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.

用 three.js 做的自动循环鲁布·戈德堡机械，物理全手写，镜头跟拍，按 1280×720 录屏。 英文标题：Self-running 3D Rube Goldberg machine 中文提示词译文： 构建一个能自己运行的 3D 鲁布·戈德堡机械，做成当前目录下的单个自包含 index.html。 连锁反应依次为： 1. 一颗弹珠从顶部释放，沿一系列之字形坡道滚下。 2. 它撞倒一排至少 12 块的多米诺骨牌。 3. 最后一块骨牌压翻跷跷板，把一个小球弹进悬挂的桶里。 4. 桶的重量让它下坠；绳子绕过滑轮，猛拉一个铃铛，铃铛明显摆动。 5. 同一个动作把旗子沿旗杆升起。旗子升到顶就是终点。 规则： - 物理自己写：不用物理库。弹珠释放后的每个动作都必须来自你的模拟（刚体、碰撞、约束、绳索/滑轮）。机械的任何部件都不能用关键帧动画或补间动画。 - 可以从 CDN 加载 three.js 用于渲染。其他外部资源一概不用：不用图片、模型或字体。 - 必须无需用户输入就能运行：页面加载后自动开始，用跟随动作的电影感镜头，整条连锁反应在大约 15–20 秒内完成。旗子升起后停留 2 秒，然后重置并重播。 - 确定性：固定时间步长，不用未设种子的随机数，保证每次运行看起来都一样。 - 铺满浏览器窗口。它会以 1280×720 录屏。 - 画面上不要有任何文字或 UI。 - 要好看：灯光、阴影、材质，以及一个让它像真实装置的场景。 使用工具：threejs, claude-code 需要输入：none 原始发布：https://x.com/leogao25/status/2102544078927741369 来源许可/权利说明：CC BY 4.0（仓库采用 CC BY 4.0；社区 Prompt 与视频权利归原作者并受原帖条款约束，保留完整归属）