The building mechanic is not unheardof, but it's nice to see a roguelike with it. I found that it feels like the +3 damage thing is kinda overpowered, effectively quadrupling the damage, and I didn't even want to take on any more items... but killing enemies faster turned out to be more fun honestly.
I'm wondering how are the maps built? They seem rather chaotic and there are new ones each run, did you use procedural generation?