Needs work...
This was decent. It would be better if you used SMB3 or SMWorld sprites. And like everyone else said, the background has to move. Its a must for these games. Make original traps that would make since in the Mario world. Example: Mario always uses his green pipes. Well if you happen to land on a green pipe at the perfect time, you go down it and lose.
On the other hands, put coins in the air too. While Mario is soaring through the air, put coins in the air. That way you can use the coins as a way of upgrading either the catapult or the character..
One more thing that I would love to see out of all catapult games: more than one character. Another (and last) example: Mario is your well rounded character, Luigi is long thus he can catch more coins, Princecess stays in the air longer, Toad bounces higher, and so on.
Sorry that this is rather long. I like catapult games, but all of them need work. I would like to see a version two of this!