Great idea and lovely implementation. If I could make one nitpick, it would be to add some tags so that it shows up as a Twitter card for when people tweet about it:

https://dev.twitter.com/cards/overview

https://cards-dev.twitter.com/validator

(FWIW, looks fine on the Facebook linter because of the og:meta tags https://developers.facebook.com/tools/debug/sharing/?q=http%...)