According to director Masahiro Sakurai, Smash Run pits four players against each other in a cross between a platforming marathon and standard Super Smash Bros. combat. The initial section of each game will see players racing through a labyrinthine dungeon stocked with power ups where they must use each character's individual skills to navigate obstacles and defeat AI-controlled enemies. Players will plumb these depths for five minutes, then they face off in combat, using the power ups they have collected.
Sakurai fails to mention how many stages will be available for Smash Run, though the map shown during the broadcast appeared quite large and complex. Smash Mode is exclusive to the Nintendo 3DS Super Smash Bros., though Sakurai made no mention of what might takes its place in the Wii U version of the game.
Edit: Originally this piece described the new mode as "Smash Mode" when it is actually called "Smash Run." We apologize for any confusion and have amended the error.