background .slide-background {
      opacity: 0.7 !important;
      /*background: none !important;*/ /* for printing ! */
    }

    .print-pdf .reveal .slide-background {
      opacity: 0.7 !important;
    }

    .dim-background .slide-background.past {
      display: none !important;
    }

    .dim-background .slide-background.future {
      display: none !important;
    }

    .chapter-background .slide-background.past {
      display: none !important;
    }

    .chapter-background .slide-background.fu