Normally in a Cave Story remix I don't like the addition of piano, because many of them substitute too many or even ALL the notes with piano. However, for this song you did great, because you captured the main emotion that was to be displayed in the core. If you need to know what a regular emotion coming out of there would feel, think of this: The first time you go in there, unless you ruin it for yourself and look in a guide firsthand, Curly sacrifices herself for you but you can't do anything about it. You start to walk away, guilt wracking your conscience. As you go past that blast door, you think to yourself why you didn't save her, COULDN'T save her. Then this music comes on. Think of how that'd feel.