btw, found easter egg after completing each level about a thousand times... just a hint, it is in the main menu, not in the game... (if you run out of ideas, just click randomly.... That's how i got it^^)
i got the badge without playing it more than 2 or 3 levels... Buy for each floor an elevator and at first one machine gune and two cheapest... later you buy rocket launcher and laser.... and upgrade them... buy everything you can after each day... you dont need to play along during the wave after day 4 or 5..
 "Ultimate Crab Battle"){kind=icon}
 "Dark Cut 3"){kind=icon}
 "Castle Crashing \"The Beard\""){kind=icon}
 "Dark Cut 2"){kind=icon}
 "Canabalt"){kind=icon}
 "Little Wheel"){kind=icon}
 "Fishing Girl"){kind=icon}
 "Liquid Measure"){kind=icon}
 "Plazma Burst: Forward to the past"){kind=icon}
 "The Next Floor"){kind=icon}
 "This is the Only Level"){kind=icon}
 "Pyro II"){kind=icon}
 "Raft Wars"){kind=icon}
 "Medieval Rampage"){kind=icon}
 "Gravitee 2"){kind=icon}
 "GOBTRON"){kind=icon}
 "Red Remover"){kind=icon}