I will never again look down on "magnet" upgrades. Collecting money was annoying in this game, as was the penguins AI: they locked on to a seemingly random turtle, ignoring the one right next to them and get stuck on a wall for half the stage.
OK, that last badge was a real cookie. Challenge 15 was all about a lucky starting hand, more or less, but I got lucky and won on my 3rd or 4th try. I finished challenge 20 with the Shotgun, after trying everything else, including Yog-Sothoth, Raid, Tommygun, and everything else in between. I suppose it may be a random choice of card.
 "Crush The Castle 2"){kind=icon}
 "Nano Kingdoms"){kind=icon}
 "Vinyl Memories"){kind=icon}
 "Elephant Quest"){kind=icon}
 "Penguin Overlords"){kind=icon}
 "Epic Combo!"){kind=icon}
 "The Necronomicon"){kind=icon}
 "Alice is Dead Episode 3"){kind=icon}
 "Kingdom Rush"){kind=icon}