I'm making a Capitalism II clone with Mini Metro graphics.
The server is written in C++ (Boost and stuff), the client in JavaScript (Electron & PixiJS). CLion for the former, WebStorm for the latter, basically I'm a JetBrains fan :) and everything is in Mercurial.
All "art" currently consists of lines and shapes, although I'd like to use proper icons for goods types, but not sure where to get them (pre-drawn sets, if they exist, probably won't cover everything I need).
This is a prototype for a commercial game, so it won't be FOSS (unless I give up on the idea).