On the left of the map, you will see a small town with a few houses and some tiny snowmen. They must be protected! If all of them die, you lose.

All sorts of enemies will walk onto the screen from the top right and bottom right. Anything that isn't a snowman is an enemy and must be killed (if enemies get to your town of tiny snowmen on the left, they will shoot and kill the snowmen - so make sure you keep enemies away). Alongside the enemies spawning from the right, there will be snowmen - don't shoot them, as this will also kill the snowmen in your town.

When you kill enemies, you get money! You can use money to purchase turrets (Press T then click on the screen to buy and place one).

You win once you kill 128 enemies.