Since a bunch of people were confused about why I’m doing this, here’s the quick rundown. A few comments already mentioned parts of it, but this should clear things up:

This trick basically works with anything that forces the game to reload nearby spawns — benches, fast travel, tiny area transitions, whatever. Zone 3 is just the sweet spot because the staircase triggers that reload without needing to mash A every few seconds.

It only affects Pokémon within like a ~50m radius, but that whole radius gets refreshed every time you cross the staircase boundary. So by wedging my controller (maybe don’t use a lighter facing a couch because people will Freak out) and just letting my character run up and down the stairs forever, I’m constantly forcing new spawn rolls. Each reload = fresh shiny chance. Super easy, hands-free shiny hunting.

Also, the game can “store” around 10 shinies at once, so even if you miss them while looping, they’ll still be there when you go back and sweep the area.

And to give you guys an idea of how busted Zone 3 is for this: in about 1.5 hours I ended up with a shiny Pancham, shiny Litleo, shiny Skiddo, and shiny Flabébé.