ASCII 现场编码游乐场

Build a runtime that measures one monospace glyph, computes cols and rows for the viewport, and every animation frame calls a user function once per cell with normalized coordinates, time and pointer position. Let the function return a character (or an object with char and color), store results in a flat buffer, and diff against the previous frame so only changed rows are written as innerText spans. Ship a tiny math kit (vec2, length, smoothstep, a signed-distance circle and box) so users can turn distance values into a density ramp like ' .:-=+*#%@'. Add a hot-reload text editor beside the output for live coding.