It'll be good if the stackable items(maybe also the hearts and shields) only display once, and the quantity just shows as an index. I assume it won't be that easy because you also need to handle the transfer of items.
The logic of the Discount Voucher is not right, I suppose it was designed to max at 50%, so maybe just changing the logic from 0.9^5 to 0.9*5 can fix it. (The ability of the Gambler is way too OP with this glitch.)
The validation of the maximum of some items is not restrictive; like you can just break the upper bound by using Echo Orb/Egg.
But anyway, it's a great game, enjoyed it ;)
