We have created a fairly functional game. We have a score, cool animations, collision detection, and levels in our game. After playing it, what would be the first thing you would improve? Let your friend play it. What did he/she think? Try to come up with a change that improves the game based on your experience playing it.
In addition, we designed our game so that it would be easy to add new rewards, enemies, and platforms. Add one of each to the game and add your own twist to them. For example, you could create a super cupcake that is worth five points but only lasts a short time. This will require the player to make some quick, meaningful decisions during the game.