I really liked the "Get the lowest score you can" focus in the game, makes you really think about the map and how to traverse it and what items to get and not to get, although I'd have liked that idea being more enforced in gameplay moments, off the top of my head I could only think of giving a maximum score you could get in any given level or something like that. I feel that the concept of "only one", even though you could have implemented it into the game (maybe by only carrying one item at any time) , was interpreted with a certain originality and pureness that the game breathes, supported by the music and art style.
Another thing I thought of while playing the game was that it would be more engaging if the player had a certain obstacle or enemy that made them think faster about their actions. As it is right now, you could wait whatever you want to take your next action, and that could possibly suck the fun out of the game.
I feel like, with a harder focus on getting a low score and a good level design (which I won't comment on because it's not something that I know enough, but in my lack of knowledge, I found it good enough in your build), it could actually be an interesting game.