This looks like a good place to ask HN: I've started with a solved cube, then turned 2 sides sharing an edge, alternatively (same direction) expecting the cube to get messed up but then returning to its solved state. It never got solved! Maybe i didn't do it enough (i did it hundreds of times i think). Has anyone got an explanation?
It takes something like 60 turns or so in my experience. you probably messed up while doing it.