Nice game! Do the "defences" even do anything? It does not look so...
I'm not sure, either. Yet, somehow, I still want as many as possible.
The enemy will always be able to do 1 damage to you. However if the enemy has 40 attack and you have 20 defense, they will do 20 damage to you, and if you have 45 defense, they will still do 1 damage to you