Big pile of steaming crap.
I've seen these types of RPG attempts in flash and this one sucks pretty bad. And just to prove that I'm not bitching because I lost, when you win it says:
"You win! Player!! Yahoo!
Anyways credits!
Mario sprites edited by
Cyberwolf
Dark yoshi by me"
You announce that the game is hard at the beginning but it's not really hard, just a matter of patience. When Mario heals, it restores 10,000 HP and Dark Yoshi has five attacks, 3 of which takes exactly 10,000 HP (seriously?). So basically, you just heal until he uses a weaker attack and you regain HP, then when you get high HP you launch an assault until the HP drops, then you repeat the process. It seems that Mario's fire attack did the most damage, almost 4500 while his limit break "All out assualt" did the much less damage (why?).
What you should do is come up with more solid mathematics for your HP and damage system. Don't make the attacks do as much as you heal. You don't need two different types of MP. Make Mario's heal more effective but with less uses. And nobody enjoys a painfully hard or long battle. Maybe have a difficulty setting for those who do.
Otherwise, the code seemed pretty good. The flash acted predictable and I didn't really see any major bugs.