My Final File
<style>
  body {
    background-color:green;
  }
  div {
    text-align:center;
  }
  img {
    height:23vmin;
  }
</style>
<body>
<script>
  var click_ok=true;
  var arr=[6,7,8,9,10,11,12,1,32,33,34,35,36,37,38,27];
  Shuffle(arr);
  var s1="<img src='cards/back.png' n='";
  var s2="' onClick='card_clicked(this);'>";
  var n=0;
  for (var r=0; r<4; r++) {
    document.write('<div>');
    for (var c=0; c<4; c++) {
      document.write(s1 + arr[n] + s2);
      n++;
    }
    document.write('</div>');
  }
  function Shuffle(array) {
    var i,j,temp;
    for (i=array.length-1; i>0; i-=1) {
      j=Math.floor(Math.random()*(i+1));
      temp=array[i]; array[i]=array[j]; array[j]=temp;
    }
  }
  var card1='';
  var back_src='';
  function card_clicked(image) {
    if (back_src=='') {
      back_src=image.src;
    }
    if (image.src==back_src && click_ok) {
      var n=image.getAttribute('n');
      image.src='cards/'+n+'.png';
      if (card1=='') {
        card1=image;
      } else {
        var n1=card1.getAttribute('n');
        var n2=image.getAttribute('n');
        n1=n1%13;
        n2=n2%13;
        click_ok=false;
        if (n1==n2) {
          setTimeout(clear,1000,card1);
          setTimeout(clear,1000,image);
        } else {
          setTimeout(turn,2000,card1);
          setTimeout(turn,2000,image);
        }
        card1='';
      }
    }
  }
  function clear(image) {
    image.src='cards/0.png';
    click_ok=true;
  }
  function turn(image) {
    image.src='cards/back.png';
    click_ok=true;
  }
</script>
</body>