JSFiddle - React, Tailwind, and code Playground

HTML

<body>

  <section id='score'>
    <div>
      SCORE<br>
      <strong>0</strong>
    </div>
  </section>



  <section id='board'>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
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  </section>


  <section id='over' class='invisible'>

  </section>

</body>

CSS

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 0;
}

section#score {
  width: 100%;
}

#board {
  width: 640px;
  height: 640px;
  margin: 1em auto;
}

#board  > div {    
  border: 1px solid black;
  float: left;
  width: 64px;
  height: 64px;
  position:relative;
}


section#score div {
  width: 10em;
  height: 3em;
  text-align: center;
  padding: 0.5em;
  background-color: rgba(211,211,211, 0.75);
  border: 1px solid lightgray;
  border-radius: 1px;
  box-shadow: 1px 1px 5px 1px lightgray;
  margin: 1em auto;
}




.furry {
  /* background-image: url('../images/furry.png'); */
  background-repeat: no-repeat;
  background-size: cover;
}
.furry:after {
  content: 'furry';
  position:absolute;
  right:0;
}
.coin {
  /* background-image: url('../images/coin.png'); */
  background-repeat: no-repeat;
  background-size: cover;
}
.coin:after {
  content: 'coin';
  position:absolute;
  right:0;
}

section#over {
  position: fixed;
  width: 100%;
  height: 100%;
  left: 0;
  top: 0;
  z-index: 1;
  padding: 10px;
  background-color: rgba(255, 255, 0, 0.75);
}

section#over pre {
  display: inline-block;
  width: 100%;
  text-align: center;
  font-size: 10px;
  font-weight: bolder;
  color: brown;
}

.invisible {
  display: none;
}

JavaScript

function Furry() {
  this.x = Math.floor(Math.random() * 10);
  this.y = Math.floor(Math.random() * 10);
  this.direction = "right";
} //constructor of furry
function Game() {
  this.board=document.querySelectorAll('#board div');
  this.furry = new Furry();
  this.coin = new Coin();
  this.score = 0;
} //constructor of game
Game.prototype.position = function(x, y) {
  return x + (y * 10);
} //method to constructor
Game.prototype.start = function() {
	this.board[this.position(this.coin.x, this.coin.y)].classList.add('coin');
  this.board[this.position(this.furry.x, this.furry.y)].classList.add('furry');
}
function Coin() {
  this.x = Math.floor(Math.random() * 10);
  this.y = Math.floor(Math.random() * 10);
}//constructor of coins which will be collected by fury

var Game = new Game();
Game.start();