Your mission in this strategy Tower Defense game is to install a setup of defensive towers including laser towers (and even a Robocop tower), as you attempt to defeat the Zykon alien armies. Enemies come from the left and bottom of the map and exit at the right side. Use YOUR MOUSE to place towers. You can use TAB KEY to cycle through towers and "U" KEY to upgrade selected tower. You can speed up the game by clicking the 1X button. The game may lag a bit in 4X. Have fun!