Right from the start -- thank you for lowering the volume to not blow our ears out! It is such a small detail, but it matters!!
I love the victory tune! You might want to include some sort of indicator of where the "safe room" is with a different style / color of door -- like Metroid does with colors to show which bombs you need to use to get inside. I was getting frustrated with the lack of healing opportunities because I started exploration from the bottom and made my way up systematically, so it was one of the last rooms I found. I just don't want people to quit your game prematurely because it deserves to be played through to the end.
I like that puzzles [like the box pushing] stay solved, even if you leave the area and [most of] the enemies stay dead [randomly, the mushroom in the room with the long table on the left side of the map and the bat in the wine cellar looking room both came back, but none of the others?].
I think the credit roll being silent is very fitting for that ending. And the post credits scene was cute. Overall a really fun 30ish minute adventure!