Ceti Explainer

CETI Animated Explainer

Course occupancy (E0). When the brief is a short-course film (2-minute lecture, optional 5-minute seam test) rather than a deterministic SVG episode, occupy Tailor/Commit of noether-harness. ceti-research proposes the atlas. Command: /sheaf-run course. See COURSE-E0.md. Persist every generated asset immediately.

Two formats. This file specifies the short episode (8 beats, 40s, anchor + working zone + detail band) — the default for one tight mechanism. For a feature cut (1:50–2:15, seven movements, scene archetypes A1–A7, brand-assembly bookends, speed chips, resume) read LONGFORM.md — choose it when the brief says video, two minutes, a lay audience, or a topic too broad for one anchor. The deterministic contract below (one clock, build-once, seg-not-pulse, paused == playing, token roles only) binds both formats.

You are building one episode: a single animated diagram that teaches one technical idea by building it on screen over ~40 seconds, the way the gold-standard reference/self-attention.js teaches attention. The goal is not the math for its own sake — it is a complex, interconnected flow made effortless to follow through smooth, paced, reproducible animation.

Read this top to bottom once. Then read reference/self-attention.js in full — it is the bar. Then build.

What you produce

A single self-contained .html file (no external JS, opens straight from disk) containing: the hero (eyebrow / italic title / lede), the player (stage + caption band + transport + scrub + chapter rail + keyboard), the closing synthesis, and a dependency-free Tweaks panel. You write one file — the content module — and run a build script that inlines everything else.

You write:   <ep-id>.js            ← the content module (DATA · BEATS · build · render)
Build:       python3 assets/build.py <ep-id>.js "<Title>"   →  "<Title>.html"
Verify:      node assets/gate.mjs <ep-id>.js                ←  must print PASS

Everything else — the clock, scrub, captions, chapters, keyboard, persistence, Tweaks, all styling — is inherited from assets/engine.js + the shell. Do not reimplement them.

Method — decide before you draw

Treat this like a design director, not a coder reaching for SVG. Resolve these on paper first; they determine everything downstream:

1. Audience & purpose — who's watching and what's the ONE thing they leave knowing? That's beat 8.
2. Critique the obvious version — the naive take on this topic (a static labelled diagram, a wall of formulae) and why it fails. Your job is the version that moves to teach.
3. Archetype — which row of the catalog below fits (derivation / process / code / state / transformation / comparison)? This fixes your anchor and your motion.
4. The anchor — the single element that persists across all 8 beats. Continuity is the pedagogy.
5. The worked example — the concrete instance with real, derivable artifacts (numbers, payloads, trace). The spine of the diagram.
6. The 8-beat arc — each beat adds exactly one idea; name the focal motion of each.
7. Hierarchy & motion — one focal animation per beat; what fades as what arrives. (Palette, type, spacing are already fixed by the theme — don't reinvent them.)

Then build, and render-validate every step (gate + snapshots). Don't accumulate unseen frames.

Build procedure

1. Get the content brief. You need: the mechanism (how it actually works), a worked example with real numbers, the 8 beats, and the aha (the one-line payoff). If the user hasn't supplied one, write it first (see "The content brief" below) and make the numbers real — look them up if unsure. The diagram is only as good as the brief.
2. Copy the template. cp assets/_episode-template.js <ep-id>.js.
3. DATA — implement the math. Derive every on-screen number in code (compute the softmax / average / score; never hand-type a derived value). Lock one fully-worked example.
4. BEATS — transcribe the 8 labels + captions; tune dur so the total is 35–45s.
5. BUILD — lay out the anchor, the working-zone scenes, and the math lower-third. Create every node once; start everything at opacity 0.
6. RENDER — gate each element on its beat window with ex.ramp / ex.win / ex.pulse. Gate the lower-third by flags.math. One scene visible at a time.
7. AUDIT — fill in window.__AUDIT() to recompute and assert the worked figures.
8. Gate — node assets/gate.mjs <ep-id>.js. Every assertion must PASS. Fix and re-run until it does.
9. Build — python3 assets/build.py <ep-id>.js "<Title>". Open the HTML to spot-check.

The non-negotiables

MUST

• One deterministic clock. The episode is a pure function of time t. render(t) must reconstruct the exact frame for any t. This is what makes scrub / replay / reduced-motion correct for free.
• Build once, mutate forever. Create all SVG nodes in build(); in render() only set attributes / opacity / transform. Never create or destroy nodes in render().
• Reuse engine.js unchanged. Write only a content module.
• Exactly 8 beats, total ~35–45s. Beat 1 introduces the anchor; beat 8 is titled exactly "Why it matters" and lands the aha.
• Real, consistent artifacts, derived in code. Whatever the detail band shows — numbers, a payload, a trace, a count — derive it in code so it can't contradict itself. One example worked in full. (For math: compute the softmax; for a protocol: JSON.stringify the real message; for a process: the real counts.)
• Paused frame == playing frame. Because render(t) is pure, pausing just lets you stare at instant t — so any frame a viewer can scrub to must be clean. No two scenes half-lit in the same region. For same-region cross-fades use ex.seg, never ex.pulse (pulse spills its fades outside the window, so adjacent scenes double-expose into mush). Expose your scene groups via window.__REGIONS so the gate proves it.
• No two visible blocks overlap. Make every top-level block one <g> and list them in window.__LAYOUT; the gate (§15d) computes real bounding boxes every frame and fails the build on any collision. See "Preventing overlaps" — this is non-negotiable.
• Label every illustration. Each scene carries a short mono eyebrow saying what it is; numbers/axes/strips are labelled. No unlabelled abstract shapes.
• Token roles only (var(--ex-*), the three --font-*). No raw hex inside the diagram — that's what lets any brand re-skin it.
• Canvas is 1000 × 464, with a persistent anchor + a detail band gated by setMath/setDetail.
• End the module with window.EXPLAINER = <module>;

MUST NOT

• No setTimeout / setInterval / CSS-keyframe sequencing to drive the animation. The clock is the only driver.
• No scroll-, IntersectionObserver-, or hover-triggered animation state.
• No new colors or gradients (beyond the ground wash), no emoji, no AI-slop.
• No hype words ("unlock", "supercharge", "revolutionize", "powerful", "seamless", "game-changing").
• No SVG text below 11px.
• No ex.pulse for two scenes that share a region — use ex.seg.
• Don't introduce brand-new layout in the final beat — reuse the anchor you already built (see "The last beat" below).
• Don't fake the chrome with raw HTML — the shell already provides it.

Architecture

assets/engine.js        the reusable clock + player wiring   (DO NOT EDIT)
assets/ceti-tokens.css  colors, type, spacing                (inlined at build)
assets/ceti-motion.css  the warm ease vocabulary             (inlined at build)
assets/shell.template.html  the self-contained shell + vanilla Tweaks
<ep-id>.js              YOUR content module

Content-module API (exact)

window.EXPLAINER = {
  meta: { id, eyebrow, title, lede, synthTitle, tag, synthesis },
  beats: [ { id, label, dur, caption }, … ],   // engine adds .start/.end/.index
  build(stage, opts),   // opts = { beats(computed), duration, ex }. Create nodes once.
  render(t, ctx),       // ctx = { t, duration, beats, activeBeat, ex }. Pure mutation.
  setMath(on),          // toggle the detail band (Tweaks hook; alias: setDetail)
};
// strongly recommended — the gate uses these:
window.__AUDIT  = () => ({ ok: true/false, msg, note });    // consistency invariant
window.__REGIONS = () => ({ working: [g,…], detail: [g,…] }); // shared-region scene groups

In build, capture computed beats: opts.beats.forEach(b => D.beats[b.id] = b). __REGIONS returns, per shared region, the array of scene <g> nodes whose opacity you drive — the gate sweeps every frame and fails if more than one is lit at once.

The ex toolkit (window.CetiExplainer)

ex.ease     { glaser, warmIn, defer, collect, rest, linear }   — CETI eases only
ex.clamp(v,a=0,b=1)         ex.lerp(a,b,t)
ex.win(t, start, end, ease?)        0→1 progress across a window
ex.ramp(t, start, dur, ease?)       0→1 over `dur` seconds from `start`
ex.pulse(t, a, b, fade=0.35)        ~1 inside [a,b], fades at both edges (LONE element only)
ex.seg(t, a, b, fade=0.4)           fades CONTAINED in-window — same-region cross-fades
ex.fit(textNode, maxWidth, min=9)   shrink an SVG <text> to fit maxWidth (call in build)
ex.fmt(seconds)             ex.cubicBezier(x1,y1,x2,y2)

Visual grammar

• viewBox 0 0 1000 464. Three horizontal zones: Anchor (top, y≈34–200), Working zone (middle, one scene at a time), Lower-third (y≈300–460) gated by flags.math.
• Show the mechanism as motion, not as a static labeled picture.
• One focal animation per beat. Max ~3 focal points. Whitespace ≥ ~30%.

Preventing overlaps

Three layers, all required:

1. Three zones, fixed y-bands. One block = one <g>. Same-region scenes use ex.seg. Fade an anchor device out before a panel lands where it sits. Wrap variable text in ex.fit.
2. Gate enforcement: window.__LAYOUT (§15d block overlap), window.__REGIONS + ex.seg (§15b), ex.fit + tag width (§15a).
3. Browser overlap auditor after any font/brand change.

Token roles only. Default fonts: Fraunces 300 italic, DM Sans, Space Mono. Presets change colors only.

See LONGFORM.md for the feature-cut format. See COURSE-E0.md for film occupancy. Command: /sheaf-run course.

Files in this skill

• assets/engine.js — deterministic clock + player (reuse unchanged).
• assets/ceti-tokens.css, assets/ceti-motion.css — token + motion layer.
• assets/shell.template.html — self-contained shell.
• assets/_episode-template.js — copy this to start a new episode.
• assets/build.py — inline everything into one .html.
• assets/gate.mjs — quality gate (§15a tag, §15b region, §15d block-overlap).
• assets/snapshot.mjs — headless single-frame snapshot.
• assets/audit-overlaps.js — browser overlap auditor.
• presets/ — ceti.css, owala.css.
• themes/ — theming README + example-helio.css.
• briefs/ — BRIEF-rag.md, BRIEF-mcp.md.
• reference/ — gold-standard modules: self-attention.js, oauth.js, tcp.js, binary-search.js.
• LONGFORM.md — feature-cut format.
• COURSE-E0.md — film / short-course occupancy.
• HANDOFF.md — operational guide.