Warp (2in1)

Warp is a reconstruction of the level of the same name in vanilla Super Monkey Ball 2. It is the 19th stage of Expert for 2in1 and the first mandatory difficulty-of-10 stage (the actual first 10 can be skipped with the warp goals in Tiers).

Description
The stage is a huge block with three increasingly larger sections removed: One near the bottom right, one in the middle left, and one in the top right. Not counting the starting area (which is located in the bottom right), the stage curves downwards towards the edges. With each hairpin turn, the stage gradually gets steeper. There are also bumpers that line the inner-most edges of the removed sections (as well as bananas in between these bumpers). The blue goal is placed in the top left of the stage, while there is an additional path that has bumpers lining the left and right sides that leads to a green goal.

Goal tutorial
The first thing you'll want to acknowledge is that rolling through the tilted catwalks with bumpers is made much easier if you use diagonals, as well as pay attention to the line of checkers you're on.

Approach the first tilted catwalk, and try to remain vertically within the fourth to seventh column of checkers from the right. To move through the path, hold up right, making sure to switch to up for a split second if you start to get close to the bumpers. If you find yourself slipping to the left, hold down right, this will cause the camera to rotate to the right, allowing you to correct yourself. In this first tilted catwalk, you only have to pass six bumpers.

In the next tilted catwalk that tilts to the right instead, it's steeper and requires you to pass eight bumpers. Again, use up-left to move forward and down-left to stop if you start to slip, and try to remain in the fourth to sixth column of checkers from the left.

The third and final tilted catwalk requires you to pass ten bumpers and tilts as far as 30 degrees, and this section of the stage is what probably causes more GameCube controller-related accidents than any other stage in the entirety of Expert in the vanilla SMB2. The strategy is the same, except it's crucial that you try to remain in the fourth to fifth line of checkers from the right. If you're beyond the eight row of checkers from the right, you're most likely dead. Hit any of the bumpers and you're also most likely that. Otherwise, carefully roll towards the goal. It's placed at an angle, use what you've learned to align yourself with it and give your thumbs a rest.

If you want an even bigger challenge, after passing the third set of bumpers, move up the slippery floor and head towards the small section of the stage bends down in the other direction. There is a green goal on the other side, however there are also bumpers lining the left and right sides of this path, with only a little bit of extra space for the ball between these rows of bumpers. Should you hit any of these, you'll probably be spit out between the bumpers and have to do the entire stage over again. Otherwise, carefully line yourself up with the green goal, slowly inch forward, and at the halfway point, gravity will do the rest and you'll drop into the green goal. Unfortunately, the only stage this particular goal skips is a bonus stage, but it's still there for RTA runs as well as score ILs.

Differences from vanilla
The only difference mechanically is the starting position is placed on the large rectangular part of the stage and facing diagonally in a north-west direction. The floor, visually, has been given an overlay to make it slightly more obvious where the safe areas on the catwalks are. The steeper the stage gets, the more red the floor becomes.

Trivia

 * This stage was originally intended to be Expert 35, alongside its other World 8 friends, and a version of this stage in Arctic does indeed exist. However, Warp was kicked out of the Arctic saga because it didn't fit in with the given theme of stages (for all stages to focus around mechanical parts), and it additionally isn't capable of supporting reflections. And because it doesn't appear in 2in1's debug stages, the Arctic version of Warp remains unreleased today.
 * Unfortunately, instead of being put later in the game like it should have been, it was put into the Underwater stages (to reference just how many Underwater stages used bumpers in SMB1), and, while it looks fine, a survey determined it to be the hardest Expert stage aside from Entangled Path (which was overhauled in SMB2in1), as well as most players believing it should be an Expert Extra stage, which means this stage is a gigantic difficulty spike for 2in1 just as Exam-C is for vanilla SMB1. The saving grace is that it's easy to get consistent at, unlike something like Air Hockey.