Æther is a hack that's so involved, that even the basics are pretty different from the standard Mario World fare.
Eszett here is able to sprint by holding Y, but transitions into a jog by releasing it - a middle speed that's stamina efficient. She can also alter her regular jump into a High Hop by turning around while jumping, or a Long Leap by duck jumping with enough p-speed. The R button is also a dedicated attacking button. It has plenty of other uses but if you use it while ducking, Eszett can go into a slide (even on flat ground).
For more info on the hack:
Smwcentral:
https://smwc.me/1477512
Twitter:
https://twitter.com/_Dappertron_
Programming is courtesy of Maarfy, while I did the animations and art.