The best way to describe Dark Nebula is: it's labyrinth but on steroids. All you do is tilt your iPhone to move a rolling ball through different levels filled with various traps and obstacles.
You need to make sure you don't roll off the edges, don't hit spikes or cannons shooting at you, and roll to certain areas that open doors so you can continue. There are also springboards that let you jump to different ledges and above obstacles and items you need to push to specific places in order to get through.
It's very simple to get the hang of it and the levels get more and more interesting as you advance.
When you complete a level you get a star ranking based on how fast you completed the level, how many orbs you collected along the way, and how many times you died.
So even if you complete a level you can go back and try to do it better so that you get a gold star.
The graphics and sounds are pretty good, especially given the genre of this game, and the overall gameplay is really fun.
Cost: $0.99