.#{$button-root} {
  &--progress {
    .#{$button-root}__wrapper > span:nth-child(2) {
      position: absolute;
      top: var(--button-raise-level);
      left: 0;
      right: 0;
      bottom: calc(var(--button-raise-level) * -1);
      display: flex;
    }
    .#{$button-root}__progress {
      @extend %fill-parent;
      position: relative;
      display: flex;
      flex: 1;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      border-radius: $button-default-border-radius;
      text-indent: 0;
      z-index: 3;
      overflow: hidden;
      transition: border var(--transform-speed) ease-out,
        transform var(--transform-speed) ease-out,
        background var(--transform-speed) ease-out,
        color var(--transform-speed) ease-out;

      > span {
        transition: opacity calc(var(--transform-speed) * 0.5) ease-out
          calc(var(--transform-speed) * 0.75);
      }
      &:before,
      &:after {
        display: flex;
        align-items: center;
        justify-content: center;
        color: rgba(255, 255, 255, 0.65);
        opacity: 0;
        transition: transform var(--transform-speed) ease-out 0.05s,
          opacity calc(var(--transform-speed) * 0.75) ease-out 0.05s;
      }
      &:before {
        content: attr(data-loading);
        display: none;
        transform: translate3d(0, 100%, 0);
      }
      &:after {
        content: attr(data-status);
        display: none;
        transform: translate3d(0, -100%, 0);
      }
    }
    .#{$button-root}__content {
      // safari span inheritance issue
      > span > span,
      > svg {
        transition: opacity 200ms ease-out;
      }
    }
    &.#{$button-root}--active {
      .#{$button-root}__content {
        // safari span inheritance issue
        > span > span,
        > svg {
          opacity: 0.1;
        }
      }
      .#{$button-root}__progress:after,
      .#{$button-root}__progress:before,
      .#{$button-root}__content:after {
        display: block;
      }
    }
    .#{$button-root}__content {
      &:after {
        @extend %fill-parent;
        content: ' ';
        background-color: rgba(0, 0, 0, 0.15);
        transform: translate3d(-100%, 0, 0);
        width: 100%;
        display: none;
      }
    }
  }
  &--start {
    .#{$button-root}__progress {
      &:before {
        opacity: 1;
        transform: translate3d(0, 50%, 0);
      }
    }
    .#{$button-root}__content {
      &:after {
        transition: transform var(--loading-transition-speed) ease-out;
        transform: translate3d(-15%, 0, 0);
      }
    }
  }
  &--errored {
    .#{$button-root}__content {
      &:after {
        background-color: rgba(255, 0, 0, 0.75);
      }
    }
  }
  &--end {
    .#{$button-root}__content {
      &:after {
        transition: transform var(--loading-transition-end-speed)
          var(--loading-transition-timing);
        transform: translate3d(0, 0, 0);
      }
    }
    .#{$button-root}__progress {
      &:after {
        opacity: 1;
        transform: translate3d(0, -50%, 0);
      }
      &:before {
        transform: translate3d(0, 50%, 0);
        opacity: 0;
      }
    }
  }
}