This game was a little tuff. Undertale!Sans and other Undertale!Sans's Friend are together with these nights! But at the darkness thing, you should Press F to using Flashlights, but watch out of this things, If Flashlight does, it goes away. If not, then it makes jumpscare by you! But Unfortunately, Shadow Sans is not here anymore! Goodluck - Tymek1981 / Tymek1981-Alt
Credit to @Tymek1981-Alt, @MrBrianfyScratch720, and others.