anchor.diff:  
   <h3>Current game id: <span id="game-id"></span></h3>
   <h3>Current score: <span id="game-score"></span></h3>
  -
  +<h3>Frame number: <span id="game-frames"></span></h3>
  +<h3>Game over: <span id="game-over"></span></h3>
   <br/>
   
   <form id="knocked-pins-form">
  
positive.code:         .success(function(data){
            update_current_game_id(data.id);
            update_score();
            update_error_message("");
            console.log("Success on requesting POST '/games'. Created game with id: " + data.id);
          })
          .error(function(data){
  
negative.code: 
      function send_knocked_pins(knocked_pins){
        $.ajax({
            "url": "/games/"+current_game_id,
            "type": "PUT",
            "data": {"knocked_pins": knocked_pins},
            success: function (data, text) {
              update_score();
              clear_error_message();
              console.log("Success on requesting PUT '/games/" + current_game_id + " with body: {knocked_pins: " + knocked_pins + "}");
              $("#knocked-pins").val("");
            },
            error: function (request, status, error) {
              try {
                error_message = request.responseJSON.message;
              }
              catch(err) {
                error_message = "";
              }
              finally {
                update_error_message(error_message);
                console.error("Error on requesting PUT '/games/" + current_game_id + " with body: {knocked_pins: " + knocked_pins + "}");
                console.error(request);
              }
            }
        });
      }
  
      function update_error_message(message){
        if (!message) { message = "Server error." }
        $("#error-message").text(message);
      }
  
      function clear_error_message(){
        $("#error-message").text("");
      }
    })
  </script>
  