旋转字符甜甜圈

Sample a torus with two nested angle loops, rotate each point and its normal by two time-varying angles, and project with a simple perspective divide onto a character grid. Keep an inverse-depth buffer per cell so nearer samples win. Compute luminance as the dot product of the normal with a fixed light vector and pick a glyph from a ramp of about a dozen characters. Join the rows into a string and set it as textContent of a <pre> every frame; optionally render the same samples as tiny canvas dots to show the parallel.