wagtail/client/scss/components/forms/_radio-checkbox.scss

@use 'sass:math';

$size: 30;
$marker-size: 18;
$marker-offset: math.div($size - $marker-size, 2) - 1;
$radio-checkbox-label-gap: theme('spacing.[2.5]');
$radio-checkbox-line-gap: theme('spacing.[2.5]');

// Both input types are very similar in appearance and layout.
@mixin radio-checkbox-base() {
  @include input-base();
  display: inline-block;
  position: relative;
  height: rem($size);
  width: rem($size);
  cursor: pointer;
  margin-inline-end: $radio-checkbox-label-gap;

  &::before {
    content: '';
    position: absolute;
    top: rem($marker-offset);
    inset-inline-start: rem($marker-offset);
    width: rem($marker-size);
    height: rem($marker-size);
  }

  &:checked::before {
    background: $color-teal;

    @media (forced-colors: active) {
      background: Highlight;
    }
  }
}

input[type='radio'] {
  @include radio-checkbox-base();
  display: inline-block;
  border-radius: theme('borderRadius.full');

  &:checked::before {
    mask-image: url('#{$images-root}icons/radio-full.svg');
  }
}

input[type='checkbox'] {
  @include radio-checkbox-base();
  border-radius: theme('borderRadius.sm');
  // Legacy alignment for checkboxes, particularly within listings.
  vertical-align: bottom;

  &::before {
    // Checkboxes look better with a slightly larger offset.
    top: rem($marker-offset + 1);
    inset-inline-start: rem($marker-offset + 1);
  }

  &:checked::before {
    mask-image: url('#{$images-root}icons/tick.svg');
  }
}