app.js

let gameSeq=[];
let userSeq=[];
let btnlist=["first","second","third","fourth"];
let started=false;
let h3=document.querySelector('h3');
document.addEventListener("keypress",function(){
    if(started==false){
        started=true;  
         game();
    }
});
let level=0;
function game(){
    level++;
    userSeq=[];
    h3.innerText=`LEVEL ${level}`;
    let btnidx=Math.floor(Math.random()*3);
    let btn=document.querySelector(`.${btnlist[btnidx]}`);
    gameSeq.push(btnlist[btnidx]);
    gameflash(btn);

}
function gameflash(btn){
   
    btn.classList.add("gameflash");
    setTimeout(function(){
        btn.classList.remove("gameflash");
    },200);
}
function userflash(btn){
   
    btn.classList.add("userflash");
    setTimeout(function(){
        btn.classList.remove("userflash");
    },200);
}
function btnclick(){
    let btn=document.getElementById(this.id);
    userSeq.push(`${this.id}`);
    setTimeout(userflash(btn),3000);
    
    checkans();
}
function checkans(){
    let idx=userSeq.length-1;
    if(gameSeq[idx]!=userSeq[idx]){
        h3.innerText=" WRONG MOVE GAME OVER!!";
        document.querySelector("body").style.backgroundColor="red";
        setTimeout(function(){
            document.querySelector("body").style.backgroundColor="white";  
            h3.innerHTML=`YOUR SCORE IS <b>${level} </b> <br> ENTER ANY KEY TO RESTART THE GAME`;
            reset();
        },1000);
       // 
        
        
    }
    else if(gameSeq.length==userSeq.length){
        setTimeout(game,1000); 
    }
}
let btns=document.querySelectorAll('.boxes');

for(let btn of btns){
    
    btn.addEventListener("click",btnclick);
    
}
function reset(){
    gameSeq=[];
    userSeq=[];
    level=0;
    started=false;
}