Engineering Briefing Board 工程简报板

The Ship Decides·40s·Lemo-Opuscarby Lemomo

One real whiteboard wall, filmed: window light on enamel, ghosts of erased marker, frame and tray. Cut-out photographs of real things land on it with weight; tags, magnets, a ruler and stamps are pinned to it; marker ink draws itself in three colours with fixed meanings. The camera rides the lines from fact to fact and only at the end pulls back to show the whole briefing.

The demo: A river needs a bridge; four bridge types are tested on one briefing wall, and the ship that must pass underneath picks the winner.

Engineering decisionsOption comparisonsBriefings & explainers

Style prompt · STYLE.md

One real whiteboard wall, filmed: window light on enamel, ghosts of erased marker, frame and tray. Cut-out photographs of real things land on it with weight; tags, magnets, a ruler and stamps are pinned to it; marker ink draws itself in three colours with fixed meanings. The camera rides the lines from fact to fact and only at the end pulls back to show the whole briefing. References (grammar only): explainers filmed on a map wall; the long pull-back over a wall covered in work; drafting conventions (plan above elevation, dimension lines, hatching). Never copy them or name them in the film.

1. Essence, and what it is not

A physical board in a room: enamel, window falloff, a sliding reflection, ghosts of earlier work, frame and tray.
Real things on it: cut-out photographs of the real objects, a few millimetres off the board, shadowed by one window, parallaxing. They are evidence: never a generated image presented as a real object.
Ink that means something: graphite for names and rules, blue for water and measurement, red only for the decision; rejected ideas erased to ghosts.
One continuous wall: no pages; the camera travels along lines, projections and leaders.
The whole wall, once: every shot is a crop of the final briefing, seen whole only in the last pull-back, as a poster.

Not Whiteboard Explainer (a hand drawing line art on a flat page): the board is a filmed object, subjects are photographs. Not Data Storytelling: comparisons are dimension lines in real units beside real objects. Not a keynote: no headers, centred bullets, page turns.

2. Materials & rendering

Board (z 0): procedural enamel, wiped ghost strokes, smudges, a window falloff, a sliding diagonal reflection; the frame shadows a warm grey wall.
Ink (multiply): flat colour at about 90 %, lighter core, round caps, a wet-tip glint on the stroke being drawn. Lettering: a marker font revealed glyph by glyph with seeded tilt and baseline jitter. Erasing leaves a blurred ghost (about 7 %).
Prints (z ≈ 6–14): photographs cut out at full resolution (a matting model, or a hand polygon / mask), clean edges, one shared grade (lower saturation, a touch warmer, lifted blacks). Thin structure (cables, wires, masts, railings) is measured in the photo and redrawn as clean lines in one colour. Shadow = blurred silhouette along one light vector, softer the higher the object. No frame upsamples a photo: ≥ 1 source px per screen px at its largest, measured; cap the zoom or find a bigger source.
Secondary layer (only where the camera never goes before the end): the photos as pinned prints, a source card, sums on sticky notes, a small sketch. Texture and proof for the final wall, lighter than the main line.
Props (z ≈ 8–26): magnetic tags, magnets, a steel ruler, printed cards, a pitted stamp impression; the tray (z 70) nearest the lens.
Camera: parallax by height, sub-frame motion blur (180° shutter), light grain. Only subtitles are screen-space.

3. Colour logic

Ground: the enamel and its light falloff; the wall around is neutral warm grey.
Ink: graphite = names, rules, facts; blue = water and measurement (dimensions, projection lines, measured numbers); red = the decision (a rejection, the key word of a verdict, the one mark to notice); grey for drafting only (extension lines, hatching).
Red is rare: two or three red marks per frame at most, never on a red object. Full colour belongs to the photographs; props stay neutral; a red magnet is a verdict.

4. Type & subtitles

Marker lettering: a single-weight marker face covering every script the film uses (ours: LXGW Marker Gothic, OFL, subset — re-run when words change). Content 100–160 board px; a verdict 230–400.
Printed labels (tags, cards, stamps): a sturdy sans; credit lines in a monospace. A tag holds one to three words.
Subtitles: a frosted acrylic strip at the bottom centre with a blue marker tick. If the film is bilingual, the film's language sits on top. One line per language: nowrap, measured in the page against a 1,500 px safe width; a long line becomes two cues. Key content stays above the strip (bottom 15 %).
Reading time: subtitles ≥ max(1.8 s, speech + 0.6 s); board text stays fully in frame for CJK ÷ 4.5 + other ÷ 15 + 1.5 s from when it appears. In the final wall, text meant to be read is ≥ 20 px on screen.

5. Motion quality

24 fps on ones; nothing is stepped.
Camera: overlapping eased moves, velocity ∝ u^a (1−u)^b (a, b ≈ 1.5–4), so speed and acceleration never jump; b > a gives inertia. A hand-held breath (≤ 3 px) underneath; shake only on an impact.
Weight: prints are lowered from the camera side, land, bounce and settle as the shadow tightens; magnets clack on to pin them; tags swing; removed magnets pop toward the lens; struck things jolt and spring back. The camera may meet a landing close, briefly, on the object's most telling detail, then pulls out.
Blurred in motion, sharp where words are read. Every 1–2 beats something lands, draws or swings; only silences and judgement holds go still.
Ink draws at the speed of a hand; dimension lines land with an arrowhead tap.
Never: dissolves, scale-pops on text, bouncy UI easing, text fading in by itself.

6. Camera grammar

Move	What it expresses	Can serve
Ride a line (with the pen or a dimension)	measuring; "how far does it go?"	lengths compared; a route; a timeline
Tilt along projection lines	the same quantity in another view	plan → elevation; a total → its parts
Slow push-in, slight Dutch tilt	tension, an approaching problem	a collision; a deadline; an overrun
Pull back and sideways	stepping back to state a rule	a constraint; a turn in the argument
Whip with the line, overshoot, settle	a result that exceeds	a record; an outlier
Rise along a leader line	from evidence to verdict	a conclusion; a recommendation
Staircase framing (each new item with the previous result)	comparison in sequence	rankings; tests; options
Judgement frame: the whole item, the limit and the verdict, held ≥ 2.5 s	a test the viewer can check	pass / fail against a threshold; a budget against a cap
Long pull-back to the whole wall	scale; everything at once	the end of an argument; a summary

Framing: off-centre, cropped, close. The first frame holds a readable subject; the first strong action hits within 0.5 s. Items tested against a limit each get a judgement frame (wider each time if they grow); the verdict lands after the camera settles. Before the reveal: ≤ about 60 % of the board's width, never both side edges, never the reveal's zone. Transitions are moves; no cuts, fades or zoom-to-fit.

7. Sound palette

Room: an air-conditioning bed and traffic through the window, about 20 dB under the voice — audible, not a hiss; silences keep only this.
Foley: felt-tip squeaks scaled to stroke length, nib taps, magnet clacks (a pitch per magnet in a row), suction pops, print landings (board thump, paper slap), a ruler's ring, eraser felt, a stamp's thud.
The subject's own sound arrives early as a J-cut; the first sound after a silence is an impact or the subject's sound.
Music: a small rhythmic ensemble, walking to brisk — bass, a light kit, wooden percussion, low brass stabs for verdicts (or mallets); no piano-and-strings pad. Landings, stamps and arrows sit on the beat. Voice calm, briefing-room confident, about 8–10 dB over the music; −14 LUFS.

8. Native moves

The whole-wall reveal. Design the wall as a poster first (hierarchy, reading path, filling the frame), then plan every shot as a crop of it; keep one zone (secondary layer, verdict, title card) for the reveal alone. Fits: a product roadmap; a household budget.
The subject passes through the answer. The real thing moves through the chosen solution, its sound first. Fits: a parcel along the chosen route; a train over the new viaduct.
Ride the dimension line. A quantity drawn as a real length to one scale; the camera rides the tip. Fits: battery ranges of four cars.
Projection lines. Dashed lines carry an edge from one view to another so two drawings share a scale. Fits: a trail map above its elevation profile.
Magnets as countable things. Units clack on in rhythm, pop off when a rule removes them. Fits: seats in a vote.
Erase to a ghost. A rejected idea wiped but faintly visible. Fits: last year's plan under this year's.
The stamp. A verdict lands with a thud and a jolt. Fits: passed / failed tests.
The physical answer. A real prop laid down as the solution. Fits: one cable instead of five.
Leader to the verdict. An arrow from the deciding number to the conclusion. Fits: the bottleneck in a process.

9. Pitfalls of the medium

Text glimpsed in passing fails the reading time. Fix: words where the camera rests; frame each new item with the last result.
Only close-ups. The viewer never sees the whole object against the limit. Fix: detail → judgement frame → hold → verdict → move on.
Photos that don't belong together. Fix: one grade, one light vector, one viewpoint family.
Thin parts lost or stair-stepped by the matte. Fix: key them against the clean background, redraw clean lines at the measured positions.
Upsampled photos go soft in close-ups. Fix: full-resolution cuts, large sources, a per-frame check.
Lettering in photos (signs, names, logos). Fix: paint out, cut, or choose another photo.
The wall seen too early spends the ending; a sparse or tiny final wall wastes it. Fix: measure every frame's visible share; size the hierarchy for the poster; a quiet secondary layer, no empty middle.

10. Sources, facts, engine

Photos: Wikimedia Commons (read each file page's licence and author), national libraries and archives (e.g. the Library of Congress: check each item's rights statement), agency media pages, Flickr Commons. Fine: CC0, public domain, CC BY (credit it). CC BY-SA, "no known restrictions" (≠ CC0) or other terms: name them to the user and ask first. For the user's own product, site or people, ask for their photos. No licensable photo of a real thing → draw it in marker as a sketch; never a generated image presented as the real object.
Facts: keep a FACTS.md in the project folder (each claim on screen or in the voice, its source URL, the quoted wording, or the measurement method) and deliver it with the film. List every photo in CREDITS with source, author and licence.
Extra packages and packs (beyond setup.sh deps voice music): onnxruntime and the BiRefNet-general matting model (MIT, ~970 MB: https://github.com/danielgatis/rembg/releases/download/v0.0.0/BiRefNet-general-epoch_244.onnx, path in $BIREFNET_ONNX) for cut-outs; fonttools only to subset CJK fonts offline. The agent installs them itself into a private venv in the project folder (demo/kit/tools/kit_env.sh does venv and model), never into $LIB/.venv. Without the model: cut with prep_object.py --poly (hand polygon) or --mask (a mask image).
Engine (copy into the project): demo/kit/board.js (camera, prints, tags, magnets, ruler, cards, stamp, ink, erasing, sceneTexts(t), subCheck(); fields in demo/kit/README.md), demo/kit/batch.mjs (stills), demo/kit/tools/ (cut-outs, line redraws, lettering wipe, prints, fonts), checks in demo/tools/ (camcheck.mjs visible share and judgement frames, rescheck.mjs, subcheck.mjs).

A minimal world (node demo/kit/batch.mjs park.json; fetch_fonts.py park.json first for new characters):

{ "dur": 6, "t": 5.5, "board": { "w": 4000, "h": 2400 }, "hand": 0, "cam": { "x": 1500, "y": 1000, "z": 0.8, "moves": [] },
  "elements": [
    { "type": "tag", "text": "地下车库", "xy": [560, 800], "size": 60, "arrive": { "t": 0.2, "kind": "swing" } },
    { "type": "ink", "kind": "dim", "from": [700, 900], "to": [1300, 900], "color": "blue", "t": 0.6, "d": 0.6 },
    { "type": "ink", "kind": "write", "text": "120 米", "xy": [1360, 940], "size": 100, "color": "blue", "t": 1.2 },
    { "type": "stamp", "text": "首选", "xy": [1500, 700], "size": 110, "rot": -8, "t": 4.2 } ] }

11. Variation space

The agent decides per film: structure, which objects are photographed, plan vs elevation, the wall's reading path, opening, ending, camera path, pacing.

Three structures: one measurement that keeps growing until it breaks a limit; a before/after where the erased first plan stays as a ghost under the second; a checklist stamped item by item as the camera moves down the wall.
Three openings: a stamp on a finished drawing, then back to see why; one number written large, then the line that measures it; a photo dropped onto an empty corner.
Three endings: the wall revealed with the answer circled; back to the opening mark, now corrected; the last tag flipped from a question to an answer, then the pull-back.

How our demo was made (story, shots, score, title card, build): DEMO.md. Read it after your treatment exists.

# Engineering Briefing Board — Style Prompt

> One real whiteboard wall, filmed: window light on enamel, ghosts of erased marker, frame and tray. Cut-out photographs of real things land on it with weight; tags, magnets, a ruler and stamps are pinned to it; marker ink draws itself in three colours with fixed meanings. The camera rides the lines from fact to fact and only at the end pulls back to show the whole briefing.
> References (grammar only): explainers filmed on a map wall; the long pull-back over a wall covered in work; drafting conventions (plan above elevation, dimension lines, hatching). Never copy them or name them in the film.

## 1. Essence, and what it is not

1. **A physical board in a room**: enamel, window falloff, a sliding reflection, ghosts of earlier work, frame and tray.
2. **Real things on it**: cut-out photographs of the real objects, a few millimetres off the board, shadowed by one window, parallaxing. They are evidence: never a generated image presented as a real object.
3. **Ink that means something**: graphite for names and rules, blue for water and measurement, red only for the decision; rejected ideas erased to ghosts.
4. **One continuous wall**: no pages; the camera travels along lines, projections and leaders.
5. **The whole wall, once**: every shot is a crop of the final briefing, seen whole only in the last pull-back, as a poster.

Not **Whiteboard Explainer** (a hand drawing line art on a flat page): the board is a filmed object, subjects are photographs. Not **Data Storytelling**: comparisons are dimension lines in real units beside real objects. Not a keynote: no headers, centred bullets, page turns.

## 2. Materials & rendering

- **Board (z 0)**: procedural enamel, wiped ghost strokes, smudges, a window falloff, a sliding diagonal reflection; the frame shadows a warm grey wall.
- **Ink (multiply)**: flat colour at about 90 %, lighter core, round caps, a wet-tip glint on the stroke being drawn. Lettering: a marker font revealed glyph by glyph with seeded tilt and baseline jitter. Erasing leaves a blurred ghost (about 7 %).
- **Prints (z ≈ 6–14)**: photographs cut out at full resolution (a matting model, or a hand polygon / mask), clean edges, one shared grade (lower saturation, a touch warmer, lifted blacks). Thin structure (cables, wires, masts, railings) is measured in the photo and redrawn as clean lines in one colour. Shadow = blurred silhouette along one light vector, softer the higher the object. **No frame upsamples a photo**: ≥ 1 source px per screen px at its largest, measured; cap the zoom or find a bigger source.
- **Secondary layer** (only where the camera never goes before the end): the photos as pinned prints, a source card, sums on sticky notes, a small sketch. Texture and proof for the final wall, lighter than the main line.
- **Props (z ≈ 8–26)**: magnetic tags, magnets, a steel ruler, printed cards, a pitted stamp impression; the tray (z 70) nearest the lens.
- **Camera**: parallax by height, sub-frame motion blur (180° shutter), light grain. Only subtitles are screen-space.

## 3. Colour logic

- Ground: the enamel and its light falloff; the wall around is neutral warm grey.
- Ink: graphite = names, rules, facts; blue = water and measurement (dimensions, projection lines, measured numbers); red = the decision (a rejection, the key word of a verdict, the one mark to notice); grey for drafting only (extension lines, hatching).
- Red is rare: two or three red marks per frame at most, never on a red object. Full colour belongs to the photographs; props stay neutral; a red magnet is a verdict.

## 4. Type & subtitles

- **Marker lettering**: a single-weight marker face covering every script the film uses (ours: LXGW Marker Gothic, OFL, subset — re-run when words change). Content 100–160 board px; a verdict 230–400.
- **Printed labels** (tags, cards, stamps): a sturdy sans; credit lines in a monospace. A tag holds one to three words.
- **Subtitles**: a frosted acrylic strip at the bottom centre with a blue marker tick. If the film is bilingual, the film's language sits on top. **One line per language**: `nowrap`, measured in the page against a 1,500 px safe width; a long line becomes two cues. Key content stays above the strip (bottom 15 %).
- **Reading time**: subtitles ≥ max(1.8 s, speech + 0.6 s); board text stays fully in frame for CJK ÷ 4.5 + other ÷ 15 + 1.5 s from when it appears. In the final wall, text meant to be read is ≥ 20 px on screen.

## 5. Motion quality

- 24 fps on ones; nothing is stepped.
- Camera: overlapping eased moves, velocity ∝ u^a (1−u)^b (a, b ≈ 1.5–4), so speed and acceleration never jump; b > a gives inertia. A hand-held breath (≤ 3 px) underneath; shake only on an impact.
- Weight: prints are lowered from the camera side, land, bounce and settle as the shadow tightens; magnets clack on to pin them; tags swing; removed magnets pop toward the lens; struck things jolt and spring back. The camera may meet a landing close, briefly, on the object's most telling detail, then pulls out.
- Blurred in motion, sharp where words are read. Every 1–2 beats something lands, draws or swings; only silences and judgement holds go still.
- Ink draws at the speed of a hand; dimension lines land with an arrowhead tap.
- Never: dissolves, scale-pops on text, bouncy UI easing, text fading in by itself.

## 6. Camera grammar

| Move | What it expresses | Can serve |
|---|---|---|
| Ride a line (with the pen or a dimension) | measuring; "how far does it go?" | lengths compared; a route; a timeline |
| Tilt along projection lines | the same quantity in another view | plan → elevation; a total → its parts |
| Slow push-in, slight Dutch tilt | tension, an approaching problem | a collision; a deadline; an overrun |
| Pull back and sideways | stepping back to state a rule | a constraint; a turn in the argument |
| Whip with the line, overshoot, settle | a result that exceeds | a record; an outlier |
| Rise along a leader line | from evidence to verdict | a conclusion; a recommendation |
| Staircase framing (each new item with the previous result) | comparison in sequence | rankings; tests; options |
| Judgement frame: the whole item, the limit and the verdict, held ≥ 2.5 s | a test the viewer can check | pass / fail against a threshold; a budget against a cap |
| Long pull-back to the whole wall | scale; everything at once | the end of an argument; a summary |

## 7. Sound palette

- Room: an air-conditioning bed and traffic through the window, about 20 dB under the voice — audible, not a hiss; silences keep only this.
- Foley: felt-tip squeaks scaled to stroke length, nib taps, magnet clacks (a pitch per magnet in a row), suction pops, print landings (board thump, paper slap), a ruler's ring, eraser felt, a stamp's thud.
- The subject's own sound arrives early as a J-cut; the first sound after a silence is an impact or the subject's sound.
- Music: a small rhythmic ensemble, walking to brisk — bass, a light kit, wooden percussion, low brass stabs for verdicts (or mallets); no piano-and-strings pad. Landings, stamps and arrows sit on the beat. Voice calm, briefing-room confident, about 8–10 dB over the music; −14 LUFS.

## 8. Native moves

- **The whole-wall reveal.** Design the wall as a poster first (hierarchy, reading path, filling the frame), then plan every shot as a crop of it; keep one zone (secondary layer, verdict, title card) for the reveal alone. *Fits:* a product roadmap; a household budget.
- **The subject passes through the answer.** The real thing moves through the chosen solution, its sound first. *Fits:* a parcel along the chosen route; a train over the new viaduct.
- **Ride the dimension line.** A quantity drawn as a real length to one scale; the camera rides the tip. *Fits:* battery ranges of four cars.
- **Projection lines.** Dashed lines carry an edge from one view to another so two drawings share a scale. *Fits:* a trail map above its elevation profile.
- **Magnets as countable things.** Units clack on in rhythm, pop off when a rule removes them. *Fits:* seats in a vote.
- **Erase to a ghost.** A rejected idea wiped but faintly visible. *Fits:* last year's plan under this year's.
- **The stamp.** A verdict lands with a thud and a jolt. *Fits:* passed / failed tests.
- **The physical answer.** A real prop laid down as the solution. *Fits:* one cable instead of five.
- **Leader to the verdict.** An arrow from the deciding number to the conclusion. *Fits:* the bottleneck in a process.

## 9. Pitfalls of the medium

- **Text glimpsed in passing** fails the reading time. Fix: words where the camera rests; frame each new item with the last result.
- **Only close-ups.** The viewer never sees the whole object against the limit. Fix: detail → judgement frame → hold → verdict → move on.
- **Photos that don't belong together.** Fix: one grade, one light vector, one viewpoint family.
- **Thin parts lost or stair-stepped** by the matte. Fix: key them against the clean background, redraw clean lines at the measured positions.
- **Upsampled photos** go soft in close-ups. Fix: full-resolution cuts, large sources, a per-frame check.
- **Lettering in photos** (signs, names, logos). Fix: paint out, cut, or choose another photo.
- **The wall seen too early** spends the ending; **a sparse or tiny final wall** wastes it. Fix: measure every frame's visible share; size the hierarchy for the poster; a quiet secondary layer, no empty middle.

## 10. Sources, facts, engine

- **Photos**: Wikimedia Commons (read each file page's licence and author), national libraries and archives (e.g. the Library of Congress: check each item's rights statement), agency media pages, Flickr Commons. Fine: CC0, public domain, CC BY (credit it). CC BY-SA, "no known restrictions" (≠ CC0) or other terms: name them to the user and ask first. For the user's own product, site or people, ask for their photos. No licensable photo of a real thing → draw it in marker as a sketch; never a generated image presented as the real object.
- **Facts**: keep a `FACTS.md` in the project folder (each claim on screen or in the voice, its source URL, the quoted wording, or the measurement method) and deliver it with the film. List every photo in `CREDITS` with source, author and licence.
- **Extra packages and packs** (beyond `setup.sh deps voice music`): `onnxruntime` and the BiRefNet-general matting model (MIT, ~970 MB: https://github.com/danielgatis/rembg/releases/download/v0.0.0/BiRefNet-general-epoch_244.onnx, path in `$BIREFNET_ONNX`) for cut-outs; `fonttools` only to subset CJK fonts offline. The agent installs them itself into a private venv in the project folder (`demo/kit/tools/kit_env.sh` does venv and model), never into `$LIB/.venv`. Without the model: cut with `prep_object.py --poly` (hand polygon) or `--mask` (a mask image).
- **Engine** (copy into the project): `demo/kit/board.js` (camera, prints, tags, magnets, ruler, cards, stamp, ink, erasing, `sceneTexts(t)`, `subCheck()`; fields in `demo/kit/README.md`), `demo/kit/batch.mjs` (stills), `demo/kit/tools/` (cut-outs, line redraws, lettering wipe, prints, fonts), checks in `demo/tools/` (`camcheck.mjs` visible share and judgement frames, `rescheck.mjs`, `subcheck.mjs`).

A minimal world (`node demo/kit/batch.mjs park.json`; `fetch_fonts.py park.json` first for new characters):

```json
{ "dur": 6, "t": 5.5, "board": { "w": 4000, "h": 2400 }, "hand": 0, "cam": { "x": 1500, "y": 1000, "z": 0.8, "moves": [] },
  "elements": [
    { "type": "tag", "text": "地下车库", "xy": [560, 800], "size": 60, "arrive": { "t": 0.2, "kind": "swing" } },
    { "type": "ink", "kind": "dim", "from": [700, 900], "to": [1300, 900], "color": "blue", "t": 0.6, "d": 0.6 },
    { "type": "ink", "kind": "write", "text": "120 米", "xy": [1360, 940], "size": 100, "color": "blue", "t": 1.2 },
    { "type": "stamp", "text": "首选", "xy": [1500, 700], "size": 110, "rot": -8, "t": 4.2 } ] }
```

## 11. Variation space

The agent decides per film: structure, which objects are photographed, plan vs elevation, the wall's reading path, opening, ending, camera path, pacing.

- **Three structures:** one measurement that keeps growing until it breaks a limit; a before/after where the erased first plan stays as a ghost under the second; a checklist stamped item by item as the camera moves down the wall.
- **Three openings:** a stamp on a finished drawing, then back to see why; one number written large, then the line that measures it; a photo dropped onto an empty corner.
- **Three endings:** the wall revealed with the answer circled; back to the opening mark, now corrected; the last tag flipped from a question to an answer, then the pull-back.

---

How our demo was made (story, shots, score, title card, build): [DEMO.md](DEMO.md). Read it after your treatment exists.

Director's notes for the demo film

One example among many. Don't reuse its story, arc, shots, props or timings.

Demo: The Ship Decides (船说了算, 40.0 s) · briefing-board.mp4 · source in demo/

A river 1,000 m wide needs a bridge. The first instinct, piers all the way across, is stamped out the moment a container ship sails into one of them. The new rule: no piers in the channel, one span. Four bridge types are tested against the river's width, drawn to one scale. The river set the question; the ship sets the span.

Story & structure

Shape: an elimination that turns early. Hook (0–1 s): the river's width snaps across in the first quarter-second. Setup (1–8 s): "1,000 米", a pier-by-pier beam crossing. Turn (8 s): after a second of near-silence the ship touches the centre pier and a red stamp lands. Development (11–27 s): the rule is written, the piers pop off, a steel ruler is laid bank to bank; dashed projection lines carry the banks down into an elevation "test bench" where four photographed bridges land one after another, each met close by the camera as it lands, then judged in a held frame that shows the whole bridge, the two bank lines (the 1,000 m "door"), its dimension line drawn to its record main span, and the verdict landing after the camera has settled. Each judgement frame is wider than the last, so the widening is the rhythm: the cable-stayed line crawls just past the far bank, the suspension line rockets past it and throws the camera. Ending (32.8–40 s): down at the waterline a side-view container ship comes out from behind the far tower and sails under the suspension span; half a second of room tone; then the only pull-back, starting from the ship, to the whole wall, where the verdict "船决定跨度" is written beside the results. The final frame is the poster.

Why it fits the style: one continuous wall holds a plan view (top-down ship, river, crossing) above an elevation view (side-on bridges) with projection lines between them — a real drafting convention, so a top-down ship and side-on bridges share one board without breaking geometry. The same ship appears in both views: the problem in plan, the answer in elevation. Native moves spent: magnets as countable things, the stamp, erase to a ghost, the physical answer (the ruler), projection lines, ride the dimension line (four times), the subject passes through the answer, leader to the verdict, and the whole-wall reveal as the signature shot.

Shots

One continuous camera, no cuts. Times in seconds; zoom 1 = 1,920 board px across.

#	Time	Shot	Camera	Native move / note
1	0.0–1.2	ECU on the left bank, the dimension arrow already leaving it	z 2.6, roll −3°; whips right with the line as it snaps across (0.25), overshoots, settles (z 1.32)	the hook: line, brass hit and kick in the first 0.25 s
2	1.2–2.9	MCU on "1,000 米" being written	push in (z 1.42), roll +1°
3	2.9–5.5	MS of the crossing	tilt down as the deck draws, then track right along seven pier magnets (eighths)	magnets as countable things
4	5.5–8.0	MS → CU up the channel	tilt up as the horn sounds (J-cut), then a slow push to z 2.05 with a −1.6° Dutch tilt	silence 7.0–8.0
5	8.0–10.7	CU on the bow, the pier and the stamp → the whole ship	impact shake, then a pull back along the hull (z 1.42)	the stamp; the centre pier jolts
6	10.75–14.4	MS: the rule; the river edge	pull back right (z 1.0), ride the marker as the rule is written, drift back as the piers pop	erase to a ghost; the ruler drops at 14.0
7	14.4–15.25	ECU: the beam's pier foot as the print lands (15.0)	tilt down the dashed projection lines into it (z 2.05)	projection lines; two magnets pin each print
8	15.25–18.45	Judgement: beam — whole bridge, both bank lines, 330 m line, tag, number	pull out (z 1.09), hold 15.85–18.45 (2.6 s) with a slow push	line 15.875–16.25; red strike and dashed shortfall at 17.125
9	18.45–19.25	CU: the arch rib and hangers as it lands (19.0)	crane down (z 1.6)
10	19.25–22.45	Judgement: arch, with the beam's result above	pull out (z 0.99), hold 19.85–22.45 (2.6 s)	line 19.875–20.25; strike 21.125
11	22.45–23.4	CU: the pylon top and its fan as it lands (23.125)	crane down (z 1.8)
12	23.4–28.2	Judgement: cable-stayed, with the arch's result above	pull out (z 0.81), hold 24.08–28.2 (4.1 s)	the line crawls 24.125–25.625 just past the right bank line; "勉强" at 26.0
13	28.2–29.1	CU: the near tower and its long hangers as the heaviest print lands (28.875)	crane down (z 1.38, capped by rescheck)
14	29.1–32.8	Judgement: suspension, with the cable-stayed result above	pull out (z 0.60), hold 29.83–32.83 (3.0 s); thrown right as the line passes the bank (30.175), settles back	the line rockets 29.875–30.375; ring 31.25; the horn (32.0) brings the side-view ship in at the right edge
15	32.8–35.75	CU at the waterline: the far tower, hangers, the side-view ship	down to the water (z 1.42), then pan left with the ship under the main span	the subject passes through the answer; silence 35.25–35.75
16	35.75–37.8	the whole wall	the only pull-back, from the ship (z 1.42 → 0.2795, 2.05 s)	signature shot: both side edges first in frame at 37.17 s; leader (36.7) and verdict (36.875–37.875) drawn during it
17	38.15–40.0	the whole wall	a slow push (×1.025) that keeps the wall whole; a cloud shadow crosses the wall	the end card is part of the wall

Judgement frames widen 1,768 → 1,945 → 2,361 → 3,205 board px (28 % → 50 % of the wall's width). tools/camcheck.mjs checks each one: the whole box (print, both bank lines, dimension line, labels, verdict) stays in frame and above the subtitle strip for the whole hold. Before 35.75 s the camera never shows more than 51.4 % of the board's width, never both side edges and none of the right zone (prints, cards, notes, verdict, end card). tools/rescheck.mjs checks that no frame shows any photo at less than one source pixel per screen pixel (lowest: the stretched suspension span, 1.03, at its landing).

Score structure

120 BPM, 4/4, D minor → D major at the reveal. Instruments: electric bass (eighth-note figure), MuldjordKit kick/snare/hats, claves, shaker, low brass stabs (trombone, tuba, horn), timpani, gran cassa, crash, tubular bells, glockenspiel, vibraphone. No piano, no string pad.
Arc: the hook (Dm brass stab, low tom, kick with the snapping line at 0.25) → groove A → low-pass dive → silence 7.0–8.0 → stamp: Dm brass stab + timpani + gran cassa → half time (held D, low toms) → groove A rebuilt under the rule → groove B (kit) under the test bench, one brass stab per landing in the bar's chord, a sour trombone blat (D + E♭) per strike → the cable crawl: bass climbs chromatically in eighths G1 → G2 with a shaker swell → "just enough": two horn notes → snare sixteenths into the suspension's line (A, dominant, on the landing) → the line lands: crash + a bright B♭ chord (VI) → vibraphone pair on the ring → bass whole notes and soft trombone fifths under the last line and the ship → silence 35.25–35.75 → the reveal: the ship's horn tuned to D (root and fifth) with a D-major brass chord, timpani and tubular bells → the verdict is written to a horn line A–F♯–E–D–A → glockenspiel D–F♯–A–D while the wall settles.
Hits: every landing, pin, stamp, arrow, strike and tag sits on the 16th-note grid (tools/cuecheck.py: 27/27 at 0 ms).
Foley (procedural, audio/mix.py): felt-tip squeaks scaled to stroke length, nib taps, magnet clacks pitched per pier, two pin clacks after every landing, suction pops, print landings (board thump + paper slap, heavier for the suspension), the steel ruler's ring, eraser felt, rubber stamp, ship horn (far and near), diesel rumble, water lapping, whooshes, room tone with distant traffic.
J-cuts: the horn at 5.75 before the top-down ship is seen; the horn at 32.0 before the side-view ship comes out from behind the tower. L-cuts: the eraser over the move into the bench; the reveal horn over the whole pull-back.
Mix: music about 9 dB under the voice and ducked; foley ducked under speech; room tone (air conditioning on the right, traffic through the window on the left) about 20 dB under the voice and never ducked; silences gated to that room tone; −14 LUFS integrated.
Voice: Kokoro af_heart, nine lines; numbers spelled out for TTS and written as digits in the subtitles.

Palette & props

Board 6,400 × 3,600 board px (16:9, so the final pull-back fills the frame); enamel #F3F1EB; wall #8F8B83; ink graphite #23272E, blue #1F4FC8, red #D33A21, water hatching #5F86DA, drafting grey #6C727B.
Plan view (top left): river 1,240 px = 1,000 m between two blue banks with grey ground hatching; "1,000 米" above; crossing with seven graphite magnets; the top-down ship scaled to 500 px (about true scale); stamp "否决" (Noto Sans SC 900, pitted red). Rule "新规矩" red with an underline, "航道不立墩" graphite (LXGW Marker Gothic). The ruler: brushed steel with engraved graduations, a magnet at each end.
Elevation (left two-thirds): projection lines dashed blue; four rows scaled so each main span is its record length at 1.24 px per metre (330, 600, 1,208, 2,023 m); each print pinned by two magnets; under each arrow end a label block: a name tag (Noto Sans SC 700, 78 px) and the number in blue marker (100 px), the tag placed by the number's measured width so they never touch. The side-view ship is 340 px long (about true scale) on a hand-drawn waterline. The cable-stayed bridge is a mirrored composite of a single-pylon photo and the suspension bridge's main span is stretched ×1.7 (see demo/CREDITS).
Right third (never in shot before the reveal): four photo prints with magnets (suspension, cable-stayed, arch, and the side-view ship whose lettering was wiped), a source card ("数据来源"), two sticky notes with the sums (1,208 − 1,000 = 208; 2,023 ÷ 1,000 ≈ 2), a small navigation-clearance sketch without numbers, the verdict "船决定跨度" (400 px, "船" red) at the right middle with a leader from the circled 2,023, and the end card.
Subtitles: frosted strip, Chinese Noto Sans SC 500 42 px over English Archivo 500 29 px, blue tick at left; every cue measured on one line per language (tools/subcheck.mjs).

Title card

A printed card pinned at the bottom right of the wall from the start, seen only in the reveal: "船说了算", a red rule, "ENGINEERING / BRIEFING BOARD", "工程简报板", "LemoLab × Claude Opus 5.5". It is part of the final wall (the poster) and is on screen for the last three seconds. The "LemoLab × Claude Opus 5.5" sign-off belongs to this library's demo only; a user's film carries no LemoLab credit and no copy of this card.

Build notes

demo/
  index.html            the page: fonts, setScene / render / TEXTS / SUBCHECK / RESCHECK
  kit/board.js          the renderer (style engine)            kit/batch.mjs   stills from scene JSON
  kit/objects/          cut-outs + meta (anchors L/R for bridges, bow/stern for the ships)
  kit/tools/            prep_object.py, sky_key.py, mirror_span.py, stretch_span.py, redraw_stays.py,
                        redraw_suspension.py, repair_hangers.py, clean_lettering.py, ship_anchors.py,
                        make_print.py, rebuild_objects.sh; fetch_fonts.py, fetch_sources.py, kit_env.sh
  scenes/_gen_film.py   the film as data → scenes/film.json, audio/cues.json
  audio/lines.json      narration (Kokoro)          audio/mix.py   score, foley, voice, mix
  tools/                camcheck.mjs + camplot.py, rescheck.mjs, subcheck.mjs, cuecheck.py, rhythm_report.py, final_asr.py
  sources/              candidates/candidates.json (every photo looked at: URL, author, licence, evidence;
                        the six used ones with sha256); photos, masks and derived/ are downloaded or rebuilt

sh demo/build.sh (library set up with setup.sh deps voice music): fetches what git does not hold — fonts from Google Fonts (fetch_fonts.py: Archivo and IBM Plex Mono from github.com/google/fonts, the CJK subsets through the CSS API), the six photos from Commons (fetch_sources.py, ~470 MB), a private demo/.venv with onnxruntime and the BiRefNet model (kit_env.sh, ~970 MB unless cached), the voice model and the freepats / vsco2ce / vcsl samples — and cuts the objects again (rebuild_objects.sh); then speech check → scene → cue check → reading check → camera check (incl. judgement frames) → resolution check → events → render (960 frames, 5 workers) → mix → subtitles (+ one-line check) → mux (−14 LUFS, grain 1) → poster and styleframe → rhythm report → speech check on the final mix → camera plot.
Objects: sh demo/kit/tools/rebuild_objects.sh recreates every cut-out from the photos at their own resolution (BiRefNet masks are cached in sources/masks/; a recomputed mask can differ by a pixel or two from ours).
Stills and thumbnails: a scene JSON that extends scenes/film.json with its own cam and t, rendered by node demo/kit/batch.mjs.

Bridge-specific choices: each landing is met close on a pylon top, an arch rib, the hangers or a pier's foot; stays, main cables and hangers are redrawn as clean lines at the positions measured in the photos. Pitfalls tied to this demo: the first cut rode each dimension line close and never showed the cable-stayed or suspension bridge whole; viewers lost what was being tested ("too fast"). The fix was the judgement frame per bridge, held, widening each time, with the voice and the verdict inside the hold. Text first glimpsed during a move failed the reading check, so every label block is pinned where the camera rests and each new row is framed with the previous row's result. The first cut-outs were downscaled and the close-ups upsampled them (a blocky ship); every object is now cut at full resolution and rescheck.mjs caps each zoom. Keyed stays turned into stair-steps and arch hangers vanished against the hills; stays and suspension cables are now measured and redrawn, the arch hangers continued to the deck. Name tags at a fixed offset overlapped the wider numbers; they are placed from the number's measured advance width. The stretched suspension photo allows z 1.38 at most, so its landing close-up is on the near tower, which is not stretched. The photographed suspension bridge has the proportions of a 500 m span; scaled uniformly to 2,023 m its towers would be far too tall, so only the main span is stretched. A road sign, a water-level gauge, a ship's name and container logos were removed (lettering). The pier clacks masked "piers" in the voice; they were lowered.