Liquid Layers is a fun interactive site where you can engage with a sea of colorful fluid. I like that you can play around with a long list of variables that affect the way the liquid moves.
You can change the brush size, density, color, and more. When you move your pointer around in the colorful particles, you can splash them around and mix them up. If you want to fiddle around for a few minutes on your computer in between serious tasks, this is a nice way to take a little brain break.
See also: Watch this nanolab print liquid 3D structures
