simon.js

let gameSeq=[];
let userSeq=[];

let btns=["yellow","red","purple","green"];

let h2=document.querySelector("h2");
let started=false;
let level=0;
document.addEventListener("keypress",function(){
   if(started==false)
   {
    console.log("game is started");
    started=true;
    levelUp();
   }
});
function gameFlash(btn){
btn.classList.add("flash");
setTimeout(function(){
    btn.classList.remove("flash");
},250);
}
function userflash(btn){
    btn.classList.add("userflash");
    setTimeout(function(){
        btn.classList.remove("userflash");
    },250);
    }
function levelUp(){
    userSeq=[];
    level++;
    h2.innerText= `Level ${level}`;

    let randIdx=Math.floor(Math.random()*3);
    let randColor=btns[randIdx];
    let randBtn=document.querySelector(`.${randColor}`);
    gameSeq.push(randColor);
    console.log(gameSeq);
    //random button is chosen
    gameFlash(randBtn);
}
function checkAns(idx){
if(userSeq[idx]===gameSeq[idx]){
  if(userSeq.length==gameSeq.length){
    setTimeout(levelUp,1000);
   
  }
}
else
{
    h2.innerHTML= `Game over! Your score was <b>${level}</b><br> Press any key to start.`;
    document.querySelector("body").style.backgroundColor="red";
    setTimeout(function(){
        document.querySelector("body").style.backgroundColor="white";
    },150);
    reset();
}
}

function btnPress(){
   let btn=this;
   userflash(btn);
   userColor=btn.getAttribute("id");
   userSeq.push(userColor);
   checkAns(userSeq.length-1);
}
let allBtns=document.querySelectorAll(".btn");
for(btn of allBtns){
    btn.addEventListener("click",btnPress);
}
function reset(){
    started=false;
    gameSeq=[];
    userSeq=[];
    level=0;

}