Click (I prefer to hold it down for the bosses!!!) the aliens to kill them. try to get to the finial level which is level 20. (each level is 20 seconds long.) Alien Tiers: Alien Types: Green - Normal Round - Normal Blue - Speedy Red Round - Normal Duplicator Red - Insane Spikey - Takes a few secs to die Orange - Hider Invisible Red Spikey - Just moves Purple - Boss Boss - Just moves Yellow - Final Boss Final Boss - Just moves DLC - Combo Stars have been removed because of a glitch they caused.
