Use the cannons to pop the metal bloons, you dont have to waste money on buying pineapples plus the cannons have great AoE upgraded fully. Beat most of the maps with just freeze towers and cannons.
Man after beating the lvls I was looking at some of the save contraptions and I have to say some of you guys are just creative I would of never thought of half of them.
I hate this game. Why make this a card challenge it might look better than some of the games but graphics are still not good. And all the guns just suck not enough damage might as well run through the whole game with the pistol.
 "Bloons Tower Defense 3"){kind=icon}
 "Orchestrated Death"){kind=icon}
 "Fantastic Contraption"){kind=icon}
 "Monster Basement 2"){kind=icon}
 "Ultimate Defense 2"){kind=icon}
 "Doeo"){kind=icon}
 "Thing-Thing 4"){kind=icon}
 "The Visitor"){kind=icon}
 "TwoThree"){kind=icon}