Let's see:
A platformer with coins to collect and health items and powerups. Player must collect all coins before exit door is opened and must go to that exit.
However, there's a twist: after collecting certain number of coins, level will be darker and enemies will appear. Some only deal 1 or 2 hit points damage while some could one shot player. The less coins to be collected, the more enemies will appear and the darker level will be.