text: /*jslint sloppy:true,white:true*/
  var canvas = document.querySelector('canvas');
  var ctx = canvas.getContext('2d');
  
  ctx.fillStyle = 'black';
  ctx.fillRect(0, 0, 500, 500);
  
  ctx.strokeStyle = 'white';
  function line(x1, y1, x2, y2) {
      ctx.beginPath();
      ctx.moveTo(x1, y1);
      ctx.lineTo(x2, y2);
      ctx.stroke();
  }
  function drawFrame() {
      ctx.fillStyle = 'rgba(0,0,0,0.2)';
      ctx.fillRect(0, 0, 500, 500);
      var i;
      for (i = 0; i <= 500; i = i + 10) {
          ctx.strokeStyle =
              'rgb(' + (i*255/500) + ',0,255)';
          line(Math.random() * 500, i, 500, 500);
      }
  }
  setInterval(drawFrame, 200);