Mario Shell Defense - 2.0

You play as Mario, who's desperately trying to defend himself against an onslaught of Koopa shells! Use the left/right arrow keys to run, the space bar to jump, and the "e" button to shoot fireballs! Shoot fireballs at the shells to destroy them. If you get hit by a shell, it's game over. Only tested on Win XP so far, but as far as I know it's cross-platform compatible. Please leave your comments and criticism, and feel free to poke around through the code and comment on how I could be doing things better.

-Added in this version: Mario is now animated, and can jump on shells to destroy them and get points!
-Fixed: File name issues that caused errors in Linux and Mac OS. Also tweaked some code to fix errors for Linux users.
-To do: Maybe give Mario a health bar? Perhaps make him shrink when hit the first time, then dying after the second hit (like the original Mario platformers). I'm just sort of winging this, since this project is really just a learning experience for me. Suggestions welcome!