|World location||Acorn Plains|
|Players||Mario, Luigi, Blue Toad, Yellow Toad, Mii|
|Enemies||Goomba, Buzzy Beetle, Koopa Troopa, Piranha Plants|
|Previous level||Acorn Plains-1: Acorn Plains Way|
|Next level||Acorn Plains-Tower: Crushing-Cogs Tower, Acorn Plain-S: Blooper's Secret Lair|
|Game(s)||New Super Mario Bros. U|
Tilted Tunnel, or Acorn Plains-2, is the second level of Acorn Plains in New Super Mario Bros. U. It's a primarily underground stage with shifting crystals and slanted pipes. This is the first course to introduce the Fire Flower in this game, as well as the first stage to have a Secret Exit.
The underground course features a variety of slanted pipes, with enemies such as Piranha Plants routinely popping out of them. The crystals that player comes across can teleport the player to a specific point. Players can use ground slopes to slide and destroy enemies.
- Star Coin 1: The first Star Coin of this stage is will on a very clear path through the level. Once you reach the end of a large crystal rock slide, jump to collect the trail of coins after, the Star Coin is nestled in the center of this coin trail.
- Star Coin 2: Once you pass the checkpoint of the stage, you'll see an area with a handful of Piranha Plants and angled pipes. Look out for a lone red shelled Koopa Troopa. Stomp on him and stop the shell. Then throw the shell at a pair of blocks near the bottom of the level. One of the two blocks will sprout a climbable vine that leads to a level subsection. Enter the pip cannon and it will shoot you directly into the Star Coin.
- Star Coin 3: When you come across the Red Ring that reveals Red Coins, you'll come across an area with a sign labelled with a down arrow. Ground pound the area and the rock crystals will move, revealing access to a green pipe that will lead you to the last Star Coin.
Once you reach an area with the red circle, wait for the purple, half circle, crystal rock to turn downwards before returning to the red circle. Once here, you can jump up and over the rock ceiling. This is reminiscent of earlier Mario games, allowing you to bypass the rest of the level by running along the ceiling ledge. However, the secret exit comes from jumping up even further, using the blue rock crystal to push you past the second ceiling. This secret exit will unlock a path to Acorn Plains- Blooper's Secret Lair.