The goal is to protect your sun from invading enemies by firing missiles and building turrets. The enemies come in waves and shoot at you or your sun, whichever is closest and in range. Survive as many waves as you can until you get bored.

The item you get because it’s too dangerous to go alone is a shield that is active while you hold down space bar. It loses energy while in use and even more if it gets hit by enemy fire but it slowly recharges while not in use.