While I love the city/base building game genre I always hated the simulation aspects of it. Those games end up with you waiting for resources to accumulate and the game becomes either too easy or too hard after a while.
I am trying to make a game that is deterministic. You can build as much as you want with the effects on your city immediately visible. If your city exports more resources than it imports, you get points that you can use to unlock new buildings. Issues (for example: traffic jams) will cost you points.
Almost everything in this games is procedurally generated, which has benefits for LOD handling, creating building variety and gameplay.
The game is written in C with the help of some header only libraries. The procedural generation code is written in a custom lisp-like language.