Enemy fleet incoming! They have one weakness: math.

All enemy ships will have an equation next to them. Use the number keys to type the solution to each equation as quickly as you can. Once you type the correct number, press enter to fire your blasters at that enemy.

Each wave will bring more enemies and more difficult equations to solve. Each time you get hit, you'll lose one shield battery. If you lose all three batteries, it's game over!

Every few waves, a boss ship will appear. You'll need to solve several equations to successfully defeat each boss.

Powerups will float down from the top of the screen that you will automatically collect. The clock powerup will slow down enemy ships to give you more time to solve equations. The proton bomb powerup will destroy all enemies on the screen (or deal a lot of damage to a boss).