game.js

var gamePattern=[];
var userClickedPattern=[];
var buttonColours=["red", "blue", "green", "yellow"];
var level=0;
var started=false;

$(".btn").click(function(){
    var userChosenColour=$(this).attr("id");
    userClickedPattern.push(userChosenColour);
    playSound(userChosenColour);
    animatePress(userChosenColour);
    checkAnswer((userClickedPattern.length)-1);
});

$(".start").click(function(){
    if(!started){
        $("#level-title").html("Level "+level);
        nextSequence();
        started=true;
    }    
});

function nextSequence(){
    userClickedPattern.length=0;
    var randomNumber=Math.floor(Math.random()*4);
    var randomChosenColour=buttonColours[randomNumber];
    gamePattern.push(randomChosenColour);
    $("#"+randomChosenColour).fadeOut(100).fadeIn(100);
    playSound(randomChosenColour);
    level++;
    $("#level-title").html("Level "+level);    
}

function playSound(name){
    var audio=new Audio("sounds/"+name+".mp3");
    audio.play();
}

function animatePress(currentColor){
    $("#"+currentColor).addClass("pressed");
    setTimeout(function(){
        $("#"+currentColor).removeClass("pressed");
    },100);
}

function checkAnswer(currentLevel){
    if(gamePattern[currentLevel]===userClickedPattern[currentLevel]){
        console.log("Success");
        if(userClickedPattern.length===gamePattern.length){
            setTimeout(function(){
                nextSequence();
            },1000);
        }
    }
    else{
        console.log("failed");
        $("#level-title").html("Game Over! Press START key to Restart");
        playSound("wrong");
        $("body").addClass("game-over");
        setTimeout(function(){
            $("body").removeClass("game-over");
        },200);
        startOver();
    }

    function startOver(){
        level=0;
        gamePattern.length=0;
        started=false;
    }
}