Thanks all for the love and suggestions! I made this site more than five years ago and am so happy it helps folks daily. This is a project that can always be expanded and what's there is never enough. Super helpful to hear from y'all on some low-hanging next steps. Happy to hear more suggestions on what next steps and/or can't-be-left-out topics. (With the eye towards beginners and folks without a ton of math background – the goal isn't to be a drop-in for Box2D or Unity or whatever but to outline the fundamentals and get folks started.)