index.js

var start= false;
var level=0;

var buttonColors= ["red", "blue", "green", "yellow"];
var gamePattern= [];
var userClickedPattern= [];

$(document).keypress(function() {
  if (!start) {

    //3. The h1 title starts out saying "Press A Key to Start", when the game has started, change this to say "Level 0".
    $("#level-title").text("Level " + level);
    nextSequence();
    start = true;
  }
});

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





function nextSequence() {
  userClickedPattern = [];
  level++;
  $("#level-title").text("Level " + level);

  var randomNumber = Math.floor(Math.random() *4);
  var randomChosenColor= buttonColors[randomNumber];
  gamePattern.push(randomChosenColor);

  $("#"+ randomChosenColor).fadeIn(100).fadeOut(100).fadeIn(100);    //Animation

  var audio = new Audio("sounds/" + randomChosenColor + ".mp3");  //Audio
  audio.play();

}

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]) {   //last entered element matches

    //finished their sequence
    if (userClickedPattern.length === gamePattern.length){

      setTimeout(function () {
        nextSequence();
      }, 1000);

    }
  }
  else {
    playSound("wrong");

    $("body").addClass("game-over");
    setTimeout(function () {
      $("body").removeClass("game-over");
    }, 200);
    $("#level-title").text("Game Over. Press any Key to Restart.");
    startOver();
  }
}

function startOver(){
  level=0;
  gamePattern= [];
  start= false;
}