An example Unity project for ShapeMath2D with demos. ShapeMath2D is available as a gist here.
The goal of ShapeMath2D is to provide a common set of efficient tools to solve geometry problems in 2D. ShapeMath2D is a single-file library that contains static functions for intersections between circles, AABBs, and convex polygons:
...as well as algorithms for computing the minimum bounding circle (magenta) and convex hull (red) of a set of points:
ShapeMath2D can certainly be improved with even more efficient algorithms! Currently, it is very good at what it sets out to do and is an excellent C# reference.