Double pendulum · glm-5.3-flash
Output generated Cost / run $0.0028 Runtime 150.1s
Prompt for this run
Build a planar double-pendulum simulation on a canvas with a colorful fading trail at the lower bob. Use HTML, CSS, and JavaScript as needed. Write it to `index.html` in the current working directory using your file tools. Inline your own CSS and JavaScript. Do not use external assets, CDNs, or network requests. No third-party libraries are provided. Required behavior: - Model two point masses connected by massless rigid rods under gravity, without damping or external driving. Use the coupled equations of motion rather than independent sine-wave animations. - Use equal masses and rod lengths, gravity of 9.81 in consistent simulation units, initial angles of 120 and -10 degrees measured from downward vertical, and zero initial angular velocities. - Draw a fixed pivot, both rods and bobs, and a bounded fading trail of the lower bob. Keep both rod lengths constant and the pendulum visible. - Provide Pause/Resume and Reset. Reset restores the stated initial conditions and clears the trail. - Use a numerically stable integration scheme and time step so ordinary playback does not explode or freeze. Verify: Sample the pendulum at several moments to inspect coupled motion, connected rods, and the lower-bob trail. Pause and resume to check the motion control, then reset and confirm that the starting pose and cleared trail return.
TAKE IT TO CODE
A single self-contained HTML file — copy it and open in any browser, or reuse the prompt with your own pi-agent run.
RUN
METRICS
Transcript · 29 messages
Build a planar double-pendulum simulation on a canvas with a colorful fading trail at the lower bob. Use HTML, CSS, and JavaScript as needed. Write it to `index.html` in the current working directory using your file tools. Inline your own CSS and JavaScript. Do not use external assets, CDNs, or network requests. No third-party libraries are provided. Required behavior: - Model two point masses connected by massless rigid rods under gravity, without damping or external driving. Use the coupled equations of motion rather than independent sine-wave animations. - Use equal masses and rod lengths, gravity of 9.81 in consistent simulation units, initial angles of 120 and -10 degrees measured from downward vertical, and zero initial angular velocities. - Draw a fixed pivot, both rods and bobs, and a bounded fading trail of the lower bob. Keep both rod lengths constant and the pendulum visible. - Provide Pause/Resume and Reset. Reset restores the stated initial conditions and clears the trail. - Use a numerically stable integration scheme and time step so ordinary playback does not explode or freeze. Verify: Sample the pendulum at several moments to inspect coupled motion, connected rods, and the lower-bob trail. Pause and resume to check the motion control, then reset and confirm that the starting pose and cleared trail return.
index.html (4183 bytes)Successfully wrote to index.html
{"action":"screenshot"}Frame 1, +0ms
[Browser image supplied to model]
{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Pause\nReset","images":"attached"}
thinking
Initial pose looks right (120°, -10° from downward vertical). Let it run, then screenshot to see trail.
Initial pose matches (120° and −10° from downward vertical). Let it evolve and check trail/motion.
{"action":"motion","delta":3000}Validation failed for tool "browser": - delta: must be <= 1600 Received arguments: { "action": "motion", "delta": 3000 }
{"action":"motion","delta":1600}Frame 1, +0ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Pause\nReset","images":"attached"}
thinking
Motion is chaotic, coupled, trail works. Note: hue function used performance.now → constant hue (0.12/s → slowly varying, all red). "Colorful" — better to vary hue by trail index or time more. Fix hue to use trail length-based rainbow. Also trail fading works. Let me make hue rainbow based on index so colorful. Quick edit.
Motion is coupled and chaotic, trail fades. Trail hue is nearly constant though — let me make it truly colorful by tying hue to trail position.
{"edits":[{"newText":" trail.push({x:p.x2, y:p.y2, h:hue(trail.length*0.9)});","oldText":" trail.push({x:p.x2, y:p.y2, h:hue(performanSuccessfully replaced 1 block(s) in index.html.
{"action":"click","x":583,"y":812}Validation failed for tool "browser": - y: must be <= 800 Received arguments: { "action": "click", "x": 583, "y": 812 }
thinking
The button is below canvas (y~812), but viewport is 800. The canvas is 1200x800 so the buttons are off-screen. Better: overlay buttons on canvas. Adjust CSS: make canvas height smaller or position UI fixed overlay.
Buttons are off the 800px viewport — I'll overlay them on the canvas.
{"edits":[{"newText":" #ui{position:fixed;top:12px;left:50%;transform:translateX(-50%);display:flex;gap:10px;z-index:2;}","oldText":" #ui{Successfully replaced 1 block(s) in index.html.
{"action":"reload"}Frame 1, +0ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Pause\nReset","images":"attached"}
{"action":"motion","delta":1400}Frame 1, +0ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Pause\nReset","images":"attached"}
thinking
Hue now shifts over time (orange → gold). Colorful enough, though could cycle more; fine. Now test Pause, then Reset.
Trail is now colorful and fading. Now test Pause, then Resume, then Reset.
{"action":"click","x":556,"y":29}Frame 1, +0ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Resume\nReset","images":"attached"}
{"action":"motion","delta":1200}Frame 1, +0ms
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Frame 2, +563ms
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Frame 3, +1125ms
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Frame 4, +1679ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Resume\nReset","images":"attached"}
thinking
Pause works — frames identical. Now resume and reset.
Pause holds the frame perfectly. Now Resume, then Reset.
{"action":"click","x":556,"y":29}Frame 1, +0ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Pause\nReset","images":"attached"}
{"action":"click","x":643,"y":29}Frame 1, +0ms
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{"console":["warning: An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing."],"dom":"Pause\nReset","images":"attached"}
thinking
Reset restored initial pose and cleared trail. Also resume-after-pause motion: the bobs moved slightly after resume (frame showed a change), confirming resume works. Done.
Reset restores the initial pose (120° / −10°) and clears the trail. All checks pass. **`index.html`** — self-contained double-pendulum simulation: - **Physics**: coupled Lagrange equations of motion for equal masses/lengths (dimensionless, g = 9.81), integrated with **RK4** at a fixed Δt = 1/240 s with frame-time clamping (≤ 0.1 s) — no damping, no explosion, no freeze. - **Initial conditions**: θ₁ = 120°, θ₂ = −10° from downward vertical, zero angular velocities. - **Rendering**: fixed pivot, both rods (constant length) and bobs, plus a bounded 400-point fading trail of the lower bob with hue cycling along the trail. - **Controls**: Pause/Resume and Reset (restores initial conditions and clears trail), overlaid on the canvas. **Verified in-browser:** - Initial pose matches the specified angles; rods stay connected at constant length through chaotic motion. - Trail is colorful and fades with age; motion is visibly coupled (energy exchange between arms), not independent sine waves. - Pause freezes the frame exactly (4 identical sampled frames); Resume continues, and Reset returns the starting pose with an empty trail. **Not verified:** long-run energy drift over many minutes and exact conservation accuracy — only stability and qualitative chaos were checked.