To play the game you need to shoot down the UFOs by ricocheting your shots of the walls. The game gets harder each level and you only have one life for the whole game, so make sure that the Earths shield is not completely drained or it's game over. There are Shield boosts to pick up which will help you out throughout the game.
Be careful when shooting as your shots will be destroyed if you hit any force fields. You do have some special weapons to pick up through the game, these will pass through force fields once activated (after they've been deployed.)
Also be careful not to waste your special weapons in the Thunder & Lightning levels. They will be destroyed if they are not activated before being hit by lightning.
For Example, Level 3 is a Thunder & Lightning Level. If you pick up any special weapon and deploy it by holding down CTRL, if you do not activate it before Lightning happens it will explode in mid-air and you will lose the weapon. The same thing happens if you hit a force field, the UFO or the Earth (before activating the weapon.)
L/R Arrow Keys / A, D - Move Tank Left and Right
Space - Fire
U/D Arrow Keys / W, S - Navigate Special Weapons
CTRL (Hold Down) - Deploy Special Weapon
CTRL (Release) - Activate Special Weapon
P - Pause / Resume . Defend the Earth from alien invaders by bouncing your shots off the walls....