Boost Mode

Boost Mode is a new feature introduced in New Super Mario Bros. U, where the player with the Wii U GamePad can interact with the game, not by controlling a playable character, but by using the GamePad's touch screen to manipulate the current gameplay.

Boost Mode allows the GamePad player to place platforms in the game to help or hinder the other players. These platforms can be placed by tapping an empty/vacant area on the Touch Screen, and the platforms come in a variety of colors. They include blue spade platforms, red heart platforms, green club platforms, and magenta diamond platforms. The icons on the blocks will disappear over time, and the platform itself soon after. If another player steps on the platform with the icon still on it, it will spit out three coins and a star meter on the GamePad will have a section filled. If the meter fills up all the way, a Boost Star appears; by tapping the Boost Star on the GamePad, they enter into Super Boost Mode, allowing the player to instantly defeat enemies by tapping them for a limited time, similar to a Starman.

Boost Mode is not limited to platforms, however, as the player using Boost Mode can also stun/damage enemies by tapping them, which can be done repeatedly to keep them from attacking.

3-Up Moon Blocks (which will release a 3-Up Moon after being hit and then remain solid) can only be seen on the GamePad player's screen, and become usable for the other players only after being tapped; the block will revert after about 5 seconds, after which it can be hit again.

If the player manages to collect ninety-nine Extra Lives, the Boost Blocks become Mini-Boost Blocks.

Boost Rush
New Super Mario Bros. U features a mode similar to Coin Rush from New Super Mario Bros. 2 called Boost Rush. In Boost Rush, the player will play through a series of levels grouped together in packs, and the objective is to play through autoscrolling levels and collect the most coins, lose the least amount of lives, and make or beat the best time. The speed of the scrolling will increase every ten Coins while Star Coins worth 20 coins each. Unlike Coin Rush, though, the player has limited lives and can gain more by collecting coins or extra lives, although all players share the same lives, and the player using Boost Mode can pop any players in bubbles. When a player is playing Boost Rush, Miis can be seen in the background, supporting the players.

In the Penguin Pack, the Ice Flower is replaced by the Penguin Suit.

Trivia

 * The icons on the blocks spawned via Boost Mode are the same as the four symbols used to sync the Wii U console and GamePad during the system setup.