.rpanel.grayscale {
  @header-color: rgba(0, 0, 0, 0.75);
  @header-bg-color: rgba(255, 255, 255, 0.15);
  @content-bg-color: rgba(0, 0, 0, 0.2);

  @border-color: rgba(0, 0, 0, 0.5);

  > header {
    border-color: @border-color;
    background-color: @header-bg-color;
    color: @header-color;

    .rpanel-icon {
      color: (#fff - @header-color);
      text-shadow: 2px 2px 2px @header-color;
    }

    .rpanel-title {
      text-shadow: 1px 1px 1px mix((#fff - @header-color), (#fff - (#fff - @header-color)), 65%);
    }

    .rpanel-control {
      border-color: @content-bg-color;

      & * {
        color: @header-color;
        text-shadow: 1px 1px 1px (#fff - @header-color);
      }

      &.active {
        background-color: @content-bg-color;
      }

      &:hover {
        background-color: fadeout(@content-bg-color, 10%);
      }
    }

    .rpanel-tabs {

      .rpanel-tab {

        .rpanel-icon, .rpanel-title {
          color: mix(@header-bg-color, @header-color, 50%);
          text-shadow: none;
        }

        &.active {
          border-color: fadein(@header-bg-color, 50%);
          background-color: @content-bg-color;

          .rpanel-icon, .rpanel-title {
            color: mix(@header-bg-color, @header-color, 25%);
          }
        }

        &:not(.active):hover {
          background-color: fadeout(@content-bg-color, 10%);
        }
      }
    }
  }

  > .rpanel-body {
    background-color: @header-bg-color;
    border-color: @border-color;

    .rpanel-toolbar {
      background-color: @content-bg-color;
      border-bottom: 0 none;
    }
    .rpanel-content {
      background-color: transparent;
      box-shadow: 0 2px 0 @content-bg-color inset;
    }
  }

  &.rpanel-state-fullscreen > .rpanel-body > .rpanel-tab-body.active > .rpanel-content {
    background-color: darken(fadein(@header-bg-color, 70%), 5%);
  }
}