discourse/app/assets/stylesheets/common/components/d-toggle-switch.scss

.d-toggle-switch {
  --toggle-switch-width: 45px;
  --toggle-switch-height: 24px;

  &:focus {
    .d-toggle-switch__checkbox-slider {
      outline: 2px solid var(--tertiary);
    }
  }

  &:hover {
    .d-toggle-switch__checkbox-slider {
      background-color: var(--primary-high);
    }

    .d-toggle-switch__checkbox[aria-checked="true"]:not([disabled])
      + .d-toggle-switch__checkbox-slider {
      background-color: var(--tertiary-hover);
    }
  }

  display: flex;
  align-items: center;

  &__label {
    position: relative;
    display: inline-block;
    cursor: pointer;
  }

  &__checkbox {
    position: absolute;
    visibility: hidden;
  }

  &__checkbox[aria-checked="true"] + .d-toggle-switch__checkbox-slider {
    background-color: var(--tertiary);
  }

  &__checkbox[aria-checked="true"] + .d-toggle-switch__checkbox-slider::before {
    left: calc(var(--toggle-switch-width) - 22px);
  }

  &__checkbox[disabled] + .d-toggle-switch__checkbox-slider {
    opacity: 0.5;
    cursor: not-allowed;

    &::before {
      cursor: not-allowed;
    }
  }

  &__checkbox-slider {
    display: inline-block;
    cursor: pointer;
    background: var(--primary-low-mid);
    border-radius: 16px;
    width: var(--toggle-switch-width);
    height: var(--toggle-switch-height);
    margin-right: 0.5em;
    position: relative;
    vertical-align: middle;
    transition: background 0.25s;

    .d-icon {
      font-size: var(--font-down-1);
      color: var(--secondary);
      left: 7px;
      top: 7px;
      position: absolute;
    }
  }

  &__checkbox-slider::before,
  &__checkbox-slider::after {
    content: "";
    display: block;
    position: absolute;
    cursor: pointer;
  }

  &__checkbox-slider::before {
    background: var(--secondary);
    border-radius: 50%;
    width: calc(var(--toggle-switch-width) / 2.5);
    height: calc(var(--toggle-switch-width) / 2.5);
    top: 3.5px;
    left: 4px;
    transition: left 0.25s;
  }
}