#monoplague

There are 3 major sections of the City: Upper City, Main City, and Lower City.

Upper City is the rooftops area; various vertical sections combined with an upper area that lets you fall to lower areas. 

Main City is where you start, and is more ground level, more horizontal then vertical. 

Lower City is essentially a network of tunnels below the city. It'll be less spacious then the other two areas.

Each section has a "switch" you need to activate. Switch is a broad term but it'll basically open up the rest of THAT area. The main example is that for the Main City you need to turn on the power for the moving platforms and gates to work. 

Going into further detail about the specifics of the areas, each one also follows a sort of theme.

Upper City has ash blowing around; it'll give a sense of desolation and sort of emptiness.

Main City is overrun with plantlife; there are also pools of water here and there but mostly there's going to be a ton of plants.

Lower City is man-made tunnels that have been flooded, water is much more prevalent here then it is in the Main City.

Enemy designs are various hostile wildlife and probably machinery [Machinery might come to life after the power is turned on. Will work on this.]