Double pendulum · qwen3.6-35b-a3b
Output generated Cost / run $0.0030 Runtime 72.3s
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 · 7 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.
thinking
The user wants me to build a planar double-pendulum simulation with: 1. Double pendulum physics using coupled equations of motion 2. Colorful fading trail for the lower bob 3. Pause/Resume and Reset controls 4. Numerically stable integration (RK4) 5. Initial conditions: θ1=120°, θ2=-10°, ω1=ω2=0 6. Equal masses, rod lengths, gravity=9.81 Let me write a complete, self-contained index.html file with inline CSS and JS. The equations of motion for a double pendulum: - Two point masses m1, m2 connected by massless rods L1, L2 - Using Lagrangian mechanics, we get coupled second-order ODEs I'll use RK4 integration for numerical stability. Let me build this carefully.
/tmp/job-QEOAgm/index.html (8605 bytes)Successfully wrote to /tmp/job-QEOAgm/index.html
thinking
Now let me open the file in the browser and inspect it.
{"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.","error: cos is not defined"],"dom":"Planar Double Pendulum\nPause\nReset\nθ₁=120° θ₂=-10° | Initial angular velocities: 0 | Running","images":"attached"}
thinking
The error is clear: `ReferenceError: cos is not defined`. I used `cos` instead of `Math.cos`. Let me fix all trig function calls. I need to scan the code and replace all bare `cos`, `sin`, `tan`, `sqrt`, etc. with `Math.cos`, `Math.sin`, `Math.sqrt`, etc. Let me read the file to see all the issues.
I see the error: `cos is not defined` — the trig functions need `Math.` prefix. Let me fix all of them. {{< read path="/tmp/job-QEOAgm/index.html" >}}