main content a box, main content a supplemtal text b sidebar, supplemtal text b main content a sidebar {
  border: solid; }

supplemtal text b sidebar {
  background: gray; }

/********/
mammal, human {
  blood: warm; }

mammal.furry.quadruped, human.furry.quadruped, dog.furry {
  fur: lots;
  legs: 4; }

human {
  says: "hello"; }

dog {
  says: "woof"; }

/********/
region.country inhabitant.mouse, region.country citizen.mouse, region.country tax-payer.mouse {
  eats: cheddar; }

region.city inhabitant.mouse, region.city region.country citizen.mouse, region.country region.city citizen.mouse, region.city tax-payer.mouse {
  eats: camembert; }

region.country citizen {
  ssn: 123 45 6789; }

region tax-payer {
  rate: 17%; }

/********/
foo, .a.bar, hux {
  color: red; }

.a.bar {
  background: gray; }

/********/
foo, .a.bar, hux {
  color: red; }

hux, .bar.a {
  background: blue; }