Pingus

Pingus is a Lemmings-based puzzle game licensed under the GNU GPL, with 77 levels available and runs on popular operating systems such as Windows, Linux, MacOSX and others.
The game is presented in 2D. Players give orders to a group of small animals and have to guide them through each level. Since the animals walk on his own, the player can only influence them by giving a command, such as building bridges, digging a hole or redirect all animals in the other direction. The goal of each level is to reach the exit, to a combination of some of the commands necessary.