Really interesting concept! The ability to hot swap items is incredibly interesting as it leads to really good risk reward factors, and that feeling of dread when you realise you just took out half your inventory for an item that you couldn't place in time for the boss. I feel like where it could be improved would be the presentation of killing other enemies outside of the bosses, as it took me a long time to realise that I was losing health from it all, your stats whilst using the inventory could also be a bit more obvious as when you're focusing on adding items you don't really notice it, and if it was more obvious I feel that players would try to be more strategic rather then filling all the space :)