The alien invasion has begun! You control the last platoon of soldiers that have survived the onslaught. Protect your bases over 5 stages across the USA. Once all the bases are destroyed the aliens will control everything! Each stage consists of 4 waves of aliens, each wave stronger than the last. At the end of each stage there is a terrible alien monster to defeat!
Command your soldiers to aim and fire using the mouse.
Roll the mouse cursor over dropped coins and ammo boxes to collect them.
[SPACEBAR] = Purchase more ammo.
 -  = Quickly purchase one of eight troop types.
[Q] to [T] = Purchase one of the five upgrades.