Browser animation

Codex generated the JavaScript in this directory specifically for this example. The citations in ../modes.toml support the governing equations, but the numerical constants, damping, speed limits, boundary handling, and time stepping are choices made for this demo.

driver.js owns the requestAnimationFrame loop. It reads the one-row Bokeh ColumnDataSource, observes the paused state, and calls the active kernel. Python replaces the kernel's CustomJS.code and sends newly initialized NumPy arrays when the mode changes or the viewer resets the simulation.

Each kernel receives two Bokeh models through CustomJS.args:

• particles contains the x, y, vx, vy, life, and normalized speed arrays.
• centers contains the two draggable field-center positions.

For each frame, the driver passes action: "step", strength, rate, time, and dt in cb_data. Python handles mode-specific initialization, so the kernels only advance the simulation between resets.

Python prepends helpers.js to each kernel. The helper functions implement speed limiting, periodic boundaries, and integration without allocating objects inside the 50,000-particle loops.

Bokeh serializes the float32 NumPy arrays for a reset as binary WebSocket buffers. The arrays stay in the browser during animation, so particle positions do not cross the WebSocket for each frame.