<script>
  var arr=[12,52,38,26];
  var s1="<img src='cards/back.png' n='";
  var s2="' onClick='card_clicked(this);'>";
  for (var i=0; i<4; i++) {
    document.write(s1 + arr[i] + s2);
  }
  var card1='';
  function card_clicked(image) {
    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;
      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';
  }
  function turn(image) {
    image.src='cards/back.png';
  }
</script>