NK should implement tile markers that players can put down on unbeaten tiles to indicate if they are harder than their rating would imply. Unless this problem is really a ploy to get players to use more bloon stones on "trap" tiles, such a feature would let players remember which tiles are too hard, and allow NK to rebalance tiles that are marked if they feel so inclined.
(fixed drunken grammar and syntax errors)
NK just implement tile markers that players can put down on unbeaten tiles to indicate if they are harder than their rating would imply. Unless, this problem is already a ploy to get players to use more bloon stones on "trap" tiles, such a feature would let players to remember which tiles are too hard, and allow NK to rebalance tiles that are marked if they feel so inclined.
 "Bloons Monkey City"){kind=icon}
 "Vault Rush"){kind=icon}