A free, open source C# framework for making games, or your own game engine. Direct access to native APIs and Vulkan, with the low-level libraries around them. The foundation under Kitten Space Agency and RimWorld's Waylith engine.
A great starting point for your 2D controller. Making use of all the hidden tricks like coyote, buffered actions, speedy apex, anti grav apex, etc
Authoring Tools Framework (ATF) is a set of C#/.NET components for making tools on Windows. ATF has been in continuous development in Sony Computer Entertainment's (SCE) Worldwide Studios central tools group since early 2005. ATF has been used by most SCE first party studios to make many custom tools such as Naughty Dog’s level editor and shader editor for The Last of Us, Guerrilla Games’ sequence editor for Killzone games (including the Killzone: Shadow Fall PS4 launch title), an animation blending tool at Santa Monica Studio, a level editor at Bend Studio, a visual state machine editor for Quantic Dream, sound editing tools, and many others.