Battle Gear troops were attacked by Humaliens', and they are now seeking revenge: prepare your alien troops to defend your base from the Battle Gear attack!
Click on the units you want to train, then click to place them on the battle field in the cases where it is necessary (turret, guardians, etc.). Or you can use the numeric keys 1-7 to switch fast the types of unity. Keep pressed the arrow keys left/right or the A/D keys to move around the field. Use the P key to pause. For the rest, the game will guide you as you advance.