In addition, it features a new art style for in-game menus and allows players to choose certain characters individually when they are only accessible as transformations of other ones in Brawl.

The game's first demo build was released on February 7, 2011, and development continued until December 1, 2015, when the PMDT announced it would cease further development of Project M. The game has received positive comments from reviewers, amassed a player base of over 500,000, surpassed three million downloads, and been played in many professional tournaments.

Players battle in arenas of varying sizes and levels of complexity, controlling characters with a variety of play styles.

The designers' "about" page lists a number of aspects from Melee that they aimed to carry over, including fast-paced gameplay, "flowing, natural movement", a "great deal of control" in the player's movements, a balance of offense and defense—though they favored offense over defense slightly—and a complex system of combo attacks.

[4] Players who own an NTSC Wii can install the game without any software modifications,[5] but they must delete all custom stages created in Brawl because of the way files are stored.

The general consensus among competitive players was that the latter game's developers had reworked the older battling system to better appeal to casual gamers, by making the attacks and movement of the game significantly slower in general and adding a greater degree of randomness, luck, and unpredictability, in contrast to Melee, which has more straightforward, skill-based gameplay.

[11] By the release of the game's second demo in March 2011, the team's goals for the mod had expanded to a total overhaul of Brawl to better match Melee's gameplay mechanics.

[18] Originally as part of an April Fool's Day joke, the PMDT announced that a new "Turbo mode"—inspired by a YouTube video called "Melee Impossible" that showed off powerful combos—would be featured in the upcoming version 3.0.

[19] The designers set up a Turbo Tuesday video series showing off the mode with various characters, such as Mario and Ike, once a week.

[20] The designers added a "Clone Engine" to the game that allowed them to make the character Roy, whose only appearance in the Super Smash Bros. series at the time was in Melee.

[32] According to the team's attorney and business consultant, Ryan Morrison, the decision was not made as a result of a cease-and-desist notice or legal action by Nintendo.

[34] Members of the PMDT later went on to form the game studio Wavedash Games and develop Icons: Combat Arena, a fighting game with similar mechanics to Project M.[35] After Nintendo sent a cease and desist letter to tournament organizer The Big House for their use of the Slippi emulator in their 2020 Melee tournament,[36] Project M's official website was updated for the first time in several years, voicing support for the Smash Bros. community and linking to a mod derived from Project M, called Project+.

[40] Bowser, a character who was generally not considered viable for tournament play in previous games, was given armor and increased attack power and made larger.

[44] Before the project was discontinued, several newcomers were planned for addition, including Knuckles the Echidna from Sonic the Hedgehog, Lyn from Fire Emblem, and Isaac from Golden Sun.

Ryan Rigney of Wired called it the best iteration of Super Smash Bros. and felt that it successfully transforms Brawl into a serious competitive game.

[51] Zach Betka from GamesRadar called the game "beautiful" and enjoyed the presence of "many edits that will make the average Smash fan squeal.

"[44] Prior to its discontinuation, Nintendo's Miiverse Internet forum would apply an automatic ban to those who mentioned Project M on the grounds of it being "criminal content", including the acronym "PM".