Making it easy to accidentally spend money with no confirmation or ability to undo or refund the action.
"Tower upgrades can be purchased for real money, which is an option presented alongside all other upgrade information during gameplay"
"It only takes a few taps to buy something, especially if you have your card details saved. Do not let a child get their hands on this if the parent has bought something before; it only takes 2-3 taps."
"When in crunch for events you may wind up spending gems"
"Some buttons are placed over other buttons when pop ups are dismissed, which lead to the shop. Pop ups for purchasing packs with real money pop up with the “purchase button” over where you would normally tap to confirm the action you were actually trying to do."
"actually it's more about accidentially spending in game currency"
"There is no confirmation when selecting Premium currency vs ingame currency to buy a character or cosmetic, premium is selected by default if enough is on the account, making it easy to accidently spend Premium when you mend to spent free currency"