Really, Really easy. Just buy a machine gun, place it in the center of the scheme, upgrade it's range to get the entire screen, and then upgrade it's speed two times. then get an ice tower and do the same. Finally, a gold tower doing the same. End of the game.
 "Fujitsu Defender"){kind=icon}
 "Creeper World Training Sim"){kind=icon}
 "Super Energy Apocalypse : RECYCLED!"){kind=icon}