Tower defense game set in space.Defend the space lanes from the invading aliens and stop them from reaching the wormhole back to Earth.35 levels15 alien types7 tower types that can be upgraded up to 3 timesReplay previously completed levelsThe most expensive tower is not always the best one for the job.Choose them carefully as a lesser tower that has been upgraded may do more damage to certain types of aliens.Later levels can't be completed without a mixture of powerfull and weaker towers combined.