JSFiddle - React, Tailwind, and code Playground

HTML

<body onload = "generateFaces()">
        <h2>Matching Game</h2>
        <p>Click on the extra smile on the left</p>
        <div id="leftSide"></div>
        <div id="rightSide"></div>
    </body>

CSS

img {
                position: absolute;
            }

            div {
                position: absolute;
                width: 500px;
                height: 500px;
            }

            #rightSide {
                left: 500px;
                border-left: 1px solid black;
            }

JavaScript

var numberOfFaces = 5;
 var theLeftSide = document.getElementById("leftSide");
 var theRightSide = document.getElementById("rightSide");

 function generateFaces() {
     for (var i = 0; i <= numberOfFaces; i++) {
         new_img = document.createElement("img");
         new_img.src = "http://images.clipartpanda.com/happy-face-black-and-white-018721-glossy-black-icon-symbols-shapes-smiley-face1.png";
         new_img.style.height = "48px";
         new_img.style.width = "48px";
         new_img.style.top = String(Math.floor(Math.random() * 400)) + "px";
         new_img.style.left = String(Math.floor(Math.random() * 400)) + "px";
         theLeftSide.appendChild(new_img);
     }

     // Clone all images to right side
     leftSideImages = theLeftSide.cloneNode(true);
     leftSideImages.removeChild(leftSideImages.lastChild);
     theRightSide.appendChild(leftSideImages);
 }

 //generateFaces()

 var theBody = document.getElementsByTagName("body")[0];

 theBody.onclick = function gameOver() {
     alert("Game Over!");
      while (theLeftSide.firstChild) {
         theLeftSide.removeChild(theLeftSide.firstChild);
     }

     while (theRightSide.firstChild) {
         theRightSide.removeChild(theRightSide.firstChild);
     }
      generateFaces();
 };

 theLeftSide.lastChild.onclick = function nextLevel(event) {
     // remove child nodes
     while (theLeftSide.firstChild) {
         theLeftSide.removeChild(theLeftSide.firstChild);
     }

     while (theRightSide.firstChild) {
         theRightSide.removeChild(theRightSide.firstChild);
     }

     // new nodes
     event.stopPropagation();
     numberOfFaces += 5;
     generateFaces();
 };