Guide the 3 sheeps back to the barn; you have to make them reach the wooden post with an arrow to complete every level. To find a way to help them reach the end is not easy, you have to create it by pushing and moving objects: it's about moving sheeps to modify the environment. At the beginning only the first of the 15 total levels is available.
You can play with any of the 3 sheeps, but each one is better for a given situation; you switch between sheeps pressing the 1-2-3 keys. Use the arrow keys to move the sheeps. If you get stuck, press the R key to restart the level. ESC key to go back to main menu.