I don't get it. Given your self-proclaimed skillset (below) you are trying to tell us you genuinely don't know how to increment a number in Lisp?
Expertise:
Computer, Video, and Mobile Games (PC/Mac/Consoles/iPhone/Android)
Real-time physics simulation
Game-logic and character AI
3DS Max scripts and plug-ins
Unity game engine
OpenGL/OpenGL ES/Cg Shaders
C/C++/Objective-C/Java/Python/Lua/Common Lisp
