Animate a junction where cars obey a traffic light's timed sequence in one self-contained HTML file

# Animate a junction where cars obey a traffic light's timed sequence in one self-contained HTML file Make a small animated scene: a road junction with a traffic light. 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): `{light: <the light showing now, one of the spec.json phase names>, cars: [{x}, ...]}`. Extra fields are fine. It must describe what is actually drawn. - Cars drive left to right along one lane; `x` is the front of the car in stage pixels and may wrap back to the left edge after a car leaves the stage. The light runs through `phases` in the order given, starting at the first phase on load, each for its `s` seconds, then repeats. Cars may only cross `stop_line_x` on green; on any other phase they stop at the line or queue behind the car ahead. Keep the traffic dense enough that a car is waiting at the line during the non-green phases. - 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. `light_sequence`: over 3 s `sceneState().light` only takes spec.json phase names, changes only to the next phase in spec.json order (wrapping round), changes at least 3 times, and every phase seen from its start to its end lasts its `s` seconds within 0.25 s. 5. `cars_obey_lights`: `cars` has exactly spec.json `cars` entries; between two samples a car's x only goes from below `stop_line_x` to at or above it when the light is green in one of the two samples; some car moves while the light stays green, and some car waits (moves under 0.5 px) within 60 px before the stop line while the light stays on a phase other than green. 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.