I still dont get how to acquire the coin (or maybe its a golden gemstone, idk) in Dungeon C. Unfortunately, Steam blocked this game in my country, so i cant look up the walkthrough. I assume its inside of the chest, but i have no idea how to open it (maybe it has something to do with the 2 crossed-out symbols in the top-left and top-right of the first room?).
Either way, great game :)