0%;
          width: 100%;
          position: relative;
          overflow: hidden;
        }
        .table-of-contents li a {
          color: #fff;
        }
        .box {
          width: 50%;
          height: 50%;
          transform: translateX(-100%);
          background-color: #444;
          transition: transform .3s;
        }
        #green .box, #red .box {
          position: absolute;
          right: 0;
          transform: translateX(100%);
        }

        .scrolled .box,
        #gre