Canabalt

What would possess someone to leap through a plate glass window onto a rooftop below? Since CANABALT never shows you what's chasing you, you have no idea. But it must be pretty bad, because you never stop running -- unless you miss and fall to your death, or run at high speed into a mysterious piece of machinery that fell from the sky. Canabalt is very simple: tap to jump, and the man runs as fast as he can. Avoid obstacles on the rooftops -- not because you’ll die, but because they may slow you down enough to keep you from making your next jump.

For such an easy mechanism, Canabalt does an amazing job of setting the mood: using pixelly grayscale graphics, it describes its world more by suggestion than outright depictions. You see giant robotic shapes in the far distance, but only in silhouette; jets fly past, shaking the ground; buildings crumble as you run across them. The sound effects are sparse but pitch-perfect, from shattering glass to the differing footsteps when you run across a crane. And the little details are amazing -- flocks of birds fluttering up as you run through, the way your jacket flaps while you run. Not that you'll have time to admire them -- you'll be too busy running.