Cascade

Karel's piano as a body of liquid light with a continuous surface — thousands of particles running a smoothed-particle fluid on the GPU. The fluid is binned into 24 cells, and each cell's density and current drive an independent granular voice that cuts grains straight out of his recording. The currents don't filter a loop — they generate the sound, grain by grain. Raise both hands to push the liquid, or drag with the pointer; leave it be and it plays itself.

Fully playable with the pointer alone. Allow the camera to push the liquid with two hands instead — shoulders and wrists are all it needs, seated is fine.