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Double pendulum · gemini-3.1-flash-lite-preview

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.

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user

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.

assistant
thinking
**Developing the Core Simulation**

I'm now focused on the foundational equations of motion and how best to implement them. My priority is accuracy, and I'm leaning toward Runge-Kutta for this simulation. Visual elements like the arms and fading trail are on the to-do list, but getting the physics right first is paramount. Colorful trails are definitely envisioned.


**Defining the Model's Structure**

I've decided to build this as a self-contained HTML5 `<canvas>` application, avoiding external libraries for simplicity. The CSS will handle centering and styling. The JavaScript will manage the physics state, animation loop, calculations, and drawing. I'm focusing on defining the key variables, including angles, angular velocities, masses, and lengths, needed to calculate the double pendulum equations of motion via Lagrange's formulation. I'm now implementing the standard double pendulum acceleration formulas.


write index.html (3641 bytes)
toolResult

Successfully wrote 3641 bytes to index.html

assistant

The double pendulum simulation is complete and contained in `index.html`. It uses the Lagrangian equations of motion for a double pendulum, rendered on an HTML5 canvas with a fading, cycle-shifting trail. To view the simulation, open `index.html` in your web browser.

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

modelgemini-3.1-flash-lite-preview
vendorGoogle
harnesspi-agent
generated2026-07-22

EVALUATION

3/5 working

Double pendulum animates continuously with fading colorful trail, but pendulum motion looks too smooth/periodic, not chaotic; inputs have no effect.

Vision grade · anthropic/claude-sonnet-5

MEASUREMENTS

Raw readings from the capture, not a verdict — the grade above is the only judgement. Percentages are how much of the screen changed; the measure under-reports sparse motion on a dark background.

idle motion9.6%
on drag6.7%
on wheel6.6%
on enter + space6.6%
on arrow keys5.0%
on w/a/s/d6.0%
frame spread16 / 255
console errors0
js errors none

METRICS

runtime8.6s
tokens in4.7k
tokens out2.0k
cached0
cost / run$0.0042