_dropdown.scss

details.sd-dropdown {
  position: relative;

  .sd-summary-title {
    font-weight: 700;
    // don't overlap the chevron
    padding-right: 3em !important;
    user-select: none;
    display: inline-flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;

    .sd-summary-text {
      flex-grow: 1;
      line-height: 1.5;
      padding-right: 0.5rem;
    }

    .sd-summary-state-marker {
      position: absolute;
      right: 1em;
      top: 50%;
      transform: translateY(-50%);
      pointer-events: none;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 0.75em;
    }

    // The hover effect should only change opacity, not transform.
    // We are transforming the chevron elements instead, see below.
    &:hover .sd-summary-state-marker svg {
      opacity: 1;
    }
  }

  &:hover {
    cursor: pointer;
  }

  .sd-summary-content {
    cursor: default;
  }

  summary {
    // hide the default triangle marker
    list-style: none;
    padding: 1em;

    // Ellipsis added when no title
    .sd-octicon.no-title {
      vertical-align: middle;
    }
  }

  &[open] summary .sd-octicon.no-title {
    visibility: hidden;
  }

  // chrome doesn't yet support list-style
  summary::-webkit-details-marker {
    display: none;
  }

  summary:focus {
    outline: none;
  }

  .sd-summary-icon {
    margin-right: 0.5em;
  }

  .sd-summary-icon svg {
    opacity: 0.8;
  }

  summary:hover .sd-summary-up svg,
  summary:hover .sd-summary-down svg {
    opacity: 1;
  }

  .sd-summary-up svg,
  .sd-summary-down svg {
    display: block;
    opacity: 0.6;
  }

  .sd-summary-up,
  .sd-summary-down {
    pointer-events: none;
    position: absolute;
    right: 1em;
    top: 1em;
  }

  &[open] > .sd-summary-title .sd-summary-down {
    visibility: hidden;
  }

  &:not([open]) > .sd-summary-title .sd-summary-up {
    visibility: hidden;
  }

  // Chevron transitions
  .sd-summary-chevron-right i,
  .sd-summary-chevron-down i {
    display: inline-block;
    transform-origin: center;
    opacity: 0.6;
  }

  // The chevron rotation animations are applied to
  // the icon inside the dropdown title div
  &[open] > .sd-summary-title .sd-summary-chevron-right i {
    transform: rotate(90deg);
    animation: rotate-to-90 0.25s ease-in-out;
  }

  &[open] > .sd-summary-title .sd-summary-chevron-down i {
    transform: rotate(-180deg);
    animation: rotate-to-negative-180 0.25s ease-in-out;
  }

  &:not([open]) > .sd-summary-title .sd-summary-chevron-right i {
    transform: rotate(0deg);
    animation: rotate-to-0-from-90 0.25s ease-in-out;
  }

  &:not([open]) > .sd-summary-title .sd-summary-chevron-down i {
    transform: rotate(0deg);
    animation: rotate-to-0-from-negative-180 0.25s ease-in-out;
  }

  > .sd-summary-title:hover .sd-summary-chevron-right i,
  > .sd-summary-title:hover .sd-summary-chevron-down i {
    opacity: 1;
  }

  // Combined transforms for each state with hover. These cover
  // the cases where the chevron is rotated, say, when the dropdown
  // is open or if the chevron starts rotated (e.g. in the down-up
  // state).
  &:not([open]) > .sd-summary-title:hover .sd-summary-chevron-right i {
    transform: scale(1.1);
  }

  &:not([open]) > .sd-summary-title:hover .sd-summary-chevron-down i {
    transform: scale(1.1);
  }

  &[open] > .sd-summary-title:hover .sd-summary-chevron-right i {
    transform: rotate(90deg) scale(1.1);
  }

  &[open] > .sd-summary-title:hover .sd-summary-chevron-down i {
    transform: rotate(-180deg) scale(1.1);
  }

  // Hide the card body border when not open
  &:not([open]).sd-card {
    border: none;
  }
  &:not([open]) > .sd-card-header {
    border: 1px solid var(--sd-color-card-border);
    border-radius: 0.25rem;
  }

  // Transition animation
  &.sd-fade-in[open] summary ~ * {
    animation: sd-fade-in 0.5s ease-in-out;
  }

  &.sd-fade-in-slide-down[open] summary ~ * {
    animation:
      sd-fade-in 0.5s ease-in-out,
      sd-slide-down 0.5s ease-in-out;
  }
}

.sd-col > .sd-dropdown {
  width: 100%;
}

.sd-summary-content > .sd-tab-set:first-child {
  margin-top: 0;
}

@keyframes sd-fade-in {
  0% {
    opacity: 0;
  }

  100% {
    opacity: 1;
  }
}

@keyframes sd-slide-down {
  0% {
    transform: translate(0, -10px);
  }

  100% {
    transform: translate(0, 0);
  }
}

@keyframes rotate-to-90 {
  from {
    transform: rotate(0deg) scale(1.1);
  }
  to {
    transform: rotate(90deg) scale(1.1);
  }
}

@keyframes rotate-to-0-from-90 {
  from {
    transform: rotate(90deg) scale(1.1);
  }
  to {
    transform: rotate(0deg) scale(1.1);
  }
}

// TODO: These keyframes are disabled for now to maintain
// parity with Sphinx Design upstream, which does not implement
// the down-up chevron animation.

// @keyframes rotate-to-negative-180 {
//   from {
//     transform: rotate(0deg) scale(1.1);
//   }
//   to {
//     transform: rotate(-180deg) scale(1.1);
//   }
// }

// @keyframes rotate-to-0-from-negative-180 {
//   from {
//     transform: rotate(-180deg) scale(1.1);
//   }
//   to {
//     transform: rotate(0deg) scale(1.1);
//   }
// }