Ammunition requires gunpowder

[British_Petroleum]

Gunpowder would be a new thing to the manufactured. Perhaps the earlier ammunition would not require gunpowder so the player can still defend himself early game.

Ammunition should also be more efficient than laser towers, in terms of energy used to manufacture them and damage dealt. Also a balance issue. Imo, laser towers should be very power hungry, but do more damage eventually with more research. The high energy useage with also be repaid by the convenience of not needing to refill them with ammunition