When the portal to another dimension opens, it's up to you to stop the alien invasion in a free tower defense game online. Explore the level layout and build towers to effectively stop the monster waves. Place new defences during the fight once you have earned enough money to afford them. Read the description of every type of both turrets and monsters in order to succeed. Vivid soundtrack will help you tune to the pace and complete all levels of this free online action game. If you are a fan of defense games, browse the site for more arcade games for boys, starting with the sequel to this hit!