Mario R3mix is out! Go play it! http://www.newgrounds.com /portal/view/612706
In Mario Remix: Boss Edition you're up against 35 famous and original bosses from past series. It also includes an item system and original minigames.
A long time ago I made Mario Remix. Ever since then I've been wanting to do another Mario crossover game. Well, I've finally gotten around to doing it. I've always loved a good boss fight. Enjoy!
Big thanks to gargle-greg for making a walkthrough. Check it out:
EDIT: Almost all bosses require 8-12 hits to kill. Standing on them after they recover will hurt you. Use the item shop to get mushrooms so you don't die in 1 hit.