Light Particles

Make a video in the Light Particles style from ultramotion.ai: https://ultramotion.ai/styles/light-particles/
The style is an open-source Agent Skill. If you can install skills, run npx skills add sunsiyuan/ultramotion first and build it with the light-particles template (particles.js draws over a million particles with WebGL2, render.py renders, sound.py makes the sound). If you can't, write it from scratch following the description below.

[Deliverable]
- NIGHT RUN: an announcement for an outdoor sci-fi screening on May 4. A hover bike builds itself out of particles in deep space, fires its engine and lifts off, then the event name appears among the stars.
- Vertical 1080×1920, 30 fps, 24 seconds, an mp4 with music and sound effects, saved in the current directory.
- The whole video is drawn by one web page with WebGL2: 1.4 million particles, every frame a pure function of time t — each particle's position at t is computed, not simulated frame by frame, so any frame can be rendered on its own. Render with a headless browser with the GPU on, calling seek(t) and screenshotting each frame; encode with ffmpeg, then add the sound.
- Make a preview first (frames at, say, 2, 6, 10, 14, 18 and 22 s) and look at it before rendering.

[The look]
- Deep-space background #04050a. Four colours: dust #20242c, pale #e8ecf2, warm white #fff1e0, exhaust orange #ff8a3a.
- The bike is made of solid particles: each particle is an opaque dot, nearer dots hide farther ones, with normals and shading, like a point-cloud scan of a real object — never a glass box you can see through.
- Real proportions: pick one real measurement (the seat height, the length of the bike, about 1100 units) and size every part from it — a long body, long forward rods, a seat, handlebars, an engine with a glowing exhaust at the back, hovering over a landing pad.
- A share of the particles always stays behind as stars, so the flight never stops.
- Titles stay crisp: thin Avenir Next (or Helvetica Neue) made of small, dense points of light, never a fuzzy blob. Leave the title on screen for at least 3 s.
- Brightness: glowing particles add up; with this many, keep their gain low (about .3–.45). Large white areas mean it is too bright. Use bloom on the exhaust and the stars.

[How it moves — this is the style]
- Gather: particles start as a loose field of stars and fly into the next shape on paths that bow outward, arriving staggered.
- Build in order: each particle carries an arrival order, so the bike builds front to back like a scan.
- Transform: the same model in two states — parked with the engine off, then lifted with the engine lit — and the particles move between the two.
- Take over: to put a title over the scene, most particles stay where they are and only a small share (about 1.5%) flies off to form the words.
- The camera never fully stops: it glides on one smooth curve through its key positions, with a slight handheld breathing. Particles very close to the lens thin out instead of popping.

[Shots]
- 0–4.5 s · Fly in: the camera starts far outside a field of stars with the horizon tilted, and pushes in through them as the particles start to gather.
- 1–9 s · Build: the hover bike builds front to back over its pad (8 s) while the camera drops low alongside it and circles slowly.
- 9.5–12.5 s · Close pass: the camera sweeps past the tips of the long forward rods at a short distance.
- 11 s · Lift-off: the engine fires — a low boom and a whoosh — the exhaust glows warm orange, and the bike rises from about 40 to 110 units above the pad in 2 s.
- 12.5–17 s · Round the back: the camera sweeps round behind the bike to the glowing exhaust.
- 17–24 s · Title: a small share of particles swirls up and forms "NIGHT RUN" in the stars, with a smaller line "Outdoor sci-fi screening · May 4" in warm white. The camera settles at a steady rear three-quarter view under the title.

[Sound]
- A whoosh as each shape flies in and a soft shimmer as it lands; at 11 s a low boom with a 2.5 s whoosh for the engine.
- Synthesize the music in code (numpy / scipy): a slow swell in D minor at 76 BPM — pads and bass on Dm, B♭, C, A over eight bars, getting slightly louder each bar; from bar three a quiet organ line rises over it; a bell at 17.4 s as the title appears.

[Check before you hand it over]
- Look at the preview, and at a full-size crop of anything that matters.
- The bike looks like a glass box, or its far side shows through: use solid particles.
- Dark or bright specks on surfaces up close: too few particles — raise the count and spread particles by surface area.
- A grey wall at the start: the opening stars are solid too — make them loose, twinkling points spread wider.
- Big blurry blobs when the camera is close: pull the camera back.
- A title that is a fuzzy blob: lower the share of particles that form it, or the dot size.
- Everything white and blown out: lower the brightness.
- A bike that looks like a toy or a lump: check its proportions against a real one and add the parts that make it recognisable (seat, bars, lights, exhaust).
- A black frame: the browser has no WebGL2 — render with Chromium and the GPU on.