node.city { color: #801010; }

[ Bremen ] { class: city; }
[ Cuxhaven ] { class: city; }
[ Flensburg ] { class: city; }
[ Hamburg ] { class: city; }

( German Cities
  [ Bremen ]
  [ Cuxhaven ]
  [ Flensburg ]
  [ Hamburg ]
) { nodeclass: city; }

[ Cuxhaven ] --> [ Bremen ]
