TDD and iPhone game development platforms

I've been doing iPhone app development for a little bit of time now and I'm looking to get into game development. What are some recommended platforms? I'd like one that works well with a TDD approach and cross platform capabilities are a 开发者_开发百科plus.

I would definitely recommend Unix. The same game (granted, some of the code is different) can be export for iOS, Macs, Mac Widgets, PCs, Xbox, etc. That's mainly for 3D games, but it definitely can be used for 2D as well. Another alternative would be OpenGL. It is designed for 3D and can be used for 2D as well.