Items are almost completely implemented in my game right now. Again, a lot of interesting logic to think about. When you get an item, it has to disappear, right? But when does it reappear? Over time? When you return to that particular map? When you return to that particular map? When you return to that particular map after having been to a certain number of rooms? Never?
The next step is items dropped from enemies. This will surely require some balancing as the drop rate and what they drop will have to all be considered. I do not think there will be a currency in the game, though, so it might just be health that I need to consider.