Beware Planet Earth! Demo

Description
Heed the warning from the red planet, Earthlings! The Martians are about to strike our beloved planet to take our single most valuable resource: cows! Protect Barney\'s ladies in this colorful and whimsical tower defense game!
Features:

Full Story Mode (46 levels over 4 seasons), plus 18 bonus challenges!
Intense action! Grab your Zapper to attack the Martians and overpower your machines!
20 wacky machines, from the classic defense tower to the Helicowpter!
Over 20 quirky Martians, from the Metalhead to the Mad Scientist to the Ninja!
25 Achievements!
Cows!