You play as a gray space dude running through a tunnel in space. This character is now known as the Runner. You need to maneuver around or jump over the holes in the floor, because if you fall, the level restarts. The game can get quite difficult at times, there are plenty of tricky levels in the game.
When you touch the wall of a tunnel, gravity changes so that the wall is now the floor. You can go all the way around the tunnel this way, and some levels even require it.
The game includes 50 levels in Adventure mode, which start out easy but get to be quite hard by the end. Infinite mode includes an unlimited number of randomly-generated levels, and the Kongregate version of the game has an enormous selection of user-created levels.
The game includes three speed settings: Normal, Fast, and Intense. Fast is 1.5 times faster than Normal, and Intense is twice as fast as Normal. Intense speed isn't unlocked until you finish either Adventure or Infinite mode on Normal or Fast.
Intense speed acts like a separate game mode. When you select it, your progress disappears, and you have to replay the game from Level 1. Likewise for Infinite mode, which restarts from 20% difficulty. Your old progress is restored when you select Normal or Fast.