A Chess API (and, later, web site) for playing with friends via web and email. Almost certainly wheel-reinventing, but this is for personal learning, and I've also not come across many Chess960 'digital correspondence chess' services.
make,make allormake docswill build everything (presently only the docs).make open-docswill open the docs in your default browser after building.
The name is a pun on REST and Half-Life's 'Opposing Force' expansion pack.