Thread:Rewet6/@comment-31463759-20170306214834/@comment-27701762-20170307220329

Your completely arbitrary differentiation isn't useful. Practically every room in the game is unique, and thus can be justified as a different area by pointing to what makes each room different.

Meanwhile, we've already brought forth perfectly reasonable criteria for judging Hotland and the CORE to be the same area. Ignoring those points doesn't make them go away.

But moreover, we can add other similarities to the two areas: the fact that the protagonist encounters the same puzzles in the two areas: lasers, the shooting puzzles, and flipping switches; the fact that the CORE is explicitly designated as being within Hotland in the game's dialogue; the fact that the "regional antagonist" after Undyne is Mettaton, who tracks the protagonist beginning in Hotland and ending in the CORE, in the same vein as Toriel is continually present in the Ruins, Papyrus is continually present in Snowdin, and Undyne is continually present in Waterfall.