Self-running 3D Rube Goldberg machine

Build a 3D Rube Goldberg machine that runs itself, as a single self-contained index.html in the current directory. The chain, in order: 1. A marble is released at the top and rolls down a series of zig-zag ramps. 2. It knocks over a line of at least 12 dominoes. 3. The last domino tips a seesaw, which launches a small ball into a hanging bucket. 4. The bucket's weight pulls it down; its rope runs over a pulley and yanks a bell, which visibly swings. 5. The same motion raises a flag up a pole. The flag reaching the top is the finish. Rules: - Write the physics yourself: no physics library. Every motion after the marble is released must come from your simulation (rigid bodies, collisions, constraints, rope/pulley). No keyframed animation or tweened motion of any machine part. - You may load three.js from a CDN for rendering. Nothing else external: no images, models, or fonts. - It must run with no user input: start automatically on page load, use a cinematic camera that follows the action, and complete the whole chain in about 15–20 seconds. After the flag is up, hold for 2 seconds, then reset and replay. - Deterministic: fixed timestep and no unseeded randomness, so every run looks the same. - Fill the browser window. It will be screen-recorded at 1280×720. - No on-screen text or UI of any kind. - Make it look good: lighting, shadows, materials, and a setting that makes it feel like a real contraption.