don't forget to include: 

1. gravity (accelerating upward and downward) 

2. 2 player control with animations for rising & falling 

3. randomly generated clouds - clouds grow and pop 

4. score - negative points for falling off; positive points for jumping on other player - doesn't scroll with camera 

5. respawn after death (wait a second & then jump back up) 

6. camera moves with both players 

7. effect for player collision 

8. no end state! 

9. collision with cloud when you're moving down & then cloud disappears. no collision when moving up 

10. collision jumping on other player only when one player is moving down 

11. bounce off wall collisions! 

12. cloud generator with a maximum limit - clouds don't appear direcly on top of each other