I'm sure it is OpenGL ES. Like Horace said, they have said so in an interview. I didn't think their statement meant "Core Graphics which is backed by OpenGL," I think it meant what it said, which is simply "OpenGL." (ES). It makes sense, if only because Apple's documentation recommends OpenGL ES for game graphics. It's a fairly simple game, but there is still a lot going on (for example, a thread looking up scores on a remote server, an algorithm to select upcoming terrain, collision detection with platforms and monsters and nose balls) and as a developer you would want direct control over the graphics rendering at the lowest reasonable level. Also, ES is just as usable for 2D graphics as for 3D, so assuming a 2D game uses Quartz just because it is 2D is silly.