script.js

var blockBuzz = true,
    answerValue = 0,
    questionsJson,
    introClick = 1;

var onKeyPress = function(e) {
    if(e.keyCode > 48 && e.keyCode < 52) {
        triggerPlayer(e.keyCode - 48);
    }
};

var onDocumentClick = function(e) {

    if(introClick == 1) {
        try {
            switchOnLED(null);
        } catch(e) {}
        Array.prototype.forEach.call(document.querySelectorAll("#players input"), function(input) {
            input.readOnly = true;
        });
    }

    if(introClick < 7) {
        var elem = document.getElementById("column" + introClick).children[0];

        if(elem.classList.contains("highlight")) {
            var x = elem.offsetLeft + elem.offsetWidth / 2;
            var y = elem.offsetTop - elem.offsetHeight / 2;
            elem.children[1].style.transformOrigin = x + "px " + y + "px 0px";
            elem.classList.remove('highlight');
            elem.classList.add('visible');
            introClick++;
        }
        else {
            document.getElementById("column" + introClick).children[0].classList.add('highlight');
        }
    }

    if(introClick == 7) {
        setTimeout(function() {
            document.getElementById("board").classList.add("start");
        }, 1500);
    }

};

var onPlayerClick = function(e) {
    if(e.currentTarget.classList.contains("buzzed")) {
        e.currentTarget.children[1].textContent = parseInt(e.currentTarget.children[1].textContent, 10) + answerValue;
        e.currentTarget.classList.remove("buzzed");
        answerValue = 0;
        switchOnLED(null);
    }
    else {
        try {
            document.querySelector(".buzzed").classList.remove("buzzed");
            blockBuzz = false;
            switchOnLED(null);
        }
        catch(e) {}
    }
};

var onCardClick = function(e) {
    if(e.currentTarget.classList.contains("open")) {
       e.currentTarget.classList.remove("open")
       e.currentTarget.classList.add("show");
    }
    else if(e.currentTarget.classList.contains("show")) {
       e.currentTarget.classList.remove("show")
       e.currentTarget.classList.add("done");
    }
    else if(introClick >= 7) {
        var x = e.currentTarget.offsetLeft + e.currentTarget.offsetWidth / 2;
        var y = e.currentTarget.offsetTop + e.currentTarget.offsetHeight / 2;
        e.currentTarget.children[2].style.transformOrigin = x + "px " + y + "px 0px";
        e.currentTarget.classList.add("open");
        blockBuzz = false;
        answerValue = parseInt(e.currentTarget.children[0].textContent, 10);

        try {
            switchOnLED(null);
        }
        catch(e) {}

        try {
            document.querySelector(".buzzed").classList.remove("buzzed");
        }
        catch(e) {}
    }
};

var triggerPlayer = function(player_number) { // player_numbers: 1, 2, 3
    if(blockBuzz) {
        return;
    }

    blockBuzz = true;
    document.getElementById('bsound').play();
    document.getElementById("player" + player_number).classList.add("buzzed");

    switchOnLED(player_number-1);
}

document.onkeypress = onKeyPress;
document.getElementById("board").onclick = onDocumentClick;

Array.prototype.forEach.call(document.getElementById("players").childNodes, function(player) {
    player.onclick = onPlayerClick;
});

Array.prototype.forEach.call(document.querySelectorAll(".card"), function(card) {
    card.onclick = onCardClick;
});

loadQuestions();

// Ajax
function loadQuestions() {
  var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (xhttp.readyState == 4 && xhttp.status == 200) {
        questionsJson = xhttp.responseText;
    }
  }
  xhttp.open("GET", "data.json", true);
  xhttp.send();
}