小编Jor*_*era的帖子

html,
body {
  height: 100%;
}

.parent {
  /* Parent's height and width are unknown,
     it could be dynamic, e.g. parent is part of a flex layout. */
  height: 80%;
  width: 90%;
  border-style: solid;
  border-width: 2px;
  border-color: black;
}

.child {
  width: 90vw;
  /* 90% of viewport vidth */
  height: 50.625vw;
  /* ratio = 9/16 * 90 = 50.625 */
  max-height: 90vh;
  max-width: 160vh;
  /* 16/9 * 90 = 160 */
  margin: auto; …