While Icy Tower does not provide different levels or towers to play, it does offer two modes. It's a great way to increase your score dramatically and quickly move up the tower. Combos can be “chained” in one bigger combo if you keep making large jumps in quick succession. A combo is a jump from one platform to another platform at least two floors above.
Combos are performed by building up your characters speed (by running fast enough, bouncing off walls, falling, etc.) and jumping. To help you move up the tower faster and earn more points there are “combos”.