<h2>My close button</h2>
<a href="#" class="close-button"></a>

.close-button {
  @size: 50px;
  height: @size;
  width: @size;
  position: relative;
  box-sizing: border-box;
  line-height: @size;
  display: inline-block;

  &:before, &:after {
    @width: 50px;
    @height: 10px;
    transform: rotate(-45deg);
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    margin-top: -@height/2;
    margin-left: -@width/2;
    display: block;
    height: @height;
    width: @width;
    background-color: #fff;
    transition: all 0.2s ease-out;
  }

  &:after {
    transform: rotate(45deg);
  }

  &:hover {

    &:before, &:after {
      transform: rotate(0deg);
    }
  }
}

body {
  color: #fff;
  font-family: arial, sans-sarif;
  background-color: #333;
  text-align: center;
}
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External CSS

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External JavaScript

  1. //cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js