Animate a mass on a damped spring released from rest in one self-contained HTML file

# Animate a mass on a damped spring released from rest in one self-contained HTML file Make a small animated scene: a damped mass-spring oscillator. 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): `{x: <displacement of the mass from rest, px, positive = stretched>, v: <velocity, px/s>}`. Extra fields are fine. It must describe what is actually drawn. - Time 0 is `performance.now()` 0 (seconds = `performance.now()` / 1000). Treat px as the length unit for displacement (the dynamics only need the rate constants: damping rate = damping_ns_per_m / (2 × mass_kg), natural frequency = √(k_n_per_m / mass_kg)). The mass is released from rest, so its velocity at time 0 is 0. Draw the spring from a fixed anchor to the mass, `rest_length_px` long at rest. `sceneState()` must return the state 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. `damped_position`: at every sample, `x` is within 1.5 px of the exact displacement of a damped mass-spring released from rest at `x0_px` at time 0 (mass `mass_kg`, stiffness `k_n_per_m`, damping `damping_ns_per_m`). 5. `damped_velocity`: at every sample, `v` is within 3 px/s + 2% of `x0_px` × the damped angular frequency of the exact velocity. 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.