Oolite is a space sim game, written for OS X in Objective C using Cocoa and OpenGL. It was written as my response to the withdrawal of Elite - The New Kind from the internet. Although inspired by the work of Christian Pinder, following David Braben and Ian Bell, the work is an independent interpretation and expansion of the original game.
Oolite is designed as a small game that is easy for users to pick up and expand upon. Almost every aspect of the game can be modified using simple, free graphics packages and text-editors.
More detailed version changes are here.