New Super Mario Bros. is a side-scrolling video game. While it 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.[1][2] The player can play as either Mario, or his brother, Luigi. Similar to previous Mario games, Mario or Luigi can collect coins, stomp on enemies, and break open blocks.[3][4] Moves from 3D Mario games reappear in New Super Mario Bros., including the ground pound, triple jump, and wall jump.[4] Enemies from previous games, such as Boos, are also reintroduced.[5]

Ten levels are available in each of eight worlds, which are shown in the Nintendo DS's bottom touchscreen while viewing the world map.[6][7] The map of the currently selected world appears in the top screen, which is used to navigate between the world's levels.[7] The goal of each level is to reach a black flag at the end of the level. At the end of each world, a boss must be defeated before proceeding to the next world.[6] 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: 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 "shell dash" attack, the Mega Mushroom grows Mario to an incredible size, and the Mini-Mushroom makes Mario very small.[6][8]

The game's multiplayer mode pits two players against each other as they play as Mario and Luigi in one of five stages, trying to be the first to obtain a preset number of stars. Both players can attack each other in attempts to steal the other player's stars. Jumping on the opponent's character will make them