motion-launch-videos git:20260927.540ca76A

Immutable. This exact content never changes and is served at /api/v1/blob/c16287395b2788f2.

---
name: motion-launch-videos
description: Make a kinetic-typography launch bumper or brand identity sting, a 6 to 20 second looping video of big animated type, from a short brief (product, message beats, palette, format, duration). Claude writes the film as one self-contained HTML canvas file driven by a pure seek(t), then renders it to MP4 with real subframe motion blur, a verified seamless loop, a preview GIF and a poster. Use it for a launch video, product bumper, promo loop, animated type teaser, logo or identity sting, or a social video announcing a product, made in code rather than edited footage. Not for screen recordings, narrated explainers, talking heads or long product demos.
---

# Motion launch videos

A short, loud, looping film of type: a hook, what the product does, a proof, the domain. The whole film is one HTML file that can draw any moment from the time alone, so it previews in any browser, renders frame-exact, and loops without a seam.

The skill folder is `${CLAUDE_SKILL_DIR}`; the reference files call it `<skill>`. When the skill is loaded as a skill, Claude Code fills that variable in. If it shows up literally or is empty in your shell (you opened this file directly, as a subagent or from a copy), it is the folder that holds this SKILL.md: put that absolute path in every command below, or the commands point at `/scripts/...`.

A film lives in the user's project at `videos/<film>/` (`BRIEF.md`, `DESIGN.md`, `src/film.html`, `fonts/`, the built `<film>.html`, `stills/`, `renders/`).

## Ground rules

- **True claims only.** Every word on screen comes from the product's own live pages and is logged with its URL in `BRIEF.md`. No prices, trial terms or numbers the live site does not show today. A product with no live site (a demo, a fictional or unreleased product) takes its words from the user's brief only, logged as such; see [reference/brief.md](reference/brief.md).
- **Four words a beat, one call to action.**
- **`seek(t)` is pure.** No timers, `Date`, `Math.random`, state or CSS animation; seeded randomness only. Layout is measured once, after the fonts load.
- **One file.** Fonts embedded as base64; nothing loads over the network. The build enforces it.
- **The loop is exact.** Frame 0 is the lockup at rest and equals the last frame: `loopcheck` must report a max diff of 0.
- **Look before you ship.** Numbers pass while frames look wrong; read the stills and the decoded frames.
- **The user decides what leaves the machine.** Get a yes before any commit, push or upload.

## Workflow

0. **Once per machine.** `node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" doctor` checks Node 20+, playwright-core, a Chromium, ffmpeg with libx264, ffprobe, npm and tar, and prints the exact command for anything missing. Usually that is `npm install --prefix "${CLAUDE_SKILL_DIR}" --no-package-lock` (or `npm i -D playwright-core` in the user's project, which survives plugin updates), then the Chromium install line it prints if no Chromium is found. Re-run it until it says `DOCTOR OK`.
1. **Brief intake.** Read the product's live site first, then ask at most one round of questions (message, format, duration, palette), or use the defaults: 1080 x 1080, 12 s, 60 fps, 120 BPM, muted, brand colours from the site's CSS. With no live site, the user's brief is the only source; do not fetch a domain that merely shares the product's name. Fill [templates/BRIEF.md](templates/BRIEF.md) into `videos/<film>/BRIEF.md` with every fact and its source. See [reference/brief.md](reference/brief.md).
2. **Copy pass.** 3 to 5 beats of at most 4 words each (hook, what it does, proof, CTA), lifted from the source's own words, one CTA. Crumbs (small typed lines) are facts too and cite a row. Show the user the beats and proceed unless they object; when nobody can answer (a subagent, a scripted run, a "go"), write them into BRIEF.md and proceed. See [reference/brief.md](reference/brief.md) for beat splits at 8, 10, 12 and 15 s.
3. **Design spec, first pass.** Fill [templates/DESIGN.md](templates/DESIGN.md) into `videos/<film>/DESIGN.md`: canvas, 8 px baseline grid, palette roles with contrast, type roles, then every beat (lines, size rules, springs, stagger, transition, accent) on the tempo grid, and the loop seam. Baselines are a first guess here: the real cap heights come from `layout` in step 4. Read [reference/design-spec.md](reference/design-spec.md) (light films and 16:9 or 9:16 formats are covered there), [reference/kinetic-type.md](reference/kinetic-type.md), [reference/techniques.md](reference/techniques.md) and [reference/springs.md](reference/springs.md).
4. **Build, measure, settle the baselines.** Copy [templates/film.html](templates/film.html) to `videos/<film>/src/film.html` and transcribe DESIGN.md into its `FILM` block (edit nothing below it; the build copies `FILM.title`, the background and the canvas size into the page head). Fetch the fonts, build, and read the measured layout:
   ```bash
   node "${CLAUDE_SKILL_DIR}/scripts/fonts.mjs" videos/<film>
   node "${CLAUDE_SKILL_DIR}/scripts/build.mjs" videos/<film>
   node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" layout videos/<film>    # sizes, cap tops, ink boxes
   ```
   Move each baseline to the grid from the reported cap heights, then write the final numbers into DESIGN.md and FILM together. See [reference/engine.md](reference/engine.md) for every FILM field and [reference/fonts.md](reference/fonts.md).
5. **Pre-pass stills and critique.** `node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" stills videos/<film>` runs the automated critique (glyph coverage from each font's cmap, words per beat, live area, collisions, letter gaps with the `pairs` value that fixes each, orphans, contrast, palette, loop tail, blank frames) and writes stills plus `stills/contact.png`. Read the contact sheet and the full-size stills for cramped type, orphans, contrast and off-palette mixes; fix and repeat until it passes and looks right. See [reference/review.md](reference/review.md).
6. **Render and verify.**
   ```bash
   node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" loopcheck videos/<film>   # every diff must be 0
   node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" render videos/<film>      # MP4, GIF, poster
   node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" verify videos/<film>      # ffprobe facts, tags, decoded pixels
   node "${CLAUDE_SKILL_DIR}/scripts/render.mjs" mp4frames videos/<film>   # decoded review frames + PSNR
   ```
   Then look at `stills/mp4/contact.png` and the full-size decoded frames at each accent, the mask, the pan and the lockup. Report the files, their sizes and the verify, loopcheck and mp4frames lines. See [reference/render.md](reference/render.md) and [reference/motion-blur-loop.md](reference/motion-blur-loop.md).

## Pass criteria

- Display type fits its measure exactly; pairs keep 0.037 em of ink gap; every baseline is on the grid.
- Something moves on every beat; transitions vary (cut, mask wipe, smash-pan); one accent per scene at most.
- Every transition lands on something: no run of blank frames at a cut or at the loop point.
- Misregistration only on landing frames, and two chromatic inks never share a pixel.
- Motion blur on every moving frame, never across a hard cut; fast moves read as streaks, not copies.
- Only palette colours; display type at least 3:1 and crumbs at least 4.5:1 against the background.
- The deliverable MP4 is H.264, yuv420p, BT.709-tagged in the stream, faststart, exactly DUR x FPS frames.

## Known pitfalls

- A blurred `fillText` blurs a whole-canvas layer (about 25 ms at 1080 px). The engine caches blurred glyphs as sprites; keep new blurred drawing going through `fillGlyph`.
- The browser cannot tell you a font lacks a glyph; it falls back silently. Trust the cmap check, not a screenshot.
- Canvas drawing is lazy: timing `seek()` alone measures nothing; time `seek` plus `getImageData`.
- A spring never lands exactly; the engine snaps at `16 / (ζω)`. A custom easing that does not snap breaks the loop.
- `set()` on a visible element is a pop. Only while invisible, at a cut, or inside fast blur.
- Frame 0's subframes wrap to the end of the loop: the tail must be a static copy of t = 0.
- The mask wipe needs something already on screen in the incoming scene, or it reveals an empty frame; a cut needs something that is on screen at once (`enter.pop`), not a fade-in.
- Decode MP4 frames with `accurate_rnd+full_chroma_int` (verify and mp4frames do). swscale's default path reads 1 to 3 levels dark: white as 253, `#0B0B10` as 10,10,13. With the flags, `#0A0A0A` decodes as exactly 10. A background near `#171717` means the range or matrix is wrong.