Sideways crouch roll
Sideways crouch rolling is a movement technique that can be used to gain more rolling speed than would otherwise be possible. It is performed by crouching while Mario’s rotation differs from the direction of his horizontal velocity, then rolling. Sideways crouching is most easily performed on ice, but it is also possible after landing from a jump, roll cancel vector, or falling.
Explanation
When a crouch roll is initiated, the game increases Mario’s velocity in the direction he is facing to 20 u/fr if it is lower than that, while maintaining all of his speed perpendicular to the direction he is facing. This means that if Mario is not facing in the same direction as his velocity, he ends up with more speed during the roll than he would otherwise. In order to get the largest speed boost, Mario should crouch while facing 90 degrees away from his velocity direction, so that he has no velocity in the direction he is facing and therefore gets a full 20 u/fr velocity increase in this direction. However, crouch rolling at this angle redirects Mario’s velocity significantly to the side, and facing closer to Mario’s velocity direction results in a less drastic redirection, albeit granting less speed.
Even when rolling as soon as possible after the crouch, Mario experiences one frame of speed decay from crouching. His velocity in the direction he is facing decreases by 5% (1.5% on ice), and his velocity perpendicular to this direction decreases by 7% (2.5% on ice). Unless Mario is on ice or the joystick is neutral, his sideways velocity is capped at half of his forward velocity, which is likely near zero when performing a sideways crouch roll. Therefore, if Mario is not on ice, the player must release the joystick upon crouching.
Setup
Setting up a sideways crouch roll on ice is simple because holding to the side turns Mario while having little effect on the direction he is moving on. However, it is more difficult to separate Mario’s rotation from his velocity direction on land. If Mario is facing sideways in a jump, fall, or roll cancel vector and runs upon landing, Mario’s velocity direction shifts to his facing direction over the course of a few frames. On the first such frame, a sideways crouch is somewhat effective in terms of gaining speed but redirects Mario’s velocity drastically from his velocity direction during the jump. A more effective and adjustable option is to perform a moving pivot upon landing. This results in 1.4 u/fr speed loss upon landing, but Mario’s rotation can be freely adjusted during the pivot while continuing to move in the same direction as he was at the end of the jump and not losing any additional speed. If the direction Mario is facing before the pivot is desirable, the player can even choose to crouch on the frame the pivot would have started on, resulting in just as early of a crouch roll after landing as usual. Sideways crouch rolls from moving pivots are challenging to perform RTA but can be carefully controlled to optimize TASes.
Examples
Mario performs a max speed single jump, so his speed is capped at 24 u/fr upon landing, then gets reduced by 1.4 u/fr to set up the pivot. Mario uses the pivot to rotate so that he is facing 90 degrees from his velocity direction. When he crouches, all his velocity (22.6 u/fr) is perpendicular to his rotation. The player holds neutral to prevent all of Mario’s speed from being lost, but still a 7% decay is applied to this velocity, yielding a velocity of 21 u/fr in this direction. The player immediately initiates a roll, so Mario’s velocity in the direction he is facing is bumped up all the way to 20 u/fr from 0 u/fr. These velocity components yield total velocity of just over 29 u/fr, which usually takes several rolls to reach, and he is now traveling in a direction that differs from his previous velocity direction by around 44 degrees.
If Mario is lands from a roll cancel vector with 30 u/fr speed, then loses 1.4 u/fr speed from entering a moving pivot, then he can attain up to 33.3 u/fr speed from a sideways crouch roll.