One framework for creating powerful cross-platform games
Accuracy-focused XNA4 reimplementation for open platforms
Stride (formerly Xenko), a free and open-source cross-platform C# game
A game framework written with osu! in mind.
Svelto ECS C# Entity Component System
Download Cryptic Roblox executor for keyless scripting. Free for PC.
API (C#) for simulating certain aspects of a ZX spectrum for porting.
3D .NET engine for Windows, Linux, Mac
Open Source Virtual World and MMOG Development Platform