Your bunker is in the middle of the battleground and infected enemy mutants will come to destroy you from every angle. Move the mouse to aim your bunker's cannon. Click to fire a bullet (click and hold if you've obtained the flamethrower or hailstorm abilities). Use the three spells at opportune times (flare, blizzard and restore). Spend gold that you've earned from mutant kills wisely to upgrade your bunker and abilities. There are 20 levels and as you progress through the game you will meet stronger and faster enemies. On each level, kill all enemies before they reach your tank to earn a master badge for that level.