Say I'm speedrunning Undertale. This usually means you're doing a genocide run, and need to kill a certain number of enemies per section.
Snowdin in particular seems difficult to get the right number of enemies to spawn.
In the Ruins, you can run circles in the room right under the candy.
Hotland is quite easy to get the right number of kills just by taking the usual path.
The Core has the final bridge before the Mettaton fight.
I can't figure out Snowdin. Where should I walk to maximize the number of encounters?