>>21314750Basically a challenge run. The rules vary person to person, but it comes down to three points:
1) If a Pokemon faints, it's considered dead and you can't use it anymore.
2) You can only catch the first Pokemon you see on each route. That's the only catch you get there, and if you fuck it up, tough luck.
3) Nickname your Pokemon so you get more attached to them.
Some games are better for it than others. I'd recommend games with a larger roster so you won't run into duplicates constantly.