New Super Mario Bros. is a 2D side-scrolling platformer game. Like previous 2D entries in the Super Mario series, the player controls either Mario or Luigi, and must traverse through levels to reach the flagpole at the end of each one. Mario can access a variety of forms based on power-ups found throughout the world. Familiar enemies, such as Koopa Troopas and Goombas return. The game introduces several elements not previously seen in 2D Mario games, including a flexible camera zoom, physics engine, limited voice acting, and moves introduced in 3D Mario games, such as the wall jump and ground pound. The DS Touch Screen also allows for the player to hold a power-up for later usage.
Aside from the classic Super Mushroom and Fire Flower, Mario has access to a series of new power-ups: the Mini Mushroom makes Mario smaller, allowing him to jump higher, run on water, and access tiny pipes, at the cost of his strength and durability; the Blue Shell allows Mario additional durability and the ability to dash in a spinning spell dash; the Mega Mushroom temporarily makes Mario gigantic, allowing him to stomp his way through most obstacles and enemies.
The game features two different forms of multiplayer, which is conducted by way of wireless connectivity.
This mode is restricted to 2 players. One plays Mario, the other plays Luigi. They run around one of five wrapping, side-scrolling levels. The objective is to gain an amount of stars, which appear randomly. The bottom screen displays a "map" that shows where the two players are, and where the star is. This number depends on what you set it to before the game. Players can jump on each other, or hit each other with power-ups to knock the stars out of each other. They can also collect coins. For every 8 coins gathered, a power-up will appear near that player.
The game also features many original minigames from Super Mario 64 DS. They can be played alone, or with up to 4 players. These vary from card games like a primitive form of poker, to action games, like shooting snowballs at each other. The games from Super Mario 64 DS are also reworked to be more competitive and feature multiple players.
Mario and Princess Peach are taking a stroll one day. Suddenly, a mysterious gray storm cloud strikes Peach's Castle. As Mario runs to the castle, Bowser Jr. kidnaps Peach. Mario quickly chases after Bowser Jr., following him to a castle where he fights Bowser. The plumber defeats the Koopa King by dropping him into a moat of lava, leaving behind only a skeleton, but Bowser Jr. escapes with Peach.
Mario follows Bowser Jr. through several worlds, eventually cornering the Koopa prince. Bowser Jr. revives his father, and the two fight against Mario. Eventually, Mario prevails, defeating both Bowser and his son, and rescues Peach from captivity. Peach rewards him with a kiss, leading to the credits.
After the credits, Bowser Jr. can be seen dragging his unconscious father away, temporarily breaking the fourth wall by growling at the player.
- New Super Mario Bros. is the first new classic side-scrolling Mario game since the SNES and Super Mario World.
- Luigi can be played in the single player story by holding L + R when selecting a save file.