&__gallery {

  .main {

    &__img {
      opacity: 0;
    }
  }

  input[type="radio"] {
    display: none;
  }

  // galleryAnimation 定義
  @mixin galleryAnimation($name, $items) {

    @for $i from 1 through $items {

      .#{$name}#{$i}:checked {

        & ~ .intro__gallery {

          .main {

            &__img {

              &--#{$i} {
                opacity: 1;
              }
            }
          }

          .thumbnail {

            li:nth-child(#{$i}) {

              .image {
                opacity: 0.8;
              }
            }
          }
        }
      }
    }
  }
}