Gameplay has you zooming across the screen by accelerating (by pressing A) on the downslope of each hill, gaining as much air as you can, then pressing down at the right moment to slide gracefully down across the next downslope (as opposed to hitting a hill square on and losing momentum). The mechanic is simple and keeps you going for “just one more turn” longer than it has any right doing.
Presentation has the rainbow ranting about how humanity has destroyed the world and deserves to be destroyed itself; depending on your perspective, this will be somewhere between hilarious and prescient (or, in my case, a bit of both). 80 Microsoft Points (get it before humanity finishes the Earth’s destruction and you can’t get it anymore).
Here’s what the developer (Kindling) has to say about the game:
“Rainbow is unhappy with the way things turned out down below. He wants a clean slate. Help him wipe humanity off the face of the Earth. – Slide down hills to build momentum – Master gravity to get awesome air – Smash into three kinds of power-ups – Play new hills every time you start up – Eat lots of people – Conquer 45 challenges – Hear Rainbow’s story”