I like the concept of being able to buy anything in the game, it reminds me of how Baba is You turns the expectation of game rules on its head. I would like to see this expanded out to a few more rooms, because it doesn't get enough time to shine as a short demo.
It was not clear for some time that using different items while attacking was doing anything other than a standard attack, so some indication of that would be good (maybe swinging the item itself or a sound effect.).