AFAIK, this is a new tech. Here's how it works:
-I have Mario move into a wall hitbox on the fourth quaterframe of his last sliding frame.
-For ground movement, Mario has no vertical speed. So his horizontal movement happens first, and then the wall collision test happens. This means that the position being tested is at the new position horizontally, but at his previous height vertically. This position is above the wall, so Mario does not get pushed back by it.
-Next, Mario's floor collision test happens. After this he snaps down to the ground. This brings him inside the wall hitbox, but because the wall collision test happened already, he doesn't get pushed away. Since this is the last quarterframe, Mario will start the next frame inside the wall.
-On the next frame, the initial wall collision check (prior to qframe movement) pushes Mario away because he is now inside the wall. This pushes him off the slope and onto the flat ground. The initial floor collision check does not change Mario's height, so Mario is now above the flat ground by about 30 units.
-After this comes the DR check. Because Mario is above flat ground, he is able to DR, and the extra 30 units allows him to reach the star. In fact, it gives him 11 DR frames to reach it, so the h speed I get from the slope (about -80) is enough.
