War Chess: Can I Upgrade Resources?

Xu Wei opened his eyes. A barrage came into view. Want to become a god? Go and clear the level if you want! As long as you clear the world of war chess, you will become a real god! Xu Wei entered the world of war chess nervously and opened a treasure box. You got: 1 unit of purified water. You got: 20 units of iron. You got: 20 units of Brass. You get: a treasure map. Please select a resource to upgrade. The moment the last line appeared, Xu Wei knew that he was the god of the chess world.