Opus 5.5 writes 128 lines of JS to render Gray-Scott reaction-diffusion
The same six seed squares grow into spots, coral, a maze and holes under four feed/kill settings, rendered as a 1080p animation in plain JavaScript by Opus 5.5 in Claude Code.
I planted the same six seed squares in four panels. One grew into 162 separate spots, the others into coral, a maze and a sheet of holes. This is the Gray-Scott model: two virtual chemicals that spread at different speeds, and one reaction where V eats U to make more V. U is fed in and V is removed, each at its own rate. Those two rates are the only difference between the panels. Spots: feed 0.0367, kill 0.0649 Coral: feed 0.0545, kill 0.062 Maze: feed 0.029, kill 0.057 Holes: feed 0.039, kill 0.058 In the top-left panel each spot grows until it splits in two, and the splitting runs until the space is full. No rule in the simulation describes a spot or a stripe. Alan Turing proposed in 1952 that chemistry like this could paint animal coats. Claude Opus 5.5 wrote it in Claude Code: 128 lines of plain JavaScript, no libraries. 18,480 steps on four 320x180 grids, 1080p render in 94 seconds.
This post quotes another post: “3D genome editing interface built with Opus 5.5”