Players are required to grow a friend for the character of Peekaboo, a tiny sprite living in the grass and feeding on pure water. Players guide a water droplet through a host of obstacles to the right place. Once the water drops close enough to the target, a new friend will grow.

The game is based on the laws of physics: the water droplet evaporates in contact with a hot obstacle, and steam rises up. It changes state again once it runs into a cold barrier, drops down or freezes, and so on.