Using css modules compose inside media queries.

component.css

.container {
  compose: row from './flex.css';
}

@media (min-width: 768px) {
  .container {
    compose: column from './flex.css'
  }
}

flex.css

.row {
  display: flex;
  flex-direction: row;
}

.column {
  display: flex;
  flex-direction: column;
}