Hyperspeed Turnaround
Hyperspeed Turn Around (HSTA)[1] is a hyperspeed glitch to build up speed.
Execution
It uses the "turning around" action, which happens when you're walking at >=16 speed and you hold back on the joystick. This action will build speed on 0x13 slopes with a normal.y in the range 0.9848077-0.9961947. This doesn't work on slide levels.
This is like C^ sliding, with two distinctions:
You can hit walls/OoB without bonking or losing your speed (forward or backward)
You have tighter normal.y restrictions since you can't be on a slide.
It's currently not thought to be possible to get into this action with negative speed, and you can't change from positive to negative while in the action.
Going neutral while in this state will put mario in skidding, which is the C^ slide action. From here you can press B to go into move punching, or wait one frame and move the joystick to go into walking.