Simple physics simulation engine

I wrote this simple 2D physics simulation engine in the last few days.
The engine is written in C. Its graphics are just basic OpenGL stuff, using SDL to keep stuff cross-platform.
The hardest part was correct collision response, the rest was quite easy.
The red lines indicate the size and direction of the gravity force of a ball.

[@inmiseryseekrootbeer4966]

is this public if not can you make it.