<html lang="en">
<head>
  <title>CS:GO Case Opening Animation</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
  <script src="http://cdnjs.cloudflare.com/ajax/libs/jquery-easing/1.3/jquery.easing.min.js"></script>
  <link rel="stylesheet" href="style.css">
</head>
  <body>
    <div class="container-fluid">
      <div class="row">
        <button type="button" id="openCase" class="btn btn-info copenbtn"> OPEN </button>
        <div class="container-fluid caseOpeningArea">
          <div class="row">
            <div  class="container animationAreaItems">
              <div class="row">
                <div class="row text-center flex-nowrap mx-auto">
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div id="itemBoxAn itemBoxAnW" class="itemBoxAn itemBoxAnW"><img src="skins/Karambit Gold.webp" alt="">    </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                    <div class="itemBoxAn">  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
        <div id="test"></div>
      </div>
    </div>
  </body>
</html>
body {
  /*background: grey;*/
  background-repeat: no-repeat;
  background-size: cover;
  min-height: 100%;
  height: 100% !important;
}

#test{
  width: 100px;
  height: 80px;
  color: orange;
  margin: 0 auto;
  display:block;
  background: orange;
}

#openCase {
  float: none;
  margin: 0 auto;
  margin-top: 20px;
}

.copenbtn:focus, .copenbtn:active {
  outline: none !important;
  box-shadow: none !important;
}

.caseOpeningArea {
  margin-top: 20px;
}

.itemBoxAn {
  border-radius: 0px !important;
  border: none !important;
  margin-left: 3px;
  margin-top: 5px;
  width: 150px;
  height: 165px;
  background: cyan !important;
  position: relative;
}

.itemBoxAnW {
  border-radius: 0px !important;
  border: none !important;
  margin-left: 3px;
  margin-top: 5px;
  width: 150px;
  height: 165px;
  position: relative;
  background: black !important;
}

.itemBoxAnW img{
  width: 150px;
  height: 165px;
  position: relative;
}

.animationAreaItems {
  width: 100%;
  min-height: 180px;
  max-height: 180px;
  height: 180px !important;
  position: relative;
  text-align: center;
  display: inline-block;
  overflow: hidden;
  white-space: nowrap;
  border: 2px solid red;
}

.animationAreaItems:before {
  content: "";
  position: absolute;
  z-index: 1;
  top: 0;
  bottom: 0;
  left: 48%;
  border-style: solid;
  border-width: 0 20px 20px 20px;
  border-color: transparent transparent #ff0000 transparent;
}

.animationAreaItems:after {
  content: "";
  position: absolute;
  z-index: 1;
  top: 0;
  bottom: 0;
  left: 48%;
  border-style: solid;
  border-width: 20px 20px 0 20px;
  border-color: #ff0000 transparent transparent transparent;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js