/* Mobile : sidebar après le post */
#main {
  display: flex;
  flex-direction: column;
}
.sidebar       { order: 3; }
.page          { order: 1; }
.page__related { order: 2; }

/* Desktop : layout float du thème */
@media (min-width: 64em) {
  #main    { display: block; }
  .sidebar       { order: unset; }
  .page          { order: unset; }
  .page__related { order: unset; }
}