Your mission in this tactical slidescrolling shooter free online games to take the role of a Marine and blast enemies and upgrade your warrior as you try to save the planet from impending doom. Try to find the time machine to prevent the coming of thousands of alien usurpers. Use wasd keys to move around and use your mouse to aim and fire. Use number keys to change weapons. Press "G" KEY to throw a grenade. Press "E" key to use items. Use "Z" key for time warp . Good luck!