Clyune Component GalleryFireworks · How it works & code
particle fireworks with gravity and trail
Runtime logic
Visiting `/canvas/fireworks`, DemoHost lazy-loads `demos/kits/kit-canvas.js` (registry `mod: 'kit-canvas'`) and calls `mount(host, { variant: 'fireworks' })`. mount resolves the variant to family `fireworks`; `withControls` builds the control panel (5 presets + sliders). `createCanvasStage` creates the `<canvas>` (HiDPI ≤ 2×, ResizeObserver) and the info panel. The family’s `build(S)` initialises state and returns the per-frame callback. Every `requestAnimationFrame`: read controls, advance a speed-scaled clock (dt ≤ 50 ms), run the frame callback; returned readouts go to the info panel. Pointer down/drag/move updates the interaction (drag handles, hover readouts); when untouched and auto-demo is on, the pointer follows a Lissajous path. Changing parameters: colour/speed/size apply live; structural ones remount; leaving the page cancels rAF, removes listeners and frees resources.
Environment
Canvas 2D: 2D canvas drawing; requestAnimationFrame: Display-synced animation loop; ResizeObserver: Canvas follows container size; Pointer Events: Unified mouse/touch/pen events; devicePixelRatio: Crisp HiDPI rendering (capped at 2×) · react 18.3.1, react-router-dom 6.30.6, vite 5.4.21
Dependencies
react 18.3.1
Imported APIs
withControls — Wraps the demo in the shared control panel (presets, sliders, reset); hot-updates or remounts on change; paramsFromSpec — Turns the spec (colour/speed/size/count/extras) into control-panel parameter definitions; createCanvasStage — Shared Canvas 2D stage: canvas + info panel, HiDPI, one rAF loop, pointer state, idle auto-pointer; rng — Seeded deterministic PRNG (same seed, same result); hueOf — Hue of a colour (0–360°); TAU — Constant 2π; fmt — Number formatting (fixed decimals); F — Formula block HTML; S.get — Reads current control values; S.onDown — Pointer down; S.clear — Clears with the background colour (translucent = trails); S.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.createLinearGradient() — Creates a linear gradient; ctx.fillRect() — Fills a rectangle; ctx.beginPath() — Starts a new path; ctx.moveTo() — Moves the pen without drawing; ctx.lineTo() — Adds a straight line to a point; ctx.stroke() — Strokes the current path
Source code
frontend/src/demos/kits/kit-canvas.js: FAM.fireworks (L127-L178)
Code walkthrough
L129-129: Control definitions (colour/speed/size/count/extras): primary color, spark thickness, sparks per burst, gravity g, air resistance k, auto-fire interval s. L130-130: Preset buttons: name → parameter overrides (5). L131-139: Info-panel content: live rows(v), formula, notes, params, steps. L140-177: Init function: sets up state and returns the per-frame callback: registers pointer handlers `S.onDown`; draws with Canvas 2D `createLinearGradient`, `fillRect`, `beginPath`, `moveTo`, `lineTo`, `stroke`; math via `Math.max`, `Math.sqrt`, `Math.round`, `Math.min`, `Math.cos`, `Math.sin` …; returns readouts `sparks`, `rockets`, `shots`, `g`, `k`, `v0`, `h` … to the info panel.
Principles
Rocket: Raise h, First Speed v₀ = √(2gh) Spark: · v +g, so v(t)=u · e^(−kt) + … Fly as far as possible when gravity is not available u / k Each rocket is fired straight from the bottom v₀ = √(2gh) Calculating, at the speed of the target 0, Then it explodes. The explosion creates a circle of sparks, each at a different start u And direction. Air resistance reduces speed by index e^(−kt)), Gravity slows them down, so they form“Weeping willow”The same trajectory. The spark has a lifetime, the older it gets, the darker it disappears.