Pure Hamburger Menu, no JS

by Faisal Khan Janjua

HTML

<h1>Your Content</h1>
<div class="outer-menu">
  <input class="checkbox-toggle" type="checkbox" />
  <div class="hamburger">
    <div></div>
  </div>
  <div class="menu">
    <div>
      <div>
        <ul>
          <li><a href="#">About</a></li>
          <li><a href="#">Products</a></li>
          <li><a href="#">Blog</a></li>
          <li><a href="#">Contact</a></li>
        </ul>
      </div>
    </div>
  </div>
</div>

CSS

@import url('https://fonts.googleapis.com/css?family=Pacifico|Open+Sans:300');
.flex-center {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-box-pack: center;
      -ms-flex-pack: center;
          justify-content: center;
}
* {
  box-sizing: border-box;
  font-family: 'Open Sans', sans-serif;
  font-weight: 300;
}
a,
a:visited,
a:hover,
a:active {
  color: inherit;
  text-decoration: none;
}
h1 {
  font-family: 'Pacifico', cursive;
  font-weight: 400;
  font-size: 3em;
  text-align: center;
}
.outer-menu {
  position: fixed;
  top: 10vh;
  left: 0;
  z-index: 1;
}
.outer-menu .checkbox-toggle {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 2;
  cursor: pointer;
  width: 60px;
  height: 60px;
  opacity: 0;
}
.outer-menu .checkbox-toggle:checked + .hamburger > div {
  -webkit-transform: rotate(135deg);
          transform: rotate(135deg);
}
.outer-menu .checkbox-toggle:checked + .hamburger > div:before,
.outer-menu .checkbox-toggle:checked + .hamburger > div:after {
  top: 0;
  -webkit-transform: rotate(90deg);
          transform: rotate(90deg);
}
.outer-menu .checkbox-toggle:checked + .hamburger > div:after {
  opacity: 0;
}
.outer-menu .checkbox-toggle:checked ~ .menu {
  pointer-events: auto;
  visibility: visible;
}
.outer-menu .checkbox-toggle:checked ~ .menu > div {
  -webkit-transform: scale(1);
          transform: scale(1);
  -webkit-transition-duration: .75s;
          transition-duration: .75s;
}
.outer-menu .checkbox-toggle:checked ~ .menu > div > div {
  opacity: 1;
  -webkit-transition: opacity 0.4s ease 0.4s;
  transition: opacity 0.4s ease 0.4s;
}
.outer-menu .checkbox-toggle:hover + .hamburger {
  box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.1);
}
.outer-menu .checkbox-toggle:checked:hover + .hamburger > div {
  -webkit-transform: rotate(225deg);
          transform: rotate(225deg);
}
.outer-menu .hamburger {
  position:...