The changes range from significant to more minor, but the biggest alteration comes in the form of a new stage. With its previous update, the development team added 'Temple: M', an abridged version of the larger (Hyrule) Temple stage found in Super Smash Bros. Melee. With the 2.1 update the team decided to bring the Temple back in its complete form, but also gave Temple: M a makeover. Themed to The Legend of Zelda: Skyward Sword, the small stage features a moving Skyloft as a background, complete with soaring Loftwings.
Other alterations include a variety of fixes and tweaks to characters like Ganondorf, Sonic, Lucario (who was completely remade in M 2.0), Charizard (who will eventually be joined by Bulbasaur and Squirtle) and R.O.B. Tweaks also extend to some of the smallest details imaginable, including AI routines, aesthetic details on stages and the character select screen, and plenty more. This is by no means as comprehensive an update as M 2.0, but there will be plenty here that enthusiasts will notice, particularly if their main character has been adjusted.