Arthropod (2in1)

Arthropod is a reconstruction of the level of the same name in vanilla Super Monkey Ball 2. It is the 30th and final Advanced stage.

Description
The player starts on a long rectangular platform that leads to a grand set piece, consisting of a robotic insect with six legs and cone feet constantly walking on an enormous hollow drum, rolling it counterclockwise like a treadmill. The goal hangs on the back edge of this cylinder, starting at the top, gradually rotating to the bottom and then back up. It takes 30 seconds for this drum to finish a rotation.

Goal tutorial
The player can choose to immediately roll onto the drum and try to avoid the arthropod. The easiest way to beat the stage is to wait 20 seconds on the safe rectangle, then roll towards the goal as it completely points upright, making sure not to get crushed by the arthropod's feet along the way. In order to get faster times, the player can carefully roll off of the drum around the 23 second mark, and free fall into the goal while it's at the bottom. This will require good air control. It's also possible to drop onto the underside of this drum, and roll towards the goal while it's upside down instead. Note that the underside of the drum is not completely flat: It's slightly sloped outwards, so again, you need good air control to carefully to stick the landing.

Differences from vanilla
The long rectangle platform the player starts on here is a traditional Super Monkey Ball 2 starting bridge. There are also no bananas around the ring, instead they rest on the two corners of the starting platform.

The drum the arthropod walks on is one large drum, much like it's debug counterpart in the vanilla SMB2 files (IDs 80 and 192). In the final release, however, the drum was split into five parts, with no way to roll around on the underside. This was presumably to spice the level up for it being the final Advanced stage. Unfortunately, these gaps ended up adding too much difficulty to the stage. The width of these gaps are 1.5 units apart, with the ball itself being 1 unit in diameter. The width of each of the drums are 4 units wide. The problem is because these gaps are on cylinders that are constantly rotating, this makes crossing them wildly inconsistent and frustrating: There's barely enough room to make it past each of these gaps without rushing, and if you do rush, it's easy to overshoot and slip off the drums entirely, and trying to brake can result in the ball getting caught into one of the gaps and falling. Even if the player makes it to the final drum, they still have to try not to get crushed by the back-most leg of the arthropod.

Unfortunately, this particular stage in the vanilla games is most certainly responsible for more shouted profanity, pulled hairs, thrown controllers, snapped game discs, and kicked dogs than anything else in the entire game, because it's located in World 4, as well as being the final Advanced level. A survey determined Arthropod to belong in Expert Extra due to the extreme intensity of reaching the goal. To put this into perspective, the only Expert Extra levels that were ranked harder than Arthropod in this survey were Giant Swing (and only by a few decimals), Construction, and Train Worm. Needless to say, these gaps were completely decimated in SMB2in1 to make the stage more fitting for Advanced, as by the time it was made, all of the Expert, Expert Extra, and Master stages were firmly decided on.

Glitches
This stage has spasmodic framerate drops if it's played on console, specifically on Homebrew/Nintendont. This is because all of the parts of the arthropod are casting a shadow onto the drum. As it turns out, if there are too many objects casting a shadow onto a surface, it'll cause the game to slowdown when played on console. This is also why in both versions of Arthropod in the vanilla games, the arthropod doesn't cast any shadow onto the drums at all. This limitation is also why Totalitarianism is notoriously hard to replace: Stage-specific shadow effects were directly hardcoded into the slots (015 and 229) for Totalitarianism and rely on a specific object in the .gmas for those slots (the 7th object in 015 and the 53rd object in 229) to give the stage shadows, as real-time shadows like what is seen on Hoppers and Mad Rings also causes Totalitarianism to have terrible slowdown. (In SMB2in1, Totalitarianism lacks shadows entirely due to this.)

The other stages in 2in1 that are known to lag for similar reasons are Melting Pot and Vortex.