bogsquif
An incredible portmanteau of "bouncy gif square if" (the if from gif is reused, see?).
It makes gifs with little squares bouncing off of the edges. I wanted an excuse to play with gifs and physics, so here is said excuse. It's magnificent.
License
This code is licensed under Creative Commons Zero. You can do with it whatever you wish with no restrictions at all. You don't have to credit me anywhere, even, although that's always appreciated.