Great concept! The inventory mechanic worked really well, in my opinion. At first, I was kind of annoyed with the number of items I had to cycle through constantly, but after a while it became more of a search for the "perfect system" (for me, that was a key if I had it, sword, torch, then treasure). I was considering leaving the treasure behind at first, since it wasn't serving any purpose for me, but then I realized that you can use it to create a shield to fight the monsters, which was a really interesting mechanic (whether or not it was intentional)! Just a couple things I noticed:
1. The combat system was a bit difficult to master. Since the player is so slow, and you can only attack in one direction at a time, fighting multiple green monsters can really take your health down. Using treasure as a shield helps, but maybe there's a way to improve the combat.
2. When you're emptying the inventory, you can accidentally empty it all against a wall so that you can only target the outer items. Not a huge problem, since you can just pick them up and throw some of them elsewhere to get to the inner items, but maybe increasing the hitboxes of dropped items might make it a little easier to manage.
Overall, it's a great game, and it would be really cool to expand the concept over more levels, enemies, and items!