Eliminate the invading force intent on taking Space Station Xorbe in Earth's orbit. If the station is captured then it will become a staging ground for the invasion of Earth itself. You have a huge arsenal of weapons and defensive mechanisms at your disposal - use them wisely and you may prevail.
All aliens first point of attack is from the air - so it is important to select, place and upgrade your air defenses carefully.
If your air defences fail to block the air assault the aliens will establish beachheads (shaded green) to place their ground towers. At this point or earlier place your ground defence towers to eliminate the aliens before they take too much of your space station.
Aliens like to shoot as they approach the station and once they have established a foothold on the ground. Any damage caused to your towers can be repaired using medical units affectionately call Ned Meds. Place these units near damaged towers and they will slowly repair them.
Recovering Alien Ground
The aliens will mark ground (green shade) prior to establishing a tower on it. Before you can build on this land again, you need to clean it with the 'Meaner Cleaner' tower.
This is a special use-once tower that can be used to make a big hit on a established alien ground tower. Once the tower is placed it will charge until ready (click on it to see the charging process). When ready click the charge icon and then click the enemy tower you want to destroy. Warning - the nuke can hurt your own units.