gab-social/app/javascript/gabsocial/components/media_gallery/index.scss

.media-item {
  display: block;
  float: left;
  border: none;
  box-sizing: border-box;
  position: relative;
  border-radius: 4px;
  overflow: hidden;

  &.standalone {
    media-item-gifv-thumbnail {
      transform: none;
      top: 0;
    }
  }

  &__thumbnail {
    display: block;
    cursor: zoom-in;
    text-decoration: none;
    color: $secondary-text-color;
    line-height: 0;
    position: relative;
    z-index: 1;

    &,
    img {
      @include size(100%);
    }

    img {
      object-fit: cover;
    }
  }

  &__gifv {
    cursor: zoom-in;
    object-fit: cover;
    position: relative;
    top: 50%;
    transform: translateY(-50%);
    z-index: 1;

    @include size(100%);
  }
}

.media-gallery {
  box-sizing: border-box;
  margin-top: 8px;
  overflow: hidden;
  border-radius: 4px;
  position: relative;
  width: 100%;

  &__preview {
    object-fit: cover;
    z-index: 0;
    background: $base-overlay-background;

    @include size(100%);
    @include abs-position(0, auto, auto, 0);

    &--hidden {
      display: none;
    }
  }

  &__gifv {
    overflow: hidden;
    position: relative;

    @include size(100%);

    &.autoplay {
      .media-gallery__gifv__label {
        display: none;
      }
    }

    &:hover {
      .media-gallery__gifv__label {
        opacity: 1;
      }
    }

    &__label {
      display: block;
      color: $primary-text-color;
      background: rgba($base-overlay-background, 0.5);
      padding: 2px 6px;
      border-radius: 2px;
      z-index: 1;
      pointer-events: none;
      opacity: 0.9;
      transition: opacity 0.1s ease;

      @include text-sizing(11px, 600, 18px);
      @include abs-position(auto, auto, 6px, 6px);
    }
  }
}

.spoiler-button {
  z-index: 100;

  @include size(100%);
  @include abs-position(0, auto, auto, 0);

  &--minified {
    display: block;

    @include size(auto);
    @include abs-position(4px, auto, auto, 4px, false);
  }

  &--hidden {
    display: none;
  }

  &__overlay {
    display: block;
    background: transparent;
    border: 0;

    @include size(100%);

    &__label {
      display: inline-block;
      background: rgba($base-overlay-background, 0.5);
      border-radius: 8px;
      padding: 8px 12px;
      color: $primary-text-color;

      @include text-sizing(14px, 500);
    }

    &:hover,
    &:focus,
    &:active {
      .spoiler-button__overlay__label {
        background: rgba($base-overlay-background, 0.8);
      }
    }
  }
}