twocol_section.css in Drupal 10

/*
 * @file
 * Provides the layout styles for two-column layout section.
 */

.layout--twocol-section {
  display: flex;
  flex-wrap: wrap;
}

.layout--twocol-section > .layout__region {
  flex: 0 1 100%;
}
/* Medium */
@media screen and (min-width: 48em) { /* 768px */
  .layout--twocol-section {
    margin-right: -1.5%;
    margin-left: -1.5%;
  }
  .layout--twocol-section > .layout__region {
    margin-right: 1.5%;
    margin-left: 1.5%;
  }

  .layout--twocol-section.layout--twocol-section--50-50 > .layout__region {
    flex: 0 1 47%;
  }

  .layout--twocol-section.layout--twocol-section--33-67 > .layout__region--first,
  .layout--twocol-section.layout--twocol-section--67-33 > .layout__region--second {
    flex: 0 1 30%;
  }

  .layout--twocol-section.layout--twocol-section--33-67 > .layout__region--second,
  .layout--twocol-section.layout--twocol-section--67-33 > .layout__region--first {
    flex: 0 1 64%;
  }

  .layout--twocol-section.layout--twocol-section--25-75 > .layout__region--first,
  .layout--twocol-section.layout--twocol-section--75-25 > .layout__region--second {
    flex: 0 1 22%;
  }

  .layout--twocol-section.layout--twocol-section--25-75 > .layout__region--second,
  .layout--twocol-section.layout--twocol-section--75-25 > .layout__region--first {
    flex: 0 1 72%;
  }
}