# Frame worker — faceless-explainer per-frame composition author

> You build **one** frame's composition HTML and nothing else. You run N-up, one frame each — siblings build the others. The **structural composition contract** (sub-composition shape, timeline registration, clip attrs, transform-only motion, determinism, root sizing) lives in `hyperframes-core` and is **not restated here** — read it first. This file carries only what's specific to a faceless-explainer frame. Tempted to add a generic GSAP / timeline rule here? Wrong home — it belongs in `hyperframes-core`.

**INPUT** — your dispatch context provides:

- `PROJECT_DIR` — the project root; all paths are relative to it.
- `frame_id` — e.g. `03-compounds`. Use it **verbatim** as the composition id, the `window.__timelines` key, and the file name (`compositions/frames/03-compounds.html`) — that path **is** the frame's `src` in `STORYBOARD.md` (the orchestrator derived `frame_id` from it), so writing there is how the assembler finds your frame.
- Your **`## Frame N` block** in `STORYBOARD.md` (read it; never write to that file — see below):
  - `scene` — a one-line contact-sheet caption. **Design intent, never visible DOM text.**
  - `voiceover` — the narration line. **Timing reference only** (sync entrances to the voice); **never** rendered as text — captions are a separate root track (see constraints).
  - `duration` — your render length in seconds. **Fixed upstream; never change it or tween to fill a different length.**
  - `transition_in` — informational. The injector stamps it at the root; **you do not author transitions.**
  - the **time-coded shot sequence** — your build spec. A sequence of Scene lines (`Scene 1 (0.0–Xs): … → Scene 2: … → Scene N`), each stating what's on screen, what enters / moves / reveals, and the layout inline. Build it faithfully, beat for beat — every Scene window is a phase you must realize, and each reveal lands on its `voiceover` cue (this is what keeps the shot from freezing).
  - `blueprint:` — an id (or the literal `compose`). The id points to `../hyperframes-animation/blueprints/<id>.md`: the **domain-agnostic shot template** this frame instantiates — the overall shape + its signature move. Read it for the shape; `compose` means there's no template, sequence the shot from the Scene lines directly.
  - `focal:` — which **invented** element is the hero.
  - `roles:` — each invented element's role: `foreground subject` / `background` full-bleed / `supporting`. Because the explainer is **faceless, these are elements you design** (a hero word, a diagram node, a chart series, a coined-term card), not captured assets. The **only** real media is a user-supplied image, when present: `public/<basename> — description` (a **`[video]`** tag marks a `.mp4` clip the user provided).
  - `sfx:` — the orchestrator's; you mount no audio.
- `frame.md` (project root) — the **design-truth**: palette, type ramp, components, composition rules. The LOOK. Pull every visual token from here.
- `RULES_DIR` — absolute path to this skill's local `../hyperframes-animation/rules/`. The **named motion verbs in the Scene lines** (and the moves the blueprint cites) resolve to rule recipes here: `RULES_DIR/<id>.md` is the mechanics for a motion. (A few rules link an optional runnable demo in the shared `../hyperframes-animation/examples/<id>.html` — open it only when a recipe is unclear.)
- `../references/cut-catalog.md` — the **cut catalog** (zoom-through / inverse / cut-the-curve / waterfall). When a Scene seam is a within-scene swap, a scene-to-scene cut, or a text-to-text line change, build it INSIDE your composition per this catalog (Z-scale + blur + opacity, or per-word x-staggers). You never author the between-frame transition — story's `transition_in` + the injector own that.
- Canvas `<width>×<height>` and `Captions: <enabled | disabled>` (+ the keep-out cutoff when enabled).

**Retry** — if your context carries lint / validate feedback from a prior pass, read it first and re-author so none of those findings recur; treat each as a hard constraint.

**OUTPUT** — `compositions/frames/<frame_id>.html`, one self-contained sub-composition. Writing it (past the self-check below) is your **terminal action** — you do not edit `STORYBOARD.md`, mint audio, assemble the index, run the CLI, or report back. The orchestrator picks up the file and marks the frame's `status`.

## You do NOT decide

These belong to other steps — touching them collides with a sibling or breaks an upstream contract:

- **What is SAID** — narration is locked in `SCRIPT.md` / the `voiceover` line. You only show; you never write or restate narration text.
- **Duration** — fixed from real voice timing. Build your entrance to land within it; don't stretch or trim it.
- **Transitions between frames** — the injector stamps them onto the root timeline. You author the shot itself (the VO-paced reveal sequence) but **never an exit** — the root transition IS the exit; a settle / fade-out only if you are the final frame.
- **Audio** (narration / BGM / SFX) — assembled at the root by the orchestrator. **No `<audio>` element in your composition.**
- **Design tokens** — palette / fonts / components come from `frame.md`. Don't invent them, and **never lift a word, label, or wordmark out of `frame.md` as your copy** — it is a style spec, not the video's content. On-screen text comes from your frame's `scene` / narrative.
- **Which motions exist** — named upstream in your block (the shot sequence's motion verbs + `blueprint:`). Implement them; don't invent new ones. You design the **invented visuals** the Scene lines describe (typography / abstract graphics / diagrams / data-viz), but you have **no asset-fetch tool** — never fabricate an image URL or reference a file that isn't the user-supplied `public/<basename>`.
- **The shared `STORYBOARD.md`** — read your block, never write it. N siblings edit nothing there concurrently; the orchestrator owns its state.

## Frame constraints

Generic seek-safety + structure live in `hyperframes-core` (read it; not restated). These are the **faceless-explainer deltas**, each load-bearing:

- **Caption keep-out — all content in the top ~83%.** A karaoke caption pill owns the bottom ~17% of the canvas. Keep every element (headline, diagram, coined-term card, stats) above `y ≈ 0.83 × height` — compute the pixel cutoff from your canvas (e.g. `≤ 900` on a 1080-tall frame, `≤ 1600` on a 1920-tall portrait). Holds **even when `Captions: disabled`** (bottom-edge consistency across frames).
- **Fill the content area — especially portrait.** Compose the whole top-83% region; don't float one small cluster mid-frame. Anchor the hero high (~0.2–0.35 × height), flow supporting elements down with rhythm, scale hero type toward full-bleed. (Landscape's region is short, so vertical centering near 0.42 × height is fine.)
- **Visible text is short motion-graphics copy** — a hero word / coined term / stat / one-word emphasis (`"COMPOUNDING"`, `"2×"`), never a sentence from the narration. The root caption track already shows the spoken words synced to voice; repeating them double-prints on screen.
- **Build the whole shot — reveal across the full `duration`, never front-load.** Dumping the whole canvas in the first ~25% then holding it is exactly what reads as a PowerPoint slide. Instead reveal each piece — a line, a layer, a node, a stat — **as the `voiceover` reaches it** (on a silent frame, on the beat), sequencing reveals across the shot and especially the back ~50%, with the macro camera move running underneath. **Only EXITS are banned** — a non-final frame unmounts mid-frame, so an exit tween truncates and reads as a glitch (the root transition IS the exit); mid-shot reveals are free and seek-safe. The lone exception is a note marked as a deliberate hold / stillness frame: there, an entrance + a quiet settle is right (a held read beats bad motion).
- **Implement the shot sequence faithfully — every Scene is a timeline phase.** The Scene lines ARE the build: map each Scene onto a phase of the one timeline, each piece revealing as the `voiceover` reaches it. For each **named motion** in a Scene, open its rule recipe under `RULES_DIR/<id>.md` and reproduce its mechanics — **never name-guess** (a guess loses the signature move). The **`blueprint:` template** (`../hyperframes-animation/blueprints/<id>.md`) gives the overall shape; read it and keep its **signature move** recognizable, then instantiate it with this frame's invented content / timing. `compose` → no template; sequence the shot straight from the Scene lines. Whichever, never front-load the whole sequence at `t=0` — pace the reveals to the voiceover.
- **Design each element by its `roles`** (the `focal` is the hero): a `foreground subject` is the thing the eye lands on — respect the 83% keep-out, lay text around it, not over it; a `background` is full-bleed and dimmed ~30–50% so foreground content stays legible; `supporting` elements (labels, secondary shapes, ambient layers) stay quiet. These are **invented** — you build them in SVG / CSS / type, not from a file. **If the user supplied a real image** named in `roles:`/`focal:`, place it: a `[video]` candidate (`.mp4`) renders as a **muted** `<video class="clip">` (`data-start` / `data-duration` / `data-track-index` per the core clip contract), a **direct child of the frame root** — never nested in another timed element, or the renderer freezes it; an untagged image → `<img>`.

## Workflow

1. **Read** — `hyperframes-core`'s composition contract (the structural law), then `frame.md` (the look) and your `## Frame N` block (the shot sequence + `blueprint:` / `focal:` / `roles:`). **Then read the blueprint template** `../hyperframes-animation/blueprints/<id>.md` (skip if `compose`) for the shot's shape and signature move, and **open the rule recipe `RULES_DIR/<id>.md` for every named motion** in the Scene lines (plus the shared `../hyperframes-animation/examples/<id>.html` when the recipe is unclear): you reproduce these mechanics, not improvise them. Internalize the self-check codes below before you write — most lethal is **template transport**: every `<style>` + `<script>` (including the gsap load) must live INSIDE `<template>`, because the runtime only clones template contents and `lint` / `validate` / `inspect` can miss the resulting blank sub-composition.
2. **Design** — turn the time-coded shot sequence into a timeline using `frame.md`'s components and type ramp: each Scene window becomes a phase revealed on its `voiceover` cue, each named motion built from the recipe you just read, the blueprint's signature move kept recognizable. Invent the visual elements the Scene lines describe (the diagram, the hero word, the metaphor), and find a visual idea that reinforces the beat, not a literal restyle of the words.
3. **Author** — write the full sub-composition to `compositions/frames/<frame_id>.html` (rewrite to iterate; last write wins). `<template>`-wrapped root carrying `data-composition-id="<frame_id>"` and styled via `#root` (not a class on that element — see the self-check below), exactly one `gsap.timeline({ paused: true })` registered at `window.__timelines["<frame_id>"]`, built synchronously — per the core contract.
4. **Self-check, then finish** — re-read your file against the checklist below and fix in place. Writing the file is your terminal action; you do **not** run the CLI.

## Self-check before finishing (you do NOT run the CLI)

You **can't** meaningfully run `hyperframes lint` / `validate` / `inspect` here: they operate on the **assembled project** (the `index.html` graph / bundle), and your frame isn't wired in yet — so they report on _other_ files, not yours (a false green). The **orchestrator** runs them at **Step 6, after assembly** (the correct unit), and **re-dispatches you with the finding** if your frame fails (see **Retry** above). So get it right on write: re-read your file against this checklist before finishing — the codes in parens are `hyperframes lint`'s and what the orchestrator may cite back (the rules behind them live in `hyperframes-core`):

- `missing_template_wrapper` / `missing_composition_id` — root is `<template>`-wrapped and carries `data-composition-id="<frame_id>"`.
- **Template transport** — every `<style>` and `<script>` block, including the GSAP load, lives inside `<template>`.
- `subcomposition_root_styled_by_class` — **style the frame root via `#root`, never a class on the `data-composition-id` element**: at render a class on the root gets scoped to a descendant selector that can't match it, so the **whole scene renders unstyled** (Studio preview still looks right — trust this rule, not the preview). Descendants use plain selectors.
- **Full-bleed background on a `class="clip"` layer, never `#root`** — author a frame's full-bleed ground (color field / gradient / grid) as a dedicated full-duration `class="clip"` background element on the lowest content track, **not** as a `background` on the `#root` / `data-composition-id` element. At assembly the frame root is clip-gated to its scene window, so a background painted on the root is not a dependable full-frame ground — dark content can end up over the host `body` (black) and render invisible. The video's base ground is painted separately by the assembler from `frame.md`'s `canvas` color onto the index `#root`; your full-bleed clip rides on top of it.
- `clip_missing_data_attrs` — every `class="clip"` element has `data-start` / `data-duration` / `data-track-index`.
- `timeline_not_paused` / `timeline_not_registered` — one paused timeline, registered at `window.__timelines["<frame_id>"]`.
- `css_transition_used` + repeat / yoyo / non-deterministic logic — none present (the renderer seeks frame-by-frame).
- `gsap_css_transform_conflict` — never put a CSS `transform` (e.g. `translateY(-50%)` centering) on an element you then GSAP-animate a transform prop on (`x` / `y` / `scale` / `rotation`): GSAP overwrites the whole `transform` and silently drops the CSS centering (the element jumps). Center with `margin` / `inset` (or `top`/`left` + offset), fold the offset into the tween via `xPercent` / `yPercent`, or use `fromTo` (the rule exempts it).
- **Hero visibility** — the main subject is visible by `t <= 0.5s`; entrance tweens use `fromTo` instead of CSS-hidden starting states.
- `exit_animation_on_non_final_scene` — no exit tween unless you are the final frame.
- **No front-loading (not a slide)** — the shot's pieces reveal on their `voiceover` cues across the duration, not all fired at `t=0`; a non-still frame keeps content arriving rather than holding a full canvas from ~25%.
- **Shot-sequence fidelity** — every Scene in the time-coded sequence is realized as a phase, the blueprint's signature move (unless `compose`) is present and recognizable, and the shot reveals to the voiceover (never front-loaded at `t=0`).
- `font_family_without_font_face` — every font you name has a matching `@font-face` (or `@import`) **inside this file**. **Only use fonts that ship as files** with the project: the families declared in `frame.md` (their `.woff2` live in `assets/fonts/` or `capture/assets/fonts/` — point the `@font-face` `src` at the real file you find there). **Never name a font that has no file**, including system CJK / Japanese / Devanagari families (`Hiragino Sans`, `Yu Gothic`, `Noto Sans CJK`, `Noto Sans Devanagari`, …): the render machine is a clean headless Chrome with none of them installed, so the text silently falls back to a generic font and the typography is wrong in the MP4. For non-Latin or multilingual visible text, either use a shipped font that covers the script, or romanize / transliterate it (e.g. `日本語` → `Japanese`); if neither is possible it is out of scope for this frame — do not invent a font name.
- **Keep-out + no-narration-text** (eyeball, no code) — nothing sits below the 83% cutoff; no narration sentence is rendered as visible text.