${((cx - view.x) / view.width) * 100}%`;
+    p.style.top = `${((Math.min(...tops) - UNIT * 0.5 - view.y) / view.height) * 100}%`;
+    return p;
+  });
+}
+
+/** The pointer on the road plane, in grid units. */
+function grid(svg: SVGSVGElement, e: PointerEvent): [number, number] {
+  const m = svg.getScreenCTM();
+  if (!m) throw new Error("board is not rendered");
+  const p = new DOMPoint(e.clientX, e.clientY).matrixTransform(m.inverse());
+  const [cx, sy] = project(1, 0, 0);
+  const a = p.x / cx;
+  const b = (p.y + (TOP + RISE) * UNIT) / sy;
+  return [(a + b) / 2, (b - a) / 2];
+}
+
+/** Nearest road cell to a grid point, if close. */
+function nearest(f: File, x: number, y: number): Cell | null {
+  let best: Cell | null = null;
+  let far = REACH;
+  for (const key of f.ways) {
+    const cell = key.split(",").map(Number) as Cell;
+    const d = Math.hypot(cell[0] + 0.5 - x, cell[1] + 0.5 - y);
+    if (d < far) [best, far] = [cell, d];
+  }
+  return best;
+}
+
+/** Shortest road from the file to `goal`, ends included. */
+function route(f: File, goal: Cell): Cell[] {
+  const back = new Map<string, Cell | null>([[id(f.cell), null]]);
+  const queue: Cell[] = [f.cell];
+  while (queue.length) {
+    const at = queue.shift()!;
+    if (same(at, goal)) {
+      const path: Cell[] = [];
+      for (let c: Cell | null = at; c; c = back.get(id(c))!) path.unshift(c);
+      return path;
+    }
+    for (const n of around(f, at)) {
+      if (back.has(id(n))) continue;
+      back.set(id(n), at);
+      queue.push(n);
+    }
+  }
+  throw new Error(`no road from ${id(f.cell)} to ${id(goal)}`);
+}
+
+const around = (f: File, [x, y]: Cell): Cell[] =>
+  ([[x + 1, y], [x - 1, y], [x, y + 1], [x, y - 1]] as Cell[]).filter((c) => f.ways.has(id(c)));
+
+/** Road cell beside `from` that best follows an arrow. */
+function toward(f: File, from: Cell, [ax, ay, prefer]: [number, number, Cell]): Cell | null {
+  let best: Cell | null = null;
+  let score = 0.1;
+  for (const n of around(f, from)) {
+    const step: Cell = [n[0] - from[0], n[1] - from[1]];
+    const [sx, sy] = project(step[0], step[1], 0);
+    const s = (sx * ax + sy * ay) / Math.hypot(sx, sy) + (same(step, prefer) ? 0.01 : 0);
+    if (s > score) [best, score] = [n, s];
+  }
+  return best;
+}
+
+let audio: AudioContext | null = null;
+
+/** Starts sound only after the reader touches a file. */
+function wake(): void {
+  if (!audio && !still()) audio = new AudioContext();
+}
+
+/** A short tick for each landing. */
+function click(): void {
+  if (!audio) return;
+  const t = audio.currentTime;
+  const tone = audio.createOscillator();
+  const gain = audio.createGain();
+  tone.type = "triangle";
+  tone.frequency.value = 1320;
+  gain.gain.setValueAtTime(0.04, t);
+  gain.gain.exponentialRampToValueAtTime(0.0001, t + 0.04);
+  tone.connect(gain).connect(audio.destination);
+  tone.start(t);
+  tone.stop(t + 0.05);
+}
diff --git a/site/src/regions.ts b/site/src/regions.ts
index f6480f6..5ac36b0 100644
--- a/site/src/regions.ts
+++ b/site/src/regions.ts
@@ -1,38 +1,10 @@
-// One region per app, then the three props.
-import { block, screen, stage, type Block } from "./iso.ts";
+// Three props: offline, open source, local files.
+import { block, stage } from "./iso.ts";
 import { grow } from "./beat.ts";
-import { model, type Part } from "./model.ts";
 import { said, type Key } from "./text.ts";
 
-const RELEASE = "https://github.com/ZacharyZhang-NY/ElyOffice/releases/download/v0.1.0";
-
 const PAPER = "#f4f4f2";
 const DESK = "#e6e6e2";
-const SCREEN = "#3a3a3c";
-const SHOT = [1440, 810];
-
-/** A part's blocks moved to corner (x, y). */
-function moved(part: Part, x: number, y: number): Required<Block>[] {
-  const left = Math.min(...part.blocks.map((b) => b.x));
-  const back = Math.min(...part.blocks.map((b) => b.y));
-  const floor = Math.min(...part.blocks.map((b) => b.z));
-  const snap = (v: number) => Math.round(v * 1000) / 1000;
-  return part.blocks.map((b) => ({ ...b, x: snap(b.x - left + x), y: snap(b.y - back + y), z: snap(b.z - floor + 0.4) }));
-}
-
-/** A plinth, the app's screen, and its building. */
-function scene(part: Part): SVGSVGElement {
-  const plinth = block({ x: 0, y: 0, w: 11.6, d: 5, h: 0.4, tone: DESK });
-  const slab = block({ x: 0.4, y: 1.2, z: 0.4, w: 7.2, d: 0.25, h: 4.05, tone: SCREEN });
-  screen(slab, `/shots/${part.name.slice(3).toLowerCase()}.jpg`, SHOT[0], SHOT[1]);
-  const house = moved(part, 8.4, 1.2).map(block);
-  grow([[plinth], [slab], house]);
-  const svg = stage([plinth, slab, ...house]);
-  svg.classList.add("grow");
-  svg.setAttribute("role", "img");
-  svg.dataset.shot = part.name;
-  return svg;
-}
 
 const t = (x: number, y: number, z: number, w: number, d: number, h: number, tone = PAPER) =>
   block({ x, y, z, w, d, h, tone });
@@ -78,30 +50,12 @@ function prop(blocks: SVGGElement[], line: Key): HTMLElement {
   return cell;
 }
 
-/** The app regions and the props row. */
-export function regions(): HTMLElement[] {
-  const apps = model.slice(1, -1).map((part) => {
-    const section = document.createElement("section");
-    section.id = part.name.toLowerCase();
-    section.className = "region";
-    const h2 = document.createElement("h2");
-    h2.textContent = part.name;
-    const get = said("a", "download");
-    get.className = "get";
-    get.href = `${RELEASE}/${part.name}-0.1.0-arm64.dmg`;
-    const text = document.createElement("div");
-    text.append(h2, said("p", part.name as Key), get);
-    section.append(scene(part), text);
-    return section;
-  });
-  const props = document.createElement("section");
-  props.className = "props";
-  props.append(
-    prop(cable(), "offline"),
-    prop(box(), "open"),
-    prop(folder(), "local"),
-  );
-  return [...apps, props];
+/** The props row. */
+export function props(): HTMLElement {
+  const row = document.createElement("section");
+  row.className = "props";
+  row.append(prop(cable(), "offline"), prop(box(), "open"), prop(folder(), "local"));
+  return row;
 }
 
 /** Starts each model's growth when it scrolls near. */
diff --git a/site/src/rhythm.css b/site/src/rhythm.css
new file mode 100644
index 0000000..f3a82e7
--- /dev/null
+++ b/site/src/rhythm.css
@@ -0,0 +1,75 @@
+/* The speaker shows on intent and stays while it plays. */
+.stage .block.speaker {
+  animation: none;
+  opacity: 0;
+  transition: opacity 0.2s ease-out;
+}
+
+.model:has(.stage:hover, .speaker-button:hover) .speaker,
+.model:focus-within .speaker,
+.model.playing .speaker {
+  opacity: 1;
+}
+
+@media (hover: none) {
+  .stage .block.speaker {
+    opacity: 1;
+  }
+}
+
+.speaker-button {
+  position: absolute;
+  padding: 0;
+  border: 0;
+  border-radius: 6px;
+  background: none;
+  cursor: pointer;
+}
+
+.speaker-button:focus-visible {
+  outline: 2px solid #3d7fe5;
+  outline-offset: 4px;
+}
+
+.speaker-button span {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  overflow: hidden;
+  clip-path: inset(50%);
+  white-space: nowrap;
+}
+
+/* Buildings hop by their faces; translate stays touch's. */
+.dance > .face {
+  transform: translateY(var(--hop, 0px));
+}
+
+.pulse {
+  fill: color-mix(in oklab, var(--ink), white 60%);
+}
+
+/* The desk cell under the pointer rises a little. */
+.stage .block.tile {
+  animation: none;
+  translate: 0 -6px;
+  transition: translate 0.12s ease-out;
+}
+
+@starting-style {
+  .stage .block.tile {
+    translate: 0 0;
+  }
+}
+
+/* Still, the woofer stays pushed out while it plays. */
+@media (prefers-reduced-motion: reduce) {
+  .stage .block.speaker,
+  .stage .block.tile {
+    transition: none;
+  }
+
+  .model.playing .woofer {
+    translate: -4.85px 2.8px;
+  }
+}
diff --git a/site/src/rhythm.ts b/site/src/rhythm.ts
new file mode 100644
index 0000000..ad169f0
--- /dev/null
+++ b/site/src/rhythm.ts
@@ -0,0 +1,284 @@
+// A desk speaker; the buildings dance to its music.
+import "./rhythm.css";
+import { block, order, project, UNIT, type Block } from "./iso.ts";
+import { ACCENT, model } from "./model.ts";
+import { NIGHT } from "./night.ts";
+import { slab } from "./tour.ts";
+import { TEXT, type Key } from "./text.ts";
+
+type Box = Required<Block>;
+
+const SVG = "http://www.w3.org/2000/svg";
+const BEAT = 60 / 112;
+const STEP = BEAT / 4;
+/** Takeoff on the beat, landing on the eighth. */
+const HOP = 2 * STEP;
+const COS = Math.cos(Math.PI / 6);
+const SIN = Math.sin(Math.PI / 6);
+const DESK = model[0].blocks[0];
+const TOP = DESK.z + DESK.h;
+const APPS = model.slice(1, -1).map((p) => p.name);
+const ROADS = model[model.length - 1].blocks;
+/** Every box the stage draws: the model and the screens. */
+const DRAWN = [...model.flatMap((p) => p.blocks), ...APPS.flatMap(slab)];
+
+/** Cabinet with two cones on its front-left face. */
+const CABINET: Box = { x: 13, y: 8, z: TOP, w: 1.4, d: 1.2, h: 1.9, tone: "#3a3a3c" };
+const CONE = "#e6e6e2";
+const cone = (z: number, s: number, out = 0): Box => ({
+  x: CABINET.x + (CABINET.w - s) / 2, y: CABINET.y + CABINET.d + out, z: TOP + z, w: s, d: 0.14, h: s, tone: CONE,
+});
+const WOOFER = cone(0.25, 0.9);
+const CAP = cone(0.5, 0.4, 0.14);
+const TWEETER = cone(1.35, 0.4);
+/** How far the woofer moves at full level, in cells. */
+const THROW = 0.2;
+
+/** Cuts a road into `n` cells along one axis. */
+function cut(road: Box, n: number, axis: "x" | "y"): Box[] {
+  const long = axis === "x" ? road.w : road.d;
+  return Array.from({ length: n }, (_, i) => {
+    const at = road[axis] + (long * i) / n;
+    return axis === "x" ? { ...road, x: at, w: long / n } : { ...road, y: at, d: long / n };
+  });
+}
+
+/** Light runs along these cells: to ElyPDF, and to ElyTree. */
+const ROUTES = [cut(ROADS[3], 11, "x"), [...cut(ROADS[4], 2, "y"), ...cut(ROADS[5], 3, "x")]];
+
+/** Footprints a desk cell must not touch. */
+const TAKEN = [...DRAWN.filter((b) => b !== DESK), CABINET, WOOFER, CAP, TWEETER];
+
+/** Adds the speaker; the desk dances to its music. */
+export function rhythm(host: HTMLElement, svg: SVGSVGElement): void {
+  const specs = locate(svg);
+  const buildings = APPS.map((name) => {
+    const blocks = [...svg.querySelectorAll<SVGGElement>(`.block[data-part="${name}"]`)];
+    if (!blocks.length) throw new Error(`${name} has no blocks; mount after touch()`);
+    for (const b of blocks) b.classList.add("dance");
+    return { blocks, lift: 0 };
+  });
+  const roads = ROUTES.map((cells) =>
+    cells.map((cell) => ({ cell, g: owner(specs, ROADS.find((r) => inside(cell, r))!) })),
+  );
+
+  const speaker = [CABINET, WOOFER, CAP, TWEETER].map((spec) => {
+    const g = block(spec);
+    paint(g, spec.tone);
+    g.classList.add("speaker");
+    insert(svg, specs, g, spec);
+    return g;
+  });
+  const woofer = speaker.slice(1, 3);
+  for (const g of woofer) g.classList.add("woofer");
+
+  const audio = document.createElement("audio");
+  audio.preload = "none";
+  for (const [src, type] of [["/music/ely.ogg", "audio/ogg; codecs=opus"], ["/music/ely.m4a", "audio/mp4"]]) {
+    const source = document.createElement("source");
+    source.src = src;
+    source.type = type;
+    audio.append(source);
+  }
+
+  const button = document.createElement("button");
+  button.type = "button";
+  button.className = "speaker-button";
+  const name = document.createElement("span");
+  button.append(name);
+  // The button rides the stage's camera, next to it.
+  const world = svg.parentElement;
+  if (!world || getComputedStyle(world).position === "static") throw new Error("stage needs a positioned parent");
+  host.append(audio);
+  world.append(button);
+  const label = (key: Key) => {
+    name.dataset.t = key;
+    name.textContent = TEXT[document.documentElement.lang === "zh-CN" ? "zh" : "en"][key];
+  };
+  label("play");
+
+  const view = svg.viewBox.baseVal;
+  const corners = [CABINET, CAP].flatMap((b) =>
+    [0, 1].flatMap((i) => [0, 1].flatMap((j) => [0, 1].map((k) => project(b.x + i * b.w, b.y + j * b.d, b.z + k * b.h)))),
+  );
+  const [xs, ys] = [corners.map((c) => c[0]), corners.map((c) => c[1])];
+  button.style.left = `${Math.min(...xs) - view.x}px`;
+  button.style.top = `${Math.min(...ys) - view.y}px`;
+  button.style.width = `${Math.max(...xs) - Math.min(...xs)}px`;
+  button.style.height = `${Math.max(...ys) - Math.min(...ys)}px`;
+
+  let level: { analyser: AnalyserNode; data: Float32Array<ArrayBuffer>; peak: number } | null = null;
+  let context: AudioContext | null = null;
+  button.addEventListener("click", async () => {
+    if (!audio.paused) return audio.pause();
+    if (!context) {
+      context = new AudioContext();
+      const analyser = context.createAnalyser();
+      analyser.fftSize = 512;
+      context.createMediaElementSource(audio).connect(analyser).connect(context.destination);
+      level = { analyser, data: new Float32Array(analyser.fftSize), peak: 0 };
+    }
+    await context.resume();
+    await audio.play();
+  });
+
+  const still = matchMedia("(prefers-reduced-motion: reduce)");
+  let frame = 0;
+  let clock = { media: -1, wall: 0 };
+
+  const pulses = ROUTES.map(() => {
+    const p = document.createElementNS(SVG, "polygon");
+    p.setAttribute("class", "pulse");
+    return p;
+  });
+
+  const tick = (now: number) => {
+    frame = requestAnimationFrame(tick);
+    // currentTime updates coarsely; extrapolate between updates.
+    if (audio.currentTime !== clock.media) clock = { media: audio.currentTime, wall: now };
+    const t = clock.media + (now - clock.wall) / 1000;
+    const n = Math.floor(t / BEAT);
+    const into = (t - n * BEAT) / HOP;
+    const lift = into < 1 ? 4 * into * (1 - into) : 0;
+    const bar = Math.floor(n / 4);
+    const who = n % 4 === 0 ? -1 : (bar * 3 + (n % 4) - 1) % APPS.length;
+    buildings.forEach((b, i) => hop(b, who < 0 || who === i ? lift : 0));
+    const cell = Math.floor((t - bar * 4 * BEAT) / STEP);
+    roads.forEach((route, i) => pulse(pulses[i], route[cell] ?? null));
+    if (!level) throw new Error("playing without an analyser");
+    level.analyser.getFloatTimeDomainData(level.data);
+    const peak = level.data.reduce((m, v) => Math.max(m, Math.abs(v)), 0);
+    level.peak = Math.max(peak, level.peak * 0.8);
+    for (const g of woofer) push(g, Math.min(1, level.peak * 1.5) * THROW);
+  };
+
+  const run = () => {
+    const go = !audio.paused && !still.matches && document.visibilityState === "visible";
+    if (go && !frame) frame = requestAnimationFrame(tick);
+    if (go) return;
+    cancelAnimationFrame(frame);
+    frame = 0;
+    for (const b of buildings) hop(b, 0);
+    for (const p of pulses) p.remove();
+    for (const g of woofer) g.style.removeProperty("translate");
+  };
+
+  const playing = (on: boolean) => {
+    host.classList.toggle("playing", on);
+    label(on ? "pause" : "play");
+    for (const g of [speaker[1], speaker[3]]) paint(g, on ? ACCENT : CONE);
+    if (on) lay(null);
+    run();
+  };
+  audio.addEventListener("play", () => playing(true));
+  audio.addEventListener("pause", () => playing(false));
+  audio.addEventListener("ended", () => playing(false));
+  still.addEventListener("change", run);
+  document.addEventListener("visibilitychange", run);
+
+  let tile: { at: string; g: SVGGElement | null } = { at: "", g: null };
+  const lay = (cell: [number, number] | null) => {
+    const at = cell ? cell.join() : "";
+    if (at === tile.at) return;
+    tile.g?.remove();
+    if (tile.g) specs.delete(tile.g);
+    tile = { at, g: null };
+    if (!cell) return;
+    const spec: Box = { x: cell[0], y: cell[1], z: TOP, w: 1, d: 1, h: 0.12, tone: "#f4f4f2" };
+    if (spec.x < 0 || spec.y < 0 || spec.x >= DESK.w || spec.y >= DESK.d) return;
+    if (TAKEN.some((b) => b.x < spec.x + 1 && spec.x < b.x + b.w && b.y < spec.y + 1 && spec.y < b.y + b.d)) return;
+    tile.g = block(spec);
+    paint(tile.g, spec.tone);
+    tile.g.classList.add("tile");
+    insert(svg, specs, tile.g, spec);
+  };
+  svg.addEventListener("pointermove", (e) => {
+    const ground = e.target instanceof SVGElement && e.target.dataset.part === "";
+    if (e.pointerType !== "mouse" || !audio.paused || !ground) return lay(null);
+    const ctm = svg.getScreenCTM();
+    if (!ctm) throw new Error("stage is not rendered");
+    const p = new DOMPoint(e.clientX, e.clientY).matrixTransform(ctm.inverse());
+    // Invert the projection on the desk's top plane.
+    const a = p.x / (COS * UNIT);
+    const b = (p.y / UNIT + TOP) / SIN;
+    lay([Math.floor((a + b) / 2), Math.floor((b - a) / 2)]);
+  });
+  svg.addEventListener("pointerleave", () => lay(null));
+}
+
+/** Sets a block's tone and its night tone. */
+function paint(g: SVGGElement, tone: string) {
+  const dark = NIGHT[tone];
+  if (!dark) throw new Error(`no night tone for ${tone}`);
+  g.style.setProperty("--tone", tone);
+  g.style.setProperty("--tone-dark", dark);
+}
+
+/** Lifts a building by `lift` cells. */
+function hop(b: { blocks: SVGGElement[]; lift: number }, lift: number) {
+  if (lift === b.lift) return;
+  b.lift = lift;
+  for (const g of b.blocks) {
+    if (lift) g.style.setProperty("--hop", `${(-lift * UNIT).toFixed(1)}px`);
+    else g.style.removeProperty("--hop");
+  }
+}
+
+/** Lights one road cell, or none. */
+function pulse(p: SVGPolygonElement, at: { cell: Box; g: SVGGElement } | null) {
+  if (!at) return p.remove();
+  const { x, y, w, d } = at.cell;
+  const z = at.cell.z + at.cell.h;
+  const points = [project(x, y, z), project(x + w, y, z), project(x + w, y + d, z), project(x, y + d, z)];
+  p.setAttribute("points", points.map(([px, py]) => `${px.toFixed(2)},${py.toFixed(2)}`).join(" "));
+  if (p.parentNode !== at.g) at.g.append(p);
+}
+
+/** Pushes the woofer out along its face normal. */
+function push(g: SVGGElement, cells: number) {
+  g.style.translate = `${(-COS * UNIT * cells).toFixed(2)}px ${(SIN * UNIT * cells).toFixed(2)}px`;
+}
+
+function inside(a: Box, b: Box): boolean {
+  return a.x >= b.x && a.y >= b.y && a.x + a.w <= b.x + b.w + 1e-9 && a.y + a.d <= b.y + b.d + 1e-9;
+}
+
+/** Matches drawn blocks to model boxes by top face. */
+function locate(svg: SVGSVGElement): Map<SVGGElement, Box> {
+  const near = (pt: DOMPoint, [x, y]: [number, number]) => Math.abs(pt.x - x) < 0.02 && Math.abs(pt.y - y) < 0.02;
+  const found = new Map<SVGGElement, Box>();
+  for (const g of svg.querySelectorAll<SVGGElement>(".block")) {
+    const top = g.querySelector<SVGPolygonElement>(".face.top");
+    if (!top) throw new Error("block has no top");
+    const spec = DRAWN.find(
+      (b) =>
+        near(top.points[0], project(b.x, b.y, b.z + b.h)) && near(top.points[2], project(b.x + b.w, b.y + b.d, b.z + b.h)),
+    );
+    if (!spec) throw new Error("stage has a block the model lacks");
+    found.set(g, spec);
+  }
+  return found;
+}
+
+function owner(specs: Map<SVGGElement, Box>, spec: Box): SVGGElement {
+  const g = [...specs].find(([, s]) => s === spec)?.[0];
+  if (!g) throw new Error("road is not drawn");
+  return g;
+}
+
+/** Inserts `g` after what it covers, before its coverers. */
+function insert(svg: SVGSVGElement, specs: Map<SVGGElement, Box>, g: SVGGElement, spec: Box) {
+  const drawn = [...svg.querySelectorAll<SVGGElement>(".block")];
+  let last = -1;
+  let first = drawn.length;
+  drawn.forEach((b, i) => {
+    const s = specs.get(b);
+    if (!s) throw new Error("stage has an unknown block");
+    if (order([spec, s])[0] === 1) last = i;
+    else if (order([s, spec])[0] === 1) first = Math.min(first, i);
+  });
+  if (last >= first) throw new Error("no paint slot for the block");
+  if (last >= 0) drawn[last].after(g);
+  else drawn[first].before(g);
+  specs.set(g, spec);
+}
diff --git a/site/src/style.css b/site/src/style.css
index c47dbe1..c4f0114 100644
--- a/site/src/style.css
+++ b/site/src/style.css
@@ -2,9 +2,11 @@
   color-scheme: light;
   font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", sans-serif;
   color: #1d1d1f;
-  background: #fbfbfa;
+  --page: #fbfbfa;
+  background: var(--page);
   --quiet: #6e6e73;
   --accent: #3d7fe5;
+  --link: #2a6ad0;
 }
 
 body {
@@ -35,7 +37,7 @@ p {
 }
 
 a {
-  color: var(--accent);
+  color: var(--link);
   text-decoration: none;
 }
 
@@ -50,7 +52,7 @@ button:focus-visible {
   display: grid;
   justify-items: center;
   gap: 1.25rem;
-  padding: 10rem 1.5rem 9rem;
+  padding: 7rem 1.5rem 0;
   text-align: center;
 }
 
@@ -58,10 +60,6 @@ button:focus-visible {
   font-size: 1.0625rem;
 }
 
-.hero .model {
-  margin-top: 6rem;
-}
-
 .stage {
   display: block;
   max-width: 100%;
@@ -74,51 +72,6 @@ button:focus-visible {
   max-width: 100%;
 }
 
-.region {
-  display: grid;
-  grid-template-columns: 1.6fr 1fr;
-  align-items: center;
-  gap: 6rem;
-  max-width: 72rem;
-  margin: 0 auto;
-  padding: 9rem 1.5rem;
-}
-
-.region > svg {
-  width: 100%;
-}
-
-.region:nth-child(even) {
-  grid-template-columns: 1fr 1.6fr;
-}
-
-.region:nth-child(even) > svg {
-  order: 2;
-}
-
-.region div {
-  display: grid;
-  gap: 1rem;
-  justify-items: start;
-}
-
-.get {
-  font-size: 1.0625rem;
-  opacity: 0;
-  transition: opacity 0.15s ease-out;
-}
-
-.region:hover .get,
-.region:focus-within .get {
-  opacity: 1;
-}
-
-@media (hover: none) {
-  .get {
-    opacity: 1;
-  }
-}
-
 .props {
   display: grid;
   grid-template-columns: repeat(3, 1fr);
@@ -186,23 +139,14 @@ body:has(.hero:hover) .lang {
 }
 
 @media (max-width: 760px) {
-  .region,
   .props {
     grid-template-columns: 1fr;
     gap: 3rem;
     padding: 6rem 1.5rem;
   }
 
-  .region:nth-child(even) {
-    grid-template-columns: 1fr;
-  }
-
-  .region:nth-child(even) > svg {
-    order: 0;
-  }
-
   .hero {
-    padding: 7rem 1.5rem 6rem;
+    padding-top: 5rem;
   }
 }
 
@@ -235,7 +179,6 @@ body:has(.hero:hover) .lang {
 
 @media (prefers-reduced-motion: reduce) {
   .caption,
-  .get,
   .lang {
     transition: none;
   }
diff --git a/site/src/text.ts b/site/src/text.ts
index 2acb763..93722d3 100644
--- a/site/src/text.ts
+++ b/site/src/text.ts
@@ -19,6 +19,23 @@ const en = {
   source: "Source code",
   shot: "screenshot",
   other: "中文",
+  roads: "Drag a file down the road.",
+  fileDoc: "ElyDoc file",
+  fileTable: "ElyTable file",
+  fileShow: "ElyShow file",
+  fileMark: "ElyMark file",
+  moveHint: "Arrow keys move it along the road.",
+  toTree: "Open a Markdown file's history in ElyTree.",
+  toPdf: "Export to PDF, open it in ElyPDF.",
+  putBack: "Put the files back",
+  play: "Play music",
+  pause: "Pause music",
+  filmPlay: "Play the film",
+  filmLine: "90 seconds. Real use, no mockups.",
+  dark: "Switch to dark",
+  light: "Switch to light",
+  clipPlay: "Play",
+  clipPause: "Pause",
 };
 
 const zh: typeof en = {
@@ -39,6 +56,23 @@ const zh: typeof en = {
   source: "源代码",
   shot: "截图",
   other: "English",
+  roads: "把文件沿着路拖过去。",
+  fileDoc: "ElyDoc 文件",
+  fileTable: "ElyTable 文件",
+  fileShow: "ElyShow 文件",
+  fileMark: "ElyMark 文件",
+  moveHint: "方向键沿路移动它。",
+  toTree: "在 ElyTree 里看这份 Markdown 的历史。",
+  toPdf: "导出 PDF，在 ElyPDF 打开。",
+  putBack: "把文件放回去",
+  play: "播放音乐",
+  pause: "暂停音乐",
+  filmPlay: "播放影片",
+  filmLine: "90 秒，全部是真实操作。",
+  dark: "切换到深色",
+  light: "切换到浅色",
+  clipPlay: "播放",
+  clipPause: "暂停",
 };
 
 export type Key = keyof typeof en;
diff --git a/site/src/tour.css b/site/src/tour.css
new file mode 100644
index 0000000..198dc9e
--- /dev/null
+++ b/site/src/tour.css
@@ -0,0 +1,248 @@
+/* One stage pins while the camera visits each app. */
+.tour {
+  --span: 100svh;
+  position: relative;
+  height: calc(var(--span) * 8);
+}
+
+@media (prefers-reduced-motion: no-preference) {
+  html {
+    scroll-behavior: smooth;
+  }
+}
+
+.pin {
+  position: sticky;
+  top: 0;
+  height: var(--span);
+  overflow: clip;
+}
+
+.pin .hero {
+  position: absolute;
+  inset: 0 0 auto;
+  z-index: 1;
+}
+
+.pin .model {
+  position: absolute;
+  inset: 0;
+  max-width: none;
+}
+
+.world {
+  position: absolute;
+  top: 0;
+  left: 0;
+  transform-origin: 0 0;
+}
+
+.world .stage {
+  max-width: none;
+}
+
+.stop {
+  position: absolute;
+  left: 0;
+  width: 1px;
+  height: 1px;
+}
+
+/* Screen rows land on sixteenths as the reader arrives. */
+.grow .block.slab {
+  animation: none;
+}
+
+.block.slab {
+  opacity: 0;
+  visibility: hidden;
+  translate: 0 calc(-1 * var(--step));
+  transition:
+    opacity 0.1s ease-out,
+    translate 0.1s ease-out,
+    visibility 0s 0.1s;
+}
+
+.block.slab.up {
+  opacity: 1;
+  visibility: visible;
+  translate: 0 0;
+  transition:
+    opacity 0.2s cubic-bezier(0.2, 0.8, 0.3, 1) var(--at),
+    translate 0.2s cubic-bezier(0.2, 0.8, 0.3, 1) var(--at);
+}
+
+.clip {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 320px;
+  height: 180px;
+  object-fit: fill;
+  transform-origin: 0 0;
+  cursor: pointer;
+  opacity: 0;
+  visibility: hidden;
+  transition:
+    opacity 0.1s ease-out,
+    visibility 0s 0.1s;
+}
+
+.clip.up {
+  opacity: 1;
+  visibility: visible;
+  transition: opacity 0.2s ease-out var(--at);
+}
+
+/* The copy owns a plain strip beside the model. */
+.copy {
+  position: absolute;
+  inset: 0 auto 0 0;
+  z-index: 1;
+  display: grid;
+  align-items: center;
+  box-sizing: border-box;
+  width: 38%;
+  padding: 0 3vw 0 7vw;
+  background: var(--page);
+  translate: -100% 0;
+  transition: translate 0.2s cubic-bezier(0.2, 0.8, 0.3, 1);
+}
+
+.touring .copy {
+  translate: 0 0;
+}
+
+:root[data-theme="dark"] {
+  --page: #252525;
+}
+
+.copy article {
+  display: grid;
+  grid-area: 1 / 1;
+  gap: 1rem;
+  justify-items: start;
+  align-content: center;
+  opacity: 0;
+  visibility: hidden;
+  transition:
+    opacity 0.15s ease-out,
+    visibility 0s 0.15s;
+}
+
+.copy article.current {
+  opacity: 1;
+  visibility: visible;
+  transition: opacity 0.2s ease-out 0.1s;
+}
+
+.acts {
+  display: flex;
+  gap: 2rem;
+  align-items: baseline;
+}
+
+.get,
+.toggle-clip {
+  font-size: 1.0625rem;
+  opacity: 0;
+  transition: opacity 0.15s ease-out;
+}
+
+.toggle-clip {
+  padding: 0;
+  border: 0;
+  background: none;
+  font: inherit;
+  font-size: 1.0625rem;
+  font-weight: 300;
+  color: var(--quiet);
+  cursor: pointer;
+}
+
+.copy:hover :is(.get, .toggle-clip),
+.copy article:focus-within :is(.get, .toggle-clip) {
+  opacity: 1;
+}
+
+.rail {
+  position: absolute;
+  top: 50%;
+  right: 2rem;
+  z-index: 1;
+  display: grid;
+  gap: 0.5rem;
+  translate: 0 -50%;
+  opacity: 0;
+  visibility: hidden;
+  transition:
+    opacity 0.15s ease-out,
+    visibility 0s 0.15s;
+}
+
+.touring .rail {
+  opacity: 1;
+  visibility: visible;
+  transition: opacity 0.2s ease-out;
+}
+
+.rail a {
+  display: block;
+  padding: 0.25rem;
+}
+
+.rail .stage {
+  width: 1.25rem;
+}
+
+.rail .block {
+  transition: translate 0.15s ease-out;
+}
+
+.rail a:hover .block,
+.rail a:focus-visible .block {
+  translate: 0 -4px;
+}
+
+.rail a[aria-current] .block {
+  --ink: var(--accent);
+}
+
+@media (hover: none) {
+  .get,
+  .toggle-clip {
+    opacity: 1;
+  }
+}
+
+@media (max-width: 760px) {
+  .copy {
+    inset: 58% 0 0;
+    align-items: start;
+    width: auto;
+    padding: 2rem 1.5rem 0;
+    translate: 0 100%;
+  }
+
+  .rail {
+    top: 30%;
+    right: 0.75rem;
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .copy,
+  .block.slab,
+  .block.slab.up,
+  .clip,
+  .clip.up,
+  .copy article,
+  .copy article.current,
+  .rail,
+  .touring .rail,
+  .rail .block,
+  .get,
+  .toggle-clip {
+    transition: none;
+  }
+}
diff --git a/site/src/tour.ts b/site/src/tour.ts
new file mode 100644
index 0000000..8a36d2a
--- /dev/null
+++ b/site/src/tour.ts
@@ -0,0 +1,348 @@
+// The camera glides from the desk into each app.
+import { block, project, stage, type Block } from "./iso.ts";
+import { grow } from "./beat.ts";
+import { model } from "./model.ts";
+import { touch } from "./touch.ts";
+import { said, TEXT, type Key } from "./text.ts";
+
+const RELEASE = "https://github.com/ZacharyZhang-NY/ElyOffice/releases/download/v0.1.0";
+const SCREEN = "#3a3a3c";
+const DESK = "#e6e6e2";
+const STEP = 60 / 112 / 4;
+const ROWS = 4;
+/** Share of each span the camera holds still, per side. */
+const HOLD = 0.35;
+const CLIP = [320, 180];
+const NARROW = 760;
+const TOP = model[0].blocks[0].h;
+
+const apps = model.slice(1, -1);
+const last = apps.length + 1;
+
+/** Each app's screen: corner x, y, post height, width. */
+const SPOTS: Record<string, [number, number, number, number]> = {
+  ElyDoc: [0.1, 0, 0.5, 4],
+  ElyTable: [4.4, 0, 1.6, 4],
+  ElyShow: [10.8, 0.5, 2.2, 4],
+  ElyPDF: [12, 2.3, 0.3, 4],
+  ElyTree: [5.9, 5.6, 0, 4],
+  ElyMark: [0.7, 4.3, 0.1, 4],
+};
+
+/** An app's post, then its screen rows, bottom up. */
+export function slab(name: string): Required<Block>[] {
+  const spot = SPOTS[name];
+  if (!spot) throw new Error(`no screen for ${name}`);
+  const [x, y, post, w] = spot;
+  const d = 0.2;
+  const row = (w * 9) / 16 / ROWS;
+  const out: Required<Block>[] = [];
+  if (post > 0) out.push({ x: x + w / 2 - 0.1, y, z: TOP, w: 0.2, d, h: post, tone: SCREEN });
+  // Each row sits on the last; sums keep faces flush.
+  let z = TOP + post;
+  for (let i = 0; i < ROWS; i++) {
+    out.push({ x, y, z, w, d, h: row, tone: SCREEN });
+    z += row;
+  }
+  return out;
+}
+
+type Box = [number, number, number, number];
+
+/** Screen bounds of blocks, in SVG units. */
+function bounds(blocks: Required<Block>[]): Box {
+  const points = blocks.flatMap((b) =>
+    [0, 1].flatMap((i) => [0, 1].flatMap((j) => [0, 1].map((k) => project(b.x + i * b.w, b.y + j * b.d, b.z + k * b.h)))),
+  );
+  const xs = points.map((p) => p[0]);
+  const ys = points.map((p) => p[1]);
+  return [Math.min(...xs), Math.min(...ys), Math.max(...xs), Math.max(...ys)];
+}
+
+/** World point c drawn at screen point a, scale s. */
+interface Cam {
+  s: number;
+  cx: number;
+  cy: number;
+  ax: number;
+  ay: number;
+}
+
+/** Fits `box` into the screen rectangle `area`. */
+function fit(box: Box, area: Box, most: number): Cam {
+  const s = Math.min((area[2] - area[0]) / (box[2] - box[0]), (area[3] - area[1]) / (box[3] - box[1]), most);
+  return { s, cx: (box[0] + box[2]) / 2, cy: (box[1] + box[3]) / 2, ax: (area[0] + area[2]) / 2, ay: (area[1] + area[3]) / 2 };
+}
+
+const ease = (t: number) => (t < 0.5 ? 4 * t * t * t : 1 - (-2 * t + 2) ** 3 / 2);
+const mix = (a: number, b: number, t: number) => a + (b - a) * t;
+
+function between(a: Cam, b: Cam, t: number): Cam {
+  return {
+    s: Math.exp(mix(Math.log(a.s), Math.log(b.s), t)),
+    cx: mix(a.cx, b.cx, t),
+    cy: mix(a.cy, b.cy, t),
+    ax: mix(a.ax, b.ax, t),
+    ay: mix(a.ay, b.ay, t),
+  };
+}
+
+/** Maps a clip's box onto the screen's left face. */
+function face(rows: Required<Block>[], origin: [number, number]): string {
+  const [first, top] = [rows[0], rows[rows.length - 1]];
+  const y = first.y + first.d;
+  const z = top.z + top.h;
+  const corner = project(first.x, y, z);
+  const across = project(first.x + first.w, y, z);
+  const down = project(first.x, y, first.z);
+  const m = [
+    (across[0] - corner[0]) / CLIP[0],
+    (across[1] - corner[1]) / CLIP[0],
+    (down[0] - corner[0]) / CLIP[1],
+    (down[1] - corner[1]) / CLIP[1],
+    corner[0] - origin[0],
+    corner[1] - origin[1],
+  ];
+  return `matrix(${m.join(", ")})`;
+}
+
+/** A clip that loads only while its app is current. */
+function clip(name: string, transform: string, lands: number): HTMLVideoElement {
+  const video = document.createElement("video");
+  video.className = "clip";
+  video.muted = true;
+  video.defaultMuted = true;
+  video.loop = true;
+  video.playsInline = true;
+  video.preload = "none";
+  video.dataset.src = `/clips/${name.slice(3).toLowerCase()}`;
+  video.style.transform = transform;
+  video.style.setProperty("--at", `${lands.toFixed(3)}s`);
+  video.setAttribute("aria-hidden", "true");
+  return video;
+}
+
+function start(video: HTMLVideoElement): void {
+  if (!video.querySelector("source")) {
+    for (const kind of ["webm", "mp4"]) {
+      const source = document.createElement("source");
+      source.src = `${video.dataset.src}.${kind}`;
+      source.type = `video/${kind}`;
+      video.append(source);
+    }
+  }
+  video.play().catch((e: DOMException) => {
+    // A pause during loading interrupts play; that is expected.
+    if (e.name !== "AbortError") throw e;
+  });
+}
+
+function stop(video: HTMLVideoElement): void {
+  if (!video.querySelector("source")) return;
+  video.pause();
+  video.replaceChildren();
+  video.load();
+}
+
+/** A rail cube for one app. */
+function cube(): SVGSVGElement {
+  const svg = stage([block({ x: 0, y: 0, w: 1, d: 1, h: 0.5, tone: DESK })]);
+  svg.setAttribute("aria-hidden", "true");
+  return svg;
+}
+
+const lang = () => (document.documentElement.lang.startsWith("zh") ? "zh" : "en");
+
+/** Sets a button's keyed text now and on language change. */
+function label(el: HTMLElement, key: Key): void {
+  el.dataset.t = key;
+  el.textContent = TEXT[lang()][key];
+}
+
+/** The pinned tour, starting with `hero` over the whole desk. */
+export function tour(hero: HTMLElement): { section: HTMLElement; host: HTMLElement; svg: SVGSVGElement } {
+  const calm = matchMedia("(prefers-reduced-motion: reduce)");
+  const still = () => calm.matches;
+  const built = model.map((part) => part.blocks.map(block));
+  grow(built);
+  const screens = apps.map((p) => slab(p.name));
+  const shown = screens.map((list, a) =>
+    list.map((b, i) => {
+      const g = block(b);
+      g.classList.add("slab");
+      g.dataset.app = String(a);
+      g.dataset.row = String(i - list.length + ROWS);
+      g.style.setProperty("--at", `${(i * STEP).toFixed(3)}s`);
+      return g;
+    }),
+  );
+  const svg = stage([...built.flat(), ...shown.flat()]);
+  svg.classList.add("grow", "seen");
+  svg.setAttribute("aria-hidden", "true");
+  const view = svg.viewBox.baseVal;
+  // Exact size keeps clips on their faces when zoomed.
+  svg.style.width = `${view.width}px`;
+  svg.style.height = `${view.height}px`;
+  const origin: [number, number] = [view.x, view.y];
+
+  const world = document.createElement("div");
+  world.className = "world";
+  world.append(svg);
+  const host = document.createElement("div");
+  host.className = "model";
+  host.append(world);
+
+  // Screens stay out of the hit layer.
+  const marks = shown.flat().map((g) => {
+    const mark = document.createComment("");
+    g.replaceWith(mark);
+    return [mark, g] as const;
+  });
+  touch(host, svg, new Map(apps.map((p, i) => [p.name, built[i + 1]])));
+  for (const [mark, g] of marks) mark.replaceWith(g);
+
+  const clips = apps.map((p, i) => {
+    const rows = screens[i].filter((b) => b.w > 0.2);
+    return clip(p.name, face(rows, origin), shown[i].length * STEP);
+  });
+  world.append(...clips);
+
+  const plays = clips.map((video) => {
+    const button = document.createElement("button");
+    button.className = "toggle-clip";
+    const sync = () => label(button, video.paused ? "clipPlay" : "clipPause");
+    video.addEventListener("play", sync);
+    video.addEventListener("pause", sync);
+    button.addEventListener("click", () => (video.paused ? start(video) : video.pause()));
+    video.addEventListener("click", () => (video.paused ? start(video) : video.pause()));
+    sync();
+    return button;
+  });
+
+  const copy = document.createElement("div");
+  copy.className = "copy";
+  const articles = apps.map((p, i) => {
+    const article = document.createElement("article");
+    const h2 = document.createElement("h2");
+    h2.textContent = p.name;
+    const get = said("a", "download");
+    get.className = "get";
+    get.href = `${RELEASE}/${p.name}-0.1.0-arm64.dmg`;
+    const acts = document.createElement("div");
+    acts.className = "acts";
+    acts.append(get, plays[i]);
+    article.append(h2, said("p", p.name as Key), acts);
+    return article;
+  });
+  copy.append(...articles);
+
+  const rail = document.createElement("div");
+  rail.className = "rail";
+  const steps = apps.map((p) => {
+    const a = document.createElement("a");
+    a.href = `#${p.name.toLowerCase()}`;
+    a.setAttribute("aria-label", p.name);
+    a.append(cube());
+    return a;
+  });
+  rail.append(...steps);
+
+  const pin = document.createElement("div");
+  pin.className = "pin";
+  hero.classList.add("hero");
+  pin.append(hero, host, copy, rail);
+  const section = document.createElement("section");
+  section.className = "tour";
+  const stops = apps.map((p, i) => {
+    const stop = document.createElement("div");
+    stop.id = p.name.toLowerCase();
+    stop.className = "stop";
+    stop.style.top = `calc(var(--span) * ${i + 1})`;
+    return stop;
+  });
+  section.append(pin, ...stops);
+
+  const desk = bounds(model.flatMap((p) => p.blocks));
+  const homes = apps.map((p, i) => bounds([...p.blocks, ...screens[i]]));
+  let top = 0;
+  let span = 1;
+  let cams: Cam[] = [];
+  let current = -1;
+  let queued = false;
+
+  const measure = () => {
+    const [w, h] = [pin.clientWidth, pin.clientHeight];
+    top = section.getBoundingClientRect().top + scrollY;
+    span = h;
+    const below = hero.offsetTop + hero.offsetHeight + 32;
+    const whole = fit(desk, [24, below, w - 24, h - 32], 2);
+    const area: Box = w <= NARROW ? [16, h * 0.04, w - 52, h * 0.56] : [w * 0.42, h * 0.08, w - 88, h * 0.92];
+    cams = [whole, ...homes.map((box) => fit(box, area, 8)), whole];
+  };
+
+  const choose = (next: number) => {
+    if (next === current) return;
+    if (current >= 0) {
+      for (const g of shown[current]) g.classList.remove("up");
+      clips[current].classList.remove("up");
+      stop(clips[current]);
+      articles[current].classList.remove("current");
+      steps[current].removeAttribute("aria-current");
+    }
+    current = next;
+    pin.classList.toggle("touring", current >= 0);
+    if (current < 0) return;
+    for (const g of shown[current]) g.classList.add("up");
+    for (const i of [current - 1, current, current + 1]) {
+      if (clips[i] && !clips[i].poster) clips[i].poster = `${clips[i].dataset.src}.jpg`;
+    }
+    clips[current].classList.add("up");
+    articles[current].classList.add("current");
+    steps[current].setAttribute("aria-current", "step");
+    if (!still() && !document.hidden) start(clips[current]);
+  };
+
+  const render = () => {
+    queued = false;
+    // The first measure comes with the first layout.
+    if (!cams.length) return;
+    const p = Math.min(Math.max((scrollY - top) / span, 0), last);
+    const k = Math.min(Math.floor(p), last - 1);
+    const f = p - k;
+    let cam: Cam;
+    if (still()) cam = cams[Math.round(p)];
+    // Leaving the hero, the desk moves at once.
+    else if (k === 0 && f < 1 - HOLD) cam = between(cams[0], cams[1], ease(f / (1 - HOLD)));
+    else if (f <= HOLD) cam = cams[k];
+    else if (f >= 1 - HOLD) cam = cams[k + 1];
+    else cam = between(cams[k], cams[k + 1], ease((f - HOLD) / (1 - 2 * HOLD)));
+    const tx = cam.ax - cam.s * (cam.cx - origin[0]);
+    const ty = cam.ay - cam.s * (cam.cy - origin[1]);
+    world.style.transform = `matrix(${cam.s}, 0, 0, ${cam.s}, ${tx}, ${ty})`;
+    const fade = still() ? (p < 0.5 ? 1 : 0) : Math.max(0, 1 - p / HOLD);
+    hero.style.opacity = String(fade);
+    hero.style.visibility = fade > 0 ? "" : "hidden";
+    hero.style.translate = still() ? "" : `0 ${(-p * span * 0.3).toFixed(1)}px`;
+    const at = Math.round(p);
+    choose(at >= 1 && at < last ? at - 1 : -1);
+  };
+
+  const later = () => {
+    if (queued) return;
+    queued = true;
+    requestAnimationFrame(render);
+  };
+  addEventListener("scroll", later, { passive: true });
+  const sizes = new ResizeObserver(() => {
+    measure();
+    later();
+  });
+  sizes.observe(pin);
+  sizes.observe(hero);
+  document.addEventListener("visibilitychange", () => {
+    if (current < 0) return;
+    if (document.hidden) clips[current].pause();
+    else if (!still()) start(clips[current]);
+  });
+  return { section, host, svg };
+}
diff --git a/site/test/tour.test.ts b/site/test/tour.test.ts
new file mode 100644
index 0000000..558a8b8
--- /dev/null
+++ b/site/test/tour.test.ts
@@ -0,0 +1,44 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { order, type Block } from "../src/iso.ts";
+import { model } from "../src/model.ts";
+import { slab } from "../src/tour.ts";
+
+type Box = Required<Block>;
+const apps = model.slice(1, -1);
+const all = model.flatMap((p) => p.blocks);
+const screens = apps.map((p) => slab(p.name));
+
+const spans = (b: Box) => [
+  [b.x - b.z - b.h, b.x + b.w - b.z],
+  [b.y - b.z - b.h, b.y + b.d - b.z],
+  [b.x - b.y - b.d, b.x + b.w - b.y],
+];
+const overlap = (a: Box, b: Box) => spans(a).every(([lo, hi], i) => lo < spans(b)[i][1] && spans(b)[i][0] < hi);
+const drawn = (list: Box[]) => {
+  const at = order(list);
+  return (b: Box) => at.indexOf(list.indexOf(b));
+};
+
+test("the desk and every screen draw without intersections", () => {
+  const list = [...all, ...screens.flat()];
+  assert.equal(order(list).length, list.length);
+});
+
+test("nothing covers a screen's face, so its clip shows true", () => {
+  for (const [i, p] of apps.entries()) {
+    const rows = screens[i].filter((b) => b.w > 0.2);
+    const list = [...all, ...screens[i]];
+    const rank = drawn(list);
+    for (const row of rows)
+      for (const b of all) assert.ok(!(overlap(row, b) && rank(b) > rank(row)), `${p.name} covered by ${JSON.stringify(b)}`);
+  }
+});
+
+test("screens are sixteen by nine", () => {
+  for (const rows of screens) {
+    const face = rows.filter((b) => b.w > 0.2);
+    const h = face.reduce((s, b) => s + b.h, 0);
+    assert.ok(Math.abs(face[0].w / h - 16 / 9) < 1e-9);
+  }
+});
diff --git a/site/video/web.sh b/site/video/web.sh
new file mode 100755
index 0000000..cfc2604
--- /dev/null
+++ b/site/video/web.sh
@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+# Builds web clips, posters and the launch film.
+set -euo pipefail
+
+here="$(cd "$(dirname "$0")" && pwd)"
+rec="$here/out/rec"
+clips="$here/../public/clips"
+film="$here/../public/film"
+mkdir -p "$clips" "$film"
+
+# name source start end
+cuts=(
+  "doc doc 3.0 10.6"
+  "table table 16.0 23.6"
+  "show show-play 2.6 9.6"
+  "pdf pdf 8.8 16.3"
+  "tree tree 9.5 16.8"
+  "mark mark 5.4 13.4"
+)
+
+fade=0.2
+size="scale=1280:720:flags=lanczos,fps=30,format=yuv420p"
+
+for cut in "${cuts[@]}"; do
+  read -r name src start end <<<"$cut"
+  len=$(echo "$end - $start" | bc)
+  at=$(echo "$len - $fade" | bc)
+  one=$(echo "$start + 0.05" | bc)
+  frames=$(echo "$len * 30 / 1" | bc)
+  # Last 0.2 s fades into the first frame.
+  graph="[0:v]trim=start=$start:end=$end,setpts=PTS-STARTPTS,$size[a];
+[0:v]trim=start=$start:end=$one,setpts=PTS-STARTPTS,$size,trim=end_frame=1,tpad=stop_mode=clone:stop_duration=$fade[b];
+[a][b]xfade=transition=fade:duration=$fade:offset=$at[v]"
+  ffmpeg -v error -y -i "$rec/$src.mp4" -filter_complex "$graph" -map "[v]" -frames:v "$frames" -an \
+    -c:v libx264 -profile:v high -preset slow -crf 24 -pix_fmt yuv420p \
+    -movflags +faststart "$clips/$name.mp4"
+  ffmpeg -v error -y -i "$clips/$name.mp4" -an \
+    -c:v libvpx-vp9 -crf 36 -b:v 0 -row-mt 1 -deadline good -cpu-used 2 \
+    "$clips/$name.webm"
+  ffmpeg -v error -y -i "$clips/$name.mp4" -frames:v 1 -q:v 4 "$clips/$name.jpg"
+done
+
+src="$here/out/ElyOffice-launch.mp4"
+ffmpeg -v error -y -i "$src" -vf "scale=1920:1080:flags=lanczos,format=yuv420p" \
+  -c:v libx264 -profile:v high -preset slow -crf 23 \
+  -c:a aac -b:a 160k -movflags +faststart "$film/ely-office.mp4"
+ffmpeg -v error -y -ss 17 -i "$src" -frames:v 1 -q:v 3 "$film/poster.jpg"
+
+ls -l "$clips" "$film"