ROM Hacks are great fun. But sometimes you want to make something more complicated than modifying an existing game can allow. Unfortunately, the drawback to the ground-up approach is that a physics engine must be developed. The physics play a critical role in the overall fun of a Sonic game, and so must be tuned to perfection. These physics guides will hopefully make that process easier. Whether you are using Game Maker, Flash, C++, or anything else, they should be an indispensible reference for making sure your physics are as accurate as possible to the original Sonic. Even if you want to make modifications or improvements, you have to know where to start from!

Sonic Physics Guide