There seems to be a mistake on the last core upgrade, because the number displayed for ''core mana production'' are lower in the last upgrade than in the previous one. I also wonder if there is one zero too many on the ''next level up'' display, due to the fact that it seems to be implied in the next paragraph that he could have upgraded again, even though he clearly can't, if that number is correct.
Dear author can you make a map of the dungeon? And don't make the female character unrealistically stupid. Lastly, you should try improve more on describing the layout of the dungeon.
Amewisoemae