Originally posted by Hobz
if you make the first extra byte over 7F it goes up instead of down, and if you leave the second extra byte empty it teleports back to its spot.
tho I am more curious as to why it doesnt reset all the time.
The first behaviour it's related to the speed being is a signed number: speeds from 0-7F are positive, while speeds from 80-FF are negative. Due to the way the Y axis is set up, positive speeds will actually make a sprite fall while negaive ones will make the sprite go up.
As for the second it's unintended behavior for sure. Extrange behaviours can also happen at high speeds but hey, it's the price to pay when one makes something very customisable.