here's an easy way to beat timed levels: take it down to one enemie, like a tower, and DONT KILL IT! It will stay there, floating and/or shooting at you, you can easily evade it while the timer counts down, and no other enemies will spawn. However, if you need MONEY MONEY MONEY, I suggest you do it normally or play another level...
 "Endless War 3"){kind=icon}
 "Epic Combo!"){kind=icon}
 "Run"){kind=icon}
 "The World's Hardest Game #2"){kind=icon}
 "WalkRight"){kind=icon}
 "Hanger"){kind=icon}
 "The Birdinator"){kind=icon}
 "Sydney Shark"){kind=icon}
 "Multitask"){kind=icon}
 "Death vs. Monstars"){kind=icon}
 "You Have To Burn The Rope"){kind=icon}
 "Thanks Tanks!"){kind=icon}
 "Black Navy War"){kind=icon}