New Super Mario Bros. is a side-scrolling video game. While the game is seen in 2D, most of the characters and objects are 3D polygonal renderings on 2D backgrounds, resulting in a 2.5D effect that visually simulates 3D computer graphics. The player can play as either Mario, or his younger brother, Luigi. Similar to previous Mario games, Mario and Luigi can jump, crouch, collect coins, stomp on enemies, and break open blocks.[3][4] Moves from 3D Mario games appear for the first time in 2D Mario games in New Super Mario Bros., including the ground pound, triple jump, and wall jump. Enemies from previous games, such as Boos, are also reintroduced, while various other new enemies are introduced.
Between eight and twelve levels are available in each of the eight worlds in New Super Mario Bros., which are shown on the Nintendo DS's bottom touch screen while the player is viewing the world map in the game. The map of the currently selected world appears on the top screen, which is used to navigate between the world's levels. The goal of each level is to reach a black flag at the end of the level. At the end of each world, a different boss must be defeated before proceeding to the next world. There are six power-ups available in New Super Mario Bros.; the game allows the player to store an extra power-up when he is already using one, a feature carried over from Super Mario World. Three power-ups from Super Mario Bros. return in the game: the Super Mushroom makes Mario grow in size, the Fire Flower lets Mario throw fireballs, and the Starman makes Mario temporarily invincible. Three more power-ups are introduced in New Super Mario Bros.: the Blue Koopa Shell lets Mario withdraw into a shell to protect himself and perform a "shell dash" attack. He also swims faster when in this form. The Mega Mushroom grows Mario to an incredible size, where he can destroy everything in his path, and the Mini-Mushroom causes Mario to shrink, allowing him to enter tiny passageways. Mini Mario is so light that he can run on water and jump extremely high.
The multiplayer mode in New Super Mario Bros. features two players against each other as they play as Mario and Luigi in one of five stages, in which they try to be the first to obtain a preset number of stars. Both players can attack each other in an attempt to steal the other player's stars. Jumping on the opponent's character will make them lose one star while performing a ground pound will lose them three. In addition, some minigames previously available in Super Mario 64 DS have returned with 3D graphics and now offer multiplayer options for added replay value. The minigames are divided into four categories: Action, Puzzle, Table and Variety. New Super Mario Bros. features eighteen minigames for single players and ten minigames for multiple players.