Super Mario Bros. 3Mix is a large-scale hack that changes and adds lots of features to Super Mario Bros. 3, and pays homage to many past and (relative) FUTURE Mario titles, while attempting to remain faithful in spirit to the look and feel of Super Mario Bros. 3.

All new levels (and a few “remixed” Mario 3 levels somewhere in there)
Many new songs added from other Mario games (kept some SMB3 classics!)
Play as Mario, Luigi, or Toad (cosmetic only) in any configuration
New power-ups (Penguin replaces Frog, Carrot replaces Tanooki)
Star Coins (which are used to unlock portions of the game!)
Ability to re-enter past worlds (with level completion intact!)
Ability to re-enter past levels (to get all of your Star Coins)
Alternate exits in some levels
Ability to save progress
Many new enemies, typically some special ones for the world theme
All new bosses (many are “remixes” of bosses from other Mario games)
All kinds of gameplay changes to meet the theme of a level/world!