* adopt euclid as foundational points/geometry library
* collision detection
* add bounding boxes to `Shape` trait
* scene maintains AABB tree of shapes in the scene
* use AABB tree to quickly find candidates for closer inspection
* good overview:
https://www.azurefromthetrenches.com/introductory-guide-to-aabb-tree-collision-detection/
* use separating axis theorem to determine if it is actually a collision
* have to do O(m*n) checks on each primitive shape
* clipping
* Vatti is most general
* Greiner-Hormann is faster, but convex only
