All of the code is completely original, aside from jQuery (duh), and with the exception of the gravity version which makes use of code from Eric Seidel's gravity! demo, which in turn derives code from Erin Catto's ridiculously awesome Box2D physics engine. I simply didn't have enough experience with Box2D or any canvas library for that matter, and as this was purely for fun, I just wanted to see the end result without spending weeks tearing my hair out learning how. So thank you to those two fine gentlemen.
So enjoy. Prank your friends. Prank your family. And if you forget that you've opened it on your own phone, you might even prank yourself! (as have I, several times, while building it)