For an online demo, go to: https://threemagpiesarguingsemantics.github.io/SimplePhysicsEngine/source/
I wrote this simple 2D convex rigid body physics engine because the algorithms were fascinating. It's been implemented entirely in pure JavaScript+ HTML+ CSS over two summers.
The maths are based on a series of wonderful articles by Chris Hecker from 1996, along with the calculation of rotational inertia of polygons taken from the point-mass inertia equation in a physics book I had. http://www.chrishecker.com/Rigid_body_dynamics
When writing this project, I had not studied linear algebra; much credit goes to the 3b1b, an excellent YouTube series, for teaching me what I needed. https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw