Who says a tank driver doesn't need a brain? Put some thought into your shooting!
Mouse - Aim & Shoot.
1-4- Change Color.
Space- Use Energy Bar.
Destroy all tanks, matching the color of the shot to the tank being shot. After buying upgrades, you can collect energy from the tanks you shoot. Once you've filled a color's energy bar, you can use it (with Space) to send out a laser shot.
In Rampage Mode, there are no colors or upgrades, just 1 life.