Lots of games on the iPhone skew more casual, both because the touchscreen doesn't exactly make for precise controls all the time, and also because a lot of developers are aiming for the iPhone's much wider audience than most gaming platforms. But 1-bit Ninja is obstinately the exception to this -- it's unapologetically retro and decidedly hardcore. The nearest reference is Super Mario Bros, but not Super Mario Galaxy or the more recent 3D interations. Nope, this one goes back to Super Mario Land on the GameBoy, when Mario could only move forward, and had to make some spectacularly timed jumps to explore the land and fully discover its secrets.
1-bit Ninja isn't just a 2D platformer -- it does have a really wild 3D angle (accessed by swiping the top of the screen) that will show off some new heights or extra secrets to find. Bu