In the End of the World, My Items Can Be Upgraded Quickly

A fruit knife and a wooden stick constitute = a spear; You can upgrade it by using it. Inferior spear-refined spear-...-Shoulder-mounted rocket launcher, what is it? A few wooden roots, some canvas, the combination = a tent; Accommodation can be upgraded, inferior tent - portable tent - + three-wheeled - RV what the hell? The disaster is coming, others are escaping, and I am... What? Who's knocking on the door outside my base? The eldest lady of the city lord? Which city? Let her queue up!