Colony Defense

Colony Defense is a tower defense game. Player takes place of GalCon war academy graduate with mission of protecting human population on distant planets of year 5736. The game field has a shape of sphere, with several enemy landing bases and peaceful citizen colonies connected by roads. Various gun towers should be built (keeping the distance between each other) across the paths in order to prevent alien invasion, but they also might be sold (useful when enemy gets immune to certain damage type...