Double pendulum · claude-opus-5
Output generated Cost / run $0.2465 Runtime 81.6s
Prompt for this run
Simulate a chaotic double pendulum on a canvas using the correct equations of motion, drawing the arms and a colorful fading trail of the tip.
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.
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METRICS
Transcript · 8 messages
Simulate a chaotic double pendulum on a canvas using the correct equations of motion, drawing the arms and a colorful fading trail of the tip.
thinking
I'm building a single-file double pendulum simulator with RK4 numerical integration, adding a trail system that uses HSL colors to fade older points. I'll include interactive controls for play/pause and reset, adjustable parameters like pendulum lengths, masses, gravity and damping via sliders, plus options for trail length and maybe a ghost pendulum for comparison.
/tmp/ws/index.html (12242 bytes)Successfully wrote 12242 bytes to /tmp/ws/index.html
thinking
I need to clean up a stray CSS class with extraneous text, and make sure the system initialization properly toggles when main.y is present.
{"path":"/tmp/ws/index.html","edits":[{"oldText":" .eq{font:11px/1.6 ui-monospace,monospace; color:#6f7characters}\n","newText":""}]}Successfully replaced 1 block(s) in /tmp/ws/index.html.
thinking
The Ghost initSystems function reads main.y after reinit, which works fine since it's passed as arguments and evaluated first. The onchange handler for ghosts also reads main.y before reinit, so that's consistent. Trails stay cleared throughout, which is good. Let me do a quick syntax check with Node to make sure everything's solid.
{"command":"cd /tmp/ws && node -e \"const s=require('fs').readFileSync('index.html','utf8');const m=s.match(/<script>([\\s\\S]*)<\\/script>/js ok
Done — `/tmp/ws/index.html` - **Physics**: exact double-pendulum equations of motion (point masses, Lagrangian form) integrated with RK4 at a fixed 1/1200 s step, plus optional viscous damping. Live readout of θ, ω and total energy (a good check: E stays ~constant with damping 0). - **Visuals**: additive-blended fading trail of the tip whose hue cycles along its length, glow, motion-blur wash, mass-scaled bobs. - **Chaos demo**: 5 ghost twins offset by 1e-5 rad show exponential divergence (Δθ₂ shown in HUD). - **Controls**: lengths, masses, gravity, damping, speed, trail length; pause (Space), reset, clear; drag either bob to set initial conditions.