MOSS: A Paint Program with Programmable JavaScript Brushes

MOSS is a fun MS Paint-style drawing app with an interesting twist: each brush is a tiny JavaScript program that defines how it behaves as you draw.

There are dozens of community brushes to experiment with, ranging from whimsical patterns to abstract generative art. The best part is that you can inspect and live-edit the JavaScript code for any brush directly in the canvas. It’s a neat, creative playground to tinker with for a few minutes.