So... good job on this game! I have a few thoughts:
- Nice animations! I really like the death animation, and how you respawn. The foreground/background switch is kind of abrupt -- could you made it fade into the background over a short interval of time? I think it'd really improve the game.
- Transitioning between stages isn't super smooth. It might be better if you made you start at the same height as the last level on the left. Maybe you could add a transition animation between levels?
- Even if you don't do those two, you should at least make it so you start on the floor -- it'd be more smooth...
- I like the humor in the game -- funny messages!
- Could you add sound effects? I think it'd improve the game, too...
You should add more content and make it a full game! Good luck coding!