wagtail/client/scss/components/_dialog.scss

.w-dialog {
  position: fixed;
  display: flex;
  inset-inline-start: 0;
  inset-inline-end: 0;
  bottom: 0;
  top: 0;
  z-index: theme('zIndex.dialog');
  padding: theme('spacing.4');

  &[aria-hidden='true'] {
    display: none;
  }

  &__overlay {
    position: fixed;
    inset-inline-start: 0;
    inset-inline-end: 0;
    bottom: 0;
    top: 0;
    opacity: theme('opacity.40');
    background: theme('colors.black.DEFAULT');
  }

  &__box {
    width: 100%;
    position: relative;
    margin: auto;
    overflow: hidden;
    max-width: theme('maxWidth.2xl');
    z-index: theme('zIndex.dialog');
    background: theme('colors.white.DEFAULT');
    box-shadow: theme('boxShadow.DEFAULT');
    border-radius: theme('borderRadius.md');
    animation: theme('animation.fade-in');

    @include media-breakpoint-up(sm) {
      width: 600px;
    }
    @media (forced-colors: $media-forced-colours) {
      border: 5px solid currentColor;
    }
  }

  &__close-button {
    position: absolute;
    display: inline-flex;
    justify-content: center;
    align-items: center;
    background: transparent;
    padding: 0;
    top: theme('spacing.2');
    inset-inline-end: theme('spacing.2');
    width: theme('spacing.12');
    height: theme('spacing.12');
  }

  &__close-icon {
    width: theme('spacing.4');
    height: theme('spacing.4');
    color: theme('colors.grey.600');
  }

  &__content {
    // Using apply for scrollbars to avoid having to overwrite scrollbar with excess css
    overflow: auto;
    padding: theme('spacing.8');
    max-height: calc(100vh - 180px);
    min-height: min(100vh - 180px, 320px);

    @include media-breakpoint-up(sm) {
      padding: theme('spacing.12');
    }

    @include media-breakpoint-up(md) {
      padding-inline-start: theme('spacing.20');
      padding-inline-end: theme('spacing.20');
    }
  }

  &__icon {
    position: absolute;
    display: none;
    width: theme('spacing.5');
    height: theme('spacing.5');
    color: theme('colors.primary.DEFAULT');
    top: theme('spacing.[0.5]');
    transform: translateY(theme('spacing.2'));
    inset-inline-start: calc(0 - theme('spacing.10'));

    @include media-breakpoint-up(md) {
      display: block;
    }
  }

  &__title {
    position: relative;
    margin-top: 0;
    margin-bottom: theme('spacing.1');
  }

  &__subtitle {
    margin-bottom: theme('spacing.4');
  }

  &__message {
    display: flex;
    align-items: center;
    padding: theme('spacing.5');

    @media (forced-colors: $media-forced-colours) {
      border-bottom: 1px solid currentColor;
    }

    &--info {
      background: theme('colors.info.50');
      color: theme('colors.info.100');
    }

    &--warning {
      background: theme('colors.warning.50');
      color: theme('colors.primary.DEFAULT');
    }

    &--critical {
      background: theme('colors.critical.50');
      color: theme('colors.critical.200');
    }

    &--success {
      background: theme('colors.positive.50');
      color: theme('colors.positive.100');
    }
  }

  &__message-icon {
    width: theme('spacing.5');
    height: theme('spacing.5');
    flex-shrink: 0;
  }

  &__message-header {
    margin-inline-start: theme('spacing[2.5]');
    padding-inline-end: theme('spacing.8');
    color: theme('colors.grey.600');
    font-size: theme('fontSize.14');
  }

  &__message-description {
    margin-bottom: 0;
  }
}