What you’re describing is the Backwards Long Jump. Due to developer oversight, Mario doesn’t have a maximum speed going in reverse. Mario can long jump repeatedly in reverse against stairs and similar collision, causing him to build up a ridiculous amount of speed until he’s going so fast that he bypasses the wall collision. He’s on one side of the wall on one frame, and on the other side by the next. Since the game only checks his collision every 4 frames, he goes right through.
![Speed run [Last Place Comics]](https://lemmy.world/pictrs/image/6f759a2b-e344-4438-bb36-800cdef8a20c.jpeg){kind=link}
What you’re describing is the Backwards Long Jump. Due to developer oversight, Mario doesn’t have a maximum speed going in reverse. Mario can long jump repeatedly in reverse against stairs and similar collision, causing him to build up a ridiculous amount of speed until he’s going so fast that he bypasses the wall collision. He’s on one side of the wall on one frame, and on the other side by the next. Since the game only checks his collision every 4 frames, he goes right through.