The end of the world: Start with a gun and build a tank in ten days

Wake up to a global catastrophe.
Awaken the god-level munitions system at the beginning, and you can get munitions by killing zombies.
"Kill a first-level zombie and get a Barrett sniper rifle with unlimited bullets!"
"Kill the zombie king and get the strongest T-14 RV fortress with unlimited durability!"
"Kill the mutant ancient tree and get a zombie girl with unlimited loyalty!"
"Ding, congratulations, you successfully stopped the zombie tide and got a box of Du Mous!"
Lin Nan: Damn, I'm so naive, you tell me what this is for?
System: Fill with water!