GPT-6 Astra in Codex CLI 0.156.1

Write a single self-contained HTML file that plays an original animated short film, about 50 seconds long, drawn entirely in code.

Hard technical rules:
- One file: HTML + inline <script> (+ optional inline <style>). No external images, fonts, libraries, audio files or network requests of any kind. Every frame is drawn procedurally with Canvas 2D (or WebGL if you prefer).
- The canvas renders at a fixed internal resolution of 1920x1080 and is scaled with CSS to fit the window (letterboxed, black background).
- The animation starts automatically on page load and is driven ONLY by requestAnimationFrame and the timestamp from performance.now() (measure elapsed time from the first frame). Everything on screen must be a pure function of elapsed time t, so the film is deterministic and can be captured frame by frame. No Math.random() at draw time — use a seeded PRNG / hash noise so frames are identical run to run. No setTimeout/setInterval for animation.
- Define window.FILM_DURATION (seconds). After the film ends, hold the final frame.
- Soundtrack: write an original WebAudio score (melody, chords, a little percussion or ambience, and sound cues that match story moments) synced to the same timeline. Put ALL audio scheduling in a function window.buildSoundtrack(ctx, startTime) that schedules every note/effect on any BaseAudioContext (so it also works on an OfflineAudioContext). Also expose window.renderSoundtrack = () => an OfflineAudioContext(2, 44100*FILM_DURATION, 44100) render of it returning a Promise<AudioBuffer>. For live viewing, start the soundtrack on the first click/tap/keypress (browsers block autoplay) aligned to the current film time; show a small unobtrusive "tap for sound" hint until then. Use only oscillators, noise buffers you generate, filters, gain envelopes — no samples.
- No console errors.

The film (this is a showcase of what you can animate — make it genuinely beautiful and moving):
- An ORIGINAL story with a small emotional arc (setup, a problem or longing, a turn, a warm resolution). A single consistent main character — any character you like — who appears in every scene and is recognisably the same design throughout.
- At least 4 distinct scenes, with real transitions between them (e.g. wipes, iris, match cuts, cross-dissolves, camera moves through space).
- Expressive character animation: a proper walk cycle (legs, arms, body bob), blinking, and facial emotion changes (e.g. curious, sad, surprised, joyful) that follow the story.
- A virtual camera that pans, zooms and tracks, with parallax layers for depth.
- Lighting and time-of-day changes across the film (e.g. dawn → day → dusk → night, or a storm clearing), with colour grading, glows, and shadows.
- Particles and weather (rain, snow, fireflies, leaves, dust, stars — your choice, at least two kinds).
- On-screen story text / subtitles in a tasteful storybook style that tell the story in a few short lines.
- A cohesive art direction: a warm, hand-made "paper cut-out / storybook" look is welcome (textured paper, soft edges, slight wobble), but choose what serves your story.
- End with a title of your film and a gentle closing frame.

Output ONLY the complete HTML file, starting with <!DOCTYPE html> and ending with </html>. No explanation, no markdown fences. Save it as index.html in the current directory. You may open it in headless chromium to check it and iterate.

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