#my-box {
  overflow:hidden; }

#my-box div, #my-box span {
  display:block; float:left; margin:5px;
  width:20px; height:20px;
  background:#CCC; }

#my-box span {
  background:orange; }

/* step one */
#my-box.step-one div:nth-of-type(2n+2) {
  background:blue; }

/* step two */
#my-box.step-two div~div {
  background:blue; }
 
/* step three */
#my-box.step-three div~div, #my-box.step-three div~div~div~div, #my-box.step-three div~div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div~div~div~div~div~div {
  background:blue; }
 
#my-box.step-three div, #my-box.step-three div~div~div, #my-box.step-three div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div~div~div~div~div, #my-box.step-three div~div~div~div~div~div~div~div~div~div~div~div~div {
  background:#CCC; }