I quite often take a look at the code of Spectrum: https://github.com/withspectrum/spectrum.

It's my go-to (with https://github.com/Automattic/wp-calypso) to get an idea of how they solved a particular issue in their React app.

I'm really thankful to them for open sourcing their product. I wish more companies would go this way.

Anyway, congratz to Max (also author of Styled Components) and the rest of the team!