This is a simple go program that draws rainbow lines that fall from the top of the window to the bottom. I wrote it as a toy to learn about channels and pixel graphics programming.

While the animation is running you can press spacebar to pause, up arrow to add a drop, and down arrow to remove a drop. Hold shift while pressing up or down to add or remove 10 at a time (100 with control). The acceleration of the drops can be modified with the left and right keys. You can clear all drops by pressing the r key.