New coins are minted after every 2 or 3 moves, depending on difficulty. You can keep tabs on them at the bottom of the screen (Red bar - 1 move, Yellow bar - 2 moves, Green bar - 3 or more moves) and strategize accordingly. If a column of coins reaches the top of the screen, you'll get a warning, the coins will flash, and you will need to remove enough coins to get back to a safe height. If you can't make a move, your game will end!
What’s the catch? None, really. Cash back apps act as affiliates for many online merchants, which means that whenever you make a purchase through one of the apps, they get a small commission — but then, they give you a portion of that commission as “cash back”. For example, if I buy a pair of Nike shoes through the Ebates app (or website) and spend $75, Ebates may get a $10 commission but then they’ll pass $7 back to me. It’s basically a way to get sale prices on stuff that isn’t on sale!