Pure CSS Fold Out Navigation Menu

A HTML / CSS only navigation system that uses :checked selector to toggle an off-screen menu with a hamburger button.

How to use it:

Create a fake / hidden checkbox which is used as click reciever, so you can use the :checked selector on it.

<input type="checkbox">

Create three spans for the hamburger button.

<span></span>
<span></span>
<span></span>

Create the navigation menu.

<ul id="menu">
  <a href="#"><li>Home</li></a>
  <a href="#"><li>About</li></a>
  <a href="#"><li>Blog</li></a>
  <a href="#"><li>Contact</li></a>
</ul>

The entire html structure should be like this:

<nav>
  <div id="menuToggle">
    <input type="checkbox">
    <span></span>
    <span></span>
    <span></span>
    <ul id="menu">
      <a href="#"><li>Home</li></a>
      <a href="#"><li>About</li></a>
      <a href="#"><li>Blog</li></a>
      <a href="#"><li>Contact</li></a>
    </ul>
  </div>
</nav>

The CSS / CSS3 rules for the hamburger button.

#menuToggle {
  display: block;
  position: relative;
  top: 50px;
  left: 50px;
  z-index: 1;
  -webkit-user-select: none;
  user-select: none;
}
#menuToggle input {
  display: block;
  width: 33px;
  height: 28px;
  position: absolute;
  top: 0;
  left: 0;
  cursor: pointer;
  opacity: 0; /* hide this */
  z-index: 2; /* and place it over the hamburger */
}
/*
 * Just a quick hamburger
 */
#menuToggle span {
  display: block;
  width: 33px;
  height: 4px;
  margin-bottom: 5px;
  position: relative;
  background: #cdcdcd;
  border-radius: 3px;
  z-index: 1;
  transform-origin: 4px 0px;
  transition: transform 0.5s cubic-bezier(0.77, 0.2, 0.05, 1.0),  background 0.5s cubic-bezier(0.77, 0.2, 0.05, 1.0),  opacity 0.55s ease;
}
#menuToggle span:first-child { transform-origin: 0% 0%; }
#menuToggle span:nth-last-child(2) { transform-origin: 0% 100%; }
/* 
 * Transform all the slices of hamburger
 * into a crossmark.
 */
#menuToggle input:checked ~ span {
  opacity: 1;
  transform: rotate(45deg) translate(-2px, -1px);
  background: #232323;
}
/*
 * But let's hide the middle one.
 */
#menuToggle input:checked ~ span:nth-last-child(3) {
  opacity: 0;
  transform: rotate(0deg) scale(0.2, 0.2);
}
/*
 * Ohyeah and the last one should go the other direction
 */
#menuToggle input:checked ~ span:nth-last-child(2) {
  opacity: 1;
  transform: rotate(-45deg) translate(0, -1px);
}

The Primary CSS styles for the navigation menu.

/*
 * Make this absolute positioned
 * at the top left of the screen
 */
#menu {
  position: absolute;
  width: 300px;
  margin: -100px 0 0 -50px;
  padding: 50px;
  padding-top: 125px;
  background: #ededed;
  list-style-type: none;
  transform-origin: 0% 0%;
  transform: translate(-100%, 0);
  transition: transform 0.5s cubic-bezier(0.77, 0.2, 0.05, 1.0);
}
#menu li {
  padding: 10px 0;
  font-size: 22px;
}
/*
 * And let's fade it in from the left
 */
#menuToggle input:checked ~ ul {
  transform: scale(1.0, 1.0);
  opacity: 1;
}