diff --git a/site/public/film/ely-office.mp4 b/site/public/film/ely-office.mp4
index 266225a..882cc2f 100644
Binary files a/site/public/film/ely-office.mp4 and b/site/public/film/ely-office.mp4 differ
diff --git a/site/test/film.test.ts b/site/test/film.test.ts
new file mode 100644
index 0000000..0267a85
--- /dev/null
+++ b/site/test/film.test.ts
@@ -0,0 +1,29 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { BEAT, bar } from "../video/type/draw.js";
+import { nameCubes } from "../video/type/scenes.js";
+import { moment } from "../video/scenes/timeline.ts";
+import { recording, slabs } from "../video/scenes/turn.ts";
+import { grown } from "../video/scenes/parts.ts";
+import recs from "../video/montage/recs.json" with { type: "json" };
+
+const APPS = ["Doc", "Table", "Show", "PDF", "Tree", "Mark"];
+
+test("each app's name clears before its screen flattens", () => {
+  APPS.forEach((name, i) => {
+    const b = 9 + 4 * i;
+    // The screen flattens on the bar's last beat.
+    const flat = bar(b) + 3 * BEAT;
+    assert.ok(nameCubes(`Ely${name}`, b, flat - BEAT).some((c) => c.a > 0), `Ely${name} shows first`);
+    assert.ok(nameCubes(`Ely${name}`, b, flat).every((c) => c.a === 0), `Ely${name} is gone`);
+  });
+});
+
+test("leaving screens keep their place and play as they go", () => {
+  assert.deepEqual(slabs, recs.apps.map(({ app }) => grown(app)), "the montage's own screens");
+  for (let f = 2186; f < 2215; f++) {
+    const shown = moment(f / 30).pieces.filter(({ box, land }) => slabs.includes(box) && land > 0);
+    assert.ok(shown.every(({ box, land }) => recording(box, land, f)), `frame ${f}`);
+    if (f === 2186) assert.equal(shown.length, 6, "all six cross the cut");
+  }
+});
diff --git a/site/video/montage/scene.ts b/site/video/montage/scene.ts
index 9a39e21..f97306e 100644
--- a/site/video/montage/scene.ts
+++ b/site/video/montage/scene.ts
@@ -1,6 +1,6 @@
 // Montage: six screens on the turning model, in WebGL.
 import { model } from "../../src/model.ts";
-import { type Box, SCREEN, screens } from "../scenes/parts.ts";
+import { type Box, grown, screens } from "../scenes/parts.ts";
 import { BEAT, glide, toward } from "../scenes/time.ts";
 import recs from "./recs.json";
 
@@ -12,18 +12,9 @@ export const FIRST = recs.first;
 export const COUNT = 129;
 const TURN: [number, number] = [128, 136];
 const PIVOT = [8, 5.5];
-const GROW = 1.5;
-const TOP = model[0].blocks[0].h;
 const apps = recs.apps;
 
-/** A screen grown about its bottom centre; Show on its base. */
-function slab(app: string): Box {
-  if (app === "ElyShow") return { x: 8.6, y: 2, z: TOP + 0.25, w: 4.8, d: 0.08, h: 2.7, tone: SCREEN };
-  const b = screens[app];
-  const w = b.w * GROW;
-  return { ...b, x: b.x + (b.w - w) / 2, w, h: b.h * GROW };
-}
-const slabs = apps.map((a) => slab(a.app));
+const slabs = apps.map((a) => grown(a.app));
 const ground = model.flatMap((p) => p.blocks).filter((b) => b !== screens.ElyShow);
 
 type Rgb = [number, number, number];
diff --git a/site/video/scenes/page.ts b/site/video/scenes/page.ts
index 9e6c8dc..872d993 100644
--- a/site/video/scenes/page.ts
+++ b/site/video/scenes/page.ts
@@ -5,8 +5,7 @@ import { ACCENT, model } from "../../src/model.ts";
 import { type Box, DESK, PAPER, SCREEN, SHEET, lamp, props, screens, tiles } from "./parts.ts";
 import { BAR, BEAT, glide, toward } from "./time.ts";
 import { DESK_END, type Moment, SEED, TURN, moment } from "./timeline.ts";
-import { film, montage, slabs, turnedBlock, turnedOrder } from "./turn.ts";
-import recs from "../montage/recs.json";
+import { film, montage, recording, turnedBlock, turnedOrder } from "./turn.ts";
 import { view } from "../opening/plan.ts";
 
 export const WIDTH = 1920;
@@ -167,7 +166,7 @@ const svg = document.querySelector<SVGSVGElement>("#frame");
 const world = document.querySelector<SVGGElement>("#world");
 if (!svg || !world) throw new Error("index.html lacks #frame or #world");
 
-/** Draws the moment; slabs carry the montage recordings at frame `f`. */
+/** Draws the moment; leaving slabs carry their recordings. */
 function draw(m: Moment, cam: Camera, f: number): Promise<void>[] {
   const page = mix(PAGE[0], PAGE[1], m.dark);
   document.body.style.background = page;
@@ -177,10 +176,9 @@ function draw(m: Moment, cam: Camera, f: number): Promise<void>[] {
   const groups = m.pieces.map(({ box, land, dark }) => {
     const toned = { ...box, tone: tone(box.tone, dark) };
     const g = m.angle ? turnedBlock(toned, m.angle) : block(toned);
-    const slab = slabs.indexOf(box);
-    if (slab >= 0 && land > 0) {
-      const index = String(f - recs.first + 1).padStart(5, "0");
-      const { el, ready } = film(box, m.angle, `rec/${recs.apps[slab].rec}/${index}.jpg`);
+    const href = recording(box, land, f);
+    if (href) {
+      const { el, ready } = film(box, m.angle, href);
       g.append(el);
       loads.push(ready);
     }
diff --git a/site/video/scenes/parts.ts b/site/video/scenes/parts.ts
index c137bda..76c4d48 100644
--- a/site/video/scenes/parts.ts
+++ b/site/video/scenes/parts.ts
@@ -163,3 +163,11 @@ export const props: Prop[] = [
     ]),
   },
 ];
+
+/** A screen grown about its bottom centre; Show on its base. */
+export function grown(app: string): Box {
+  if (app === "ElyShow") return { x: 8.6, y: 2, z: model[0].blocks[0].h + 0.25, w: 4.8, d: 0.08, h: 2.7, tone: SCREEN };
+  const b = screens[app];
+  const w = b.w * 1.5;
+  return { ...b, x: b.x + (b.w - w) / 2, w, h: b.h * 1.5 };
+}
diff --git a/site/video/scenes/turn.ts b/site/video/scenes/turn.ts
index c49c231..2337cd1 100644
--- a/site/video/scenes/turn.ts
+++ b/site/video/scenes/turn.ts
@@ -1,13 +1,12 @@
 // The model turned about the desk centre, as the montage draws it.
 import { project } from "../../src/iso.ts";
 import { model } from "../../src/model.ts";
-import recs from "../montage/recs.json";
-import { type Box, SCREEN, screens } from "./parts.ts";
+import recs from "../montage/recs.json" with { type: "json" };
+import { type Box, grown } from "./parts.ts";
 
 const SVG = "http://www.w3.org/2000/svg";
 export const PIVOT = [8, 5.5];
 const COS = Math.cos(Math.PI / 6);
-const TOP = model[0].blocks[0].h;
 
 /** A world point turned by `a`, then projected. */
 export function turned(a: number, x: number, y: number, z: number): [number, number] {
@@ -16,12 +15,14 @@ export function turned(a: number, x: number, y: number, z: number): [number, num
 }
 
 /** The montage's grown screens, which leave in bar 35. */
-export const slabs: Box[] = recs.apps.map(({ app }) => {
-  if (app === "ElyShow") return { x: 8.6, y: 2, z: TOP + 0.25, w: 4.8, d: 0.08, h: 2.7, tone: SCREEN };
-  // The montage drew Tree's screen at its old depth.
-  const b = app === "ElyTree" ? { ...screens[app], y: 7.9 } : screens[app];
-  return { ...b, x: b.x - b.w / 4, w: b.w * 1.5, h: b.h * 1.5 };
-});
+export const slabs: Box[] = recs.apps.map(({ app }) => grown(app));
+
+/** The recording a leaving slab plays at frame `f`, if any. */
+export function recording(box: Box, land: number, f: number): string | null {
+  const slab = slabs.indexOf(box);
+  if (slab < 0 || land <= 0) return null;
+  return `rec/${recs.apps[slab].rec}/${String(f - recs.first + 1).padStart(5, "0")}.jpg`;
+}
 
 /** A slab's recording frame, pinned affinely on its +y face. */
 export function film(b: Box, a: number, href: string): { el: SVGImageElement; ready: Promise<void> } {
diff --git a/site/video/type/scenes.js b/site/video/type/scenes.js
index 663ef48..d9ffc74 100644
--- a/site/video/type/scenes.js
+++ b/site/video/type/scenes.js
@@ -118,21 +118,25 @@ function title(ctx, t) {
   text(ctx, { s: "六个桌面应用", x: left, y: y + 46, size: 28, color: SOFT, a, align: "left", track: 2 });
 }
 
+/** App `name`'s letter cubes at `t` in its bar `b`. */
+export function nameCubes(name, b, t) {
+  const t0 = bar(b);
+  const list = word(name, () => INK);
+  const build = slots(list, 8);
+  const out = slots(list, 4, 0);
+  return list.flatMap((c, i) => {
+    const at = arrive(t, t0 + (build[i] + 1) * SIX);
+    if (!at) return [];
+    const gone = lift(t, t0 + (9 + out[i]) * SIX, LAND);
+    return [box(c, at.dz + gone.dz, at.a * gone.a)];
+  });
+}
+
 /** An app's first bar: its name builds at left. */
 function app(name, b) {
   return (ctx, t) => {
-    const t0 = bar(b);
-    const list = word(name, () => INK);
-    const build = slots(list, 8);
-    const out = slots(list, 4, 0);
-    const v = place(list, 16, { left: 112, cy: 800 });
-    const boxes = list.flatMap((c, i) => {
-      const at = arrive(t, t0 + (build[i] + 1) * SIX);
-      if (!at) return [];
-      const gone = lift(t, t0 + (9 + out[i]) * SIX, LAND);
-      return [box(c, at.dz + gone.dz, at.a * gone.a)];
-    });
-    cubes(ctx, v, boxes);
+    const v = place(word(name, () => INK), 16, { left: 112, cy: 800 });
+    cubes(ctx, v, nameCubes(name, b, t));
   };
 }