rgba(255, 255, 255, .5) 25%,
        transparent 25%,
        transparent 50%,
        rgba(255, 255, 255, .5) 50%,
        rgba(255, 255, 255, .5) 75%,
        transparent 75%,
        transparent
      );
      background-size: 50px 50px;
      animation: progressanim 2s linear infinite;
    }

    @keyframes progressanim {
      0% {
        background-position: 50px 50px;
      }
      100% {
        background-position: 0 0;
      }
    }
    </style>
  </head>
  <body>
    <canvas id="c" tabindex="1">