blockscout/apps/block_scout_web/assets/css/components/_dropdown.scss

// These styles extend the default Bootstrap styles
.dropdown-menu {
  border-radius: 8px !important;
  border: none;
  box-shadow: $box-shadow;
  padding: 0;
  width: 100%;

  &.right {
    left: auto;
    right: 0;
  }

  .nav-item & {
    border-top-left-radius: 0 !important;
    border-top-right-radius: 0 !important;
    top: 45px;

    .dropdown-item:first-child {
      border-top-left-radius: 0;
      border-top-right-radius: 0;
    }
  }
}

.dropdown-item {
  font-size: 12px;
  padding: 10px 20px;

  &:hover {
    color: #fff;
  }

  &:first-child {
    border-top-left-radius: 8px;
    border-top-right-radius: 8px;
  }

  &:last-child {
    border-bottom-left-radius: 8px;
    border-bottom-right-radius: 8px;
  }

  &.header {
    &,
    &:hover,
    &:active {
      padding-left: 10px;
      background-color: transparent;
      cursor: default;
      color: #333;
      font-weight: 700;
    }
  }
  
  &.active {
    background-color: $secondary;
  }

  &.division {
    border-top: 1px solid $base-border-color;
  }
}

.dropdown-search-icon {
  color: $gray-300;
  left: 8px;
  pointer-events: none;
  top: 5px;
}

.dropdown-search-field {
  padding-left: 2rem;
}

.dropdown-toggle::after {
  margin-left: 0.71em;
}