A game framework written with osu! in mind.
Game engine supporting many 3D/2D formats and graphic effects
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
3D .NET engine for Windows, Linux, Mac
Gives agents personality, moods, emotions and emotional attachments.
Hungry Hero is an open source Flash game built on Starling Framework.
Cross-platform 2D game engine