Animate balls dropped onto a floor that bounce with real gravity and restitution in one self-contained HTML file

# Animate balls dropped onto a floor that bounce with real gravity and restitution in one self-contained HTML file Make a small animated scene: a set of bouncing balls. Write one file, `out/scene.html`, that works opened straight from disk with no network access. `spec.json` gives the page title, the stage size and the scene parameters. **Looks are not scored**: the page is opened in a headless browser (800x600 window, UTC time zone, network blocked) and checked by objective tests only. ## Scene contract - Draw the scene on one `<canvas>` or `<svg>` stage of `width` x `height` CSS pixels (spec.json), visible on load, with `<title>` containing spec.json `title`. - Animate continuously from load (`requestAnimationFrame` or timers); no click is needed unless stated below. - Expose `window.sceneState()`, returning the scene's current state in stage pixel coordinates (origin top-left of the stage): `{balls: [{name, x, y, vy}, ...]} (y is the bottom of the ball, growing downwards)`. Extra fields are fine. It must describe what is actually drawn. - Each ball is released from rest at `drop_height_px` above `floor_y` at load (time 0 = `performance.now()` 0) and falls under `gravity_px_s2`; at each bounce its speed is multiplied by its `restitution` (the rebound speed, not the height). A ball whose rebound speed falls below 5 px/s comes to rest. `sceneState()` must return positions at the moment it is called. - The page must log no errors and throw no exceptions. Keep the file at most 200,000 bytes; no external scripts, fonts, images or URLs (inline everything). ## Checks (partial credit = share passed) 1. `self_contained`: `out/scene.html` exists, is at most 200,000 bytes, references no http(s) or protocol-relative URL, and requests nothing from the network when opened. 2. `has_canvas_or_svg`: a visible `<canvas>` or `<svg>` of at least 300x200 CSS pixels is on the page. 3. `frames_change`: over 3 s, some later screenshot differs from the first in at least 0.1% of pixels, and at least 3 of 30 screenshots differ. 4. `free_fall`: `sceneState().balls` names exactly the balls in spec.json, no ball's y goes more than 2 px below `floor_y`, and every flight between bounces seen over 3 s (5+ samples) fits a parabola in time whose acceleration is `gravity_px_s2` within 10% (fit residual at most 4 px). 5. `bounce_restitution`: for each ball at least two consecutive flights (5+ samples each) are seen in 3 s, and each flight's top height above `floor_y` is the previous flight's top height times `restitution`² within 0.07. 6. `no_console_errors`: no uncaught exception, `console.error` or browser error is logged during the run. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.