Doodle Jump is an amazingly fun game. There are broken platforms that crumble if you jump on them, springs that fly you higher if you jump on them, UFOs that will abduct you unless you shoot them first, black holes that will suck you in if you get too close, and various monsters that you need to kill.
As you jump higher and higher, the platforms start moving, the monsters start appearing and the game gets progressively more challenging. Along your way up, you will see markers on the side of the screen indication how high other players of Doodle Jump around the world have managed to get to.