@media screen and (max-width: 768px) {
  main {
    /* background-color: red; */
    flex-direction: column;
    align-items: center; /*but not needed because no space left over*/
  }

  #homework,
  #milestones,
  #terms {
    /*width rules needed to undo desktop version */
    width: 100%;
    max-width: 100%;
  }
}