Here are screenshots of the projects and GitHub links.
This is probably the most interesting piece here. It's not because of how little code it takes to make this interaction happen (16 lines), it was because I got to it only by understanding what each function in p5 does. Link
1. Black canvas.
2. Black cat stencil constantly draws on the Draw loop.
3. Cursor acts as a brush and every stroke ends up behind the cat stencil.
4. Result is a "painted" cat head.