For starters verity is missing right now maybe try adding different size platforms and different types of platforms and enemies stuff like that. Besides that instead of the timer you could go with a goal based approach like collect 10 cookies move down to deliver them then collect 20 cookies. The timer is also fine but I could just get one cookie and still win the game. I think the falling has potential, maybe add some way the player can fall because of the environment and has to find a way to save themselves.