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diff --git a/docs/superpowers/specs/2026-07-12-mixamo-hero-hook-design.md b/docs/superpowers/specs/2026-07-12-mixamo-hero-hook-design.md
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+++ b/docs/superpowers/specs/2026-07-12-mixamo-hero-hook-design.md
@@ -0,0 +1,64 @@
+# Mixamo Hero Hook — Design
+
+**Date:** 2026-07-12
+**Status:** Approved
+
+## Goal
+
+Use one Mixamo mocap clip (**jumping jacks**) as the "eye-candy hook" on the
+three primary marketing surfaces, while the procedural DSL stays the source of
+truth everywhere a visitor actually engages.
+
+Role of Mixamo = **pure attention-grabber**, not a claim about tool output. It
+is delivered through the real `clip "<name>"` DSL directive (clip-back), so the
+document honestly declares what it plays; deleting that one line drops it to
+procedural.
+
+## Scope — three surfaces, one directive
+
+All three read the same `spec/examples/jumping-jacks.posecode` document and the
+same `SHOWCASE_CLIPS` map, so a single directive lights up all of them:
+
+1. **Landing hero** (`playground/index.html` + `landing.ts`) — already wired to
+   `clips: SHOWCASE_CLIPS`; needs no code change once the directive is present.
+2. **Playground default movement** — first thing shown on `/play`.
+3. **Main README GIF** (`docs/media/jumping-jacks.gif`) — re-rendered from the
+   clip via the existing capture script (it drives the real playground).
+
+**Out of scope / unchanged:** the sub-three README GIFs (`deadlift`, `squat`,
+`lateral-raise`) stay **procedural**. No other preset changes.
+
+## Changes
+
+1. **`spec/examples/jumping-jacks.posecode`** — add `clip "jumping-jacks"` so the
+   doc plays the retargeted Mixamo motion when the skinned figure is active.
+2. **`playground/public/clips/`** — rename the re-uploaded Mixamo file
+   `Jumping Jacks.fbx` → `jumping-jacks.fbx` to match the `SHOWCASE_CLIPS` key
+   (`jumping-jacks → /clips/jumping-jacks.fbx`). Files remain gitignored /
+   CDN-served; this only reconciles local + CDN naming.
+3. **`playground/src/main.ts`** — introduce `DEFAULT_PRESET_ID = "jumping-jacks"`
+   and boot from it (approach A), leaving the library list order unchanged.
+4. **Re-render** `docs/media/jumping-jacks.gif` via
+   `node scripts/capture-gifs.mjs jumping-jacks`.
+
+## Honesty / consistency guardrail
+
+Only the jumping-jacks doc declares a clip. Every other preset, and the sub-3
+GIFs, render procedurally — so the moment a visitor browses the library or edits
+the default doc, they see real DSL output. The default doc visibly contains the
+`clip "jumping-jacks"` line, so the mechanism is transparent, not hidden.
+
+## Verification
+
+- Browser preview: confirm the landing hero and the playground default both play
+  the Mixamo jumping-jacks loop (not the procedural fallback), and that the loop
+  reads cleanly through the neutral standing pose.
+- Confirm removing the `clip` line falls back to procedural.
+- Inspect the re-rendered GIF before committing.
+
+## Risk / history note
+
+Last session the landing jumping-jack "looked too bad" — that was the
+*procedural* fallback after clips were dropped (`26a5e68`). Re-adding the Mixamo
+clip is expected to be the fix. If the mocap loop itself reads poorly, adjust
+loop/framing before re-rendering the GIF.
diff --git a/playground/src/main.ts b/playground/src/main.ts
index d7b3731..b836a8e 100644
--- a/playground/src/main.ts
+++ b/playground/src/main.ts
@@ -19,6 +19,12 @@ import {
 import type { PosecodeEditor } from "./editor.js";
 import { PRESETS } from "./presets.js";
 import { SHOWCASE_CLIPS } from "./clips.js";
+
+// The movement shown on first open (no shared link). Jumping jacks plays the
+// Mixamo showcase clip, so the playground greets visitors with polished mocap
+// while every other preset — and the editor once you engage — stays procedural.
+// Falls back to the first library entry if the id is ever removed.
+const DEFAULT_PRESET = PRESETS.find((p) => p.id === "jumping-jacks") ?? PRESETS[0]!;
 import { renderWarnings } from "./warnings.js";
 import llmPrompt from "../../spec/llm-authoring.md?raw";
 
@@ -506,9 +512,9 @@ if (sharedSource) {
   initialDoc = sharedSource;
   intro.hidden = true;
 } else {
-  initialDoc = PRESETS[0]!.source;
-  currentPresetId = PRESETS[0]!.id;
-  libCurrent.textContent = PRESETS[0]!.label;
+  initialDoc = DEFAULT_PRESET.source;
+  currentPresetId = DEFAULT_PRESET.id;
+  libCurrent.textContent = DEFAULT_PRESET.label;
 }
 
 // Boot the two heavyweights (CodeMirror editor + Three.js renderer) after the
diff --git a/spec/examples/jumping-jacks.posecode b/spec/examples/jumping-jacks.posecode
index 47caa24..f8a8ad2 100644
--- a/spec/examples/jumping-jacks.posecode
+++ b/spec/examples/jumping-jacks.posecode
@@ -1,5 +1,6 @@
 posecode exercise "Jumping jacks"
   rig humanoid
+  clip "jumping-jacks"
   pose start = standing
 
   step "Out" 0.5s settle: