you already know how to play this probably, arrow keys for movement and you battle against Sans: 1 atk, 1 df, surely the easiest enemy.right? and you have for your items: Pie(butterscotch pie),Face Steak(mettaton shaped steak),I.Noodles(instant noodles),L.Hero(legendary hero) 2x, S.Piece (snow piece)3x.
i couldn't find the exact parts of sans voice in the "maybe it's the way you're dressed" audio but i did find one from a random sans fight so thanks @sugiharu1012 on his project called サンズ戦 sans Fight. just know that this is sort of more difficult then the normal sans fight,though not in ways like it's just hard to do, but like just barely possible to dodge 1 gaster blaster perfectly positioned to be practically impossible. I didn't check if it's possible to no-hit the game also,just keep that in mind(probably is but who knows, scratch's touched object event will activate as soon as one pixel touches the object,most high quality games use hitboxes that are smaller then the actual object so that it doesn't feel unfair because reaction time stuff.).