Personally I'd like to have a lille border to separate the different boxes. If you guys don't like it, just let me know and I'll close the PR again. :-)
@SaaldjorMike isnt border:1px better?
@f0o: Seems like using border:1px gives the following: https://i.imgur.com/gX4TkIJ.png
@SaaldjorMike is the default then 'em' or what unit? I dislike having the border parameter without a unit. Could lead to different outcomes depending on the browser's assumptions of units..
Added borders between elements on availability map.