[timmy-turner]

Never having used C# myself but I sometimes play https://github.com/OpenRA/OpenRA (an open source Command & Conquer clone) which is written in C#, runs on all major OSes and uses Mono at least on Linux.

[ahmedalsudani]

Wow that is crazy. C&C was a childhood favourite, and I'm so happy to hear it has been cloned as free software!