There are small details like laying out roads and making power lines go over them etc that are super-fiddly too.

I know this because I played around with my own simcity for a while, first in true 3D (making curvy roads look nice is damn difficult) and then a 2D grid.

Here's a screenshot I was particularly proud of - the effort to get to that point was more than it looks! http://media.tumblr.com/c9b51ca1eb2b3e89eb8d5af0f560ec34/tum...

More on my algos http://williamedwardscoder.tumblr.com/post/49797579721/willc...

I was going to procedurally produce the buildings using a variation on Eisenscript https://sites.google.com/site/williamedwardscoder/home/exten... with variables in the script based on things like price, distance to other zones, scores etc

I look at the files you link and think "yeah!". I put my city simulation into a Web Worker and the UI in the browser thread though.