Responsive Fade In/Out Navigation In Pure CSS

This is a minimal responsive navigation that transforms the horizontal menu into a fullscreen toggle menu with fade in and out animations. Written in pure CSS/CSS3.

How to use it:

Create a normal header navigation for your cross-platform webpage.

<header class="header">
  <nav>
    <ul>
      <li><a href="#">Item 1</a></li>
      <li><a href="#">Item 2</a></li>
      <li><a href="#">Item 3</a></li>
      <li><a href="#">Item 4</a></li>
      <li><a href="#">Item 5</a></li>
    </ul>
  </nav>
</header>

Create the mobile menu toggle controls.

<input type="checkbox" class="menu-toggle" id="menu-toggle">
<div class="mobile-bar">
  <label for="menu-toggle" class="menu-icon">
    <span></span>
  </label>
</div>

The required CSS for the site navigation.

/**---- Fade-In/Out Effect ----**/
.menu-toggle:checked ~ .header {
  visibility: visible;
  opacity: 1;
  -webkit-transition-delay: 0s;
  transition-delay: 0s;
}
/**---- Header ----**/
.header {
	visibility: hidden;
	opacity: 0;
  position: fixed;
  top: 0;
  left: 0;
  padding-top: 60px;
  width: 100%;
  height: 100%;
  background-color: #E53935;
  overflow-y: scroll;
  text-align: center;
  color: #eee;
	-webkit-transition: opacity 300ms ease-in, visibility 0s ease-in 300ms;
	transition: opacity 300ms ease-in, visibility 0s ease-in 300ms;
}
.header nav,
.header ul {
  height: 100%;
}
.header li {
  border-bottom: 1px solid #eee;
}
.header a {
  display: block;
  padding: 35px;
  -webkit-transition: background-color 300ms ease-in;
  transition: background-color 300ms ease-in;
}
.header a:hover {
  background-color: #C62828;
}

The CSS for the mobile menu toggle controls.

/**---- Mobile Bar ----**/
.menu-toggle {
  display: none;
}
.mobile-bar {
  z-index: 10;
  position: fixed;
  top: 0;
  left: 0;
  padding: 0 25px;
  width: 100%;
  height: 60px;
  background-color: #E53935;
  -webkit-box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
}
/**---- Menu Icon ----**/
.menu-icon {
  display: block;
  position: relative;
  width: 25px;
  height: 100%;
  cursor: pointer;
  -webkit-transition: -webkit-transform 300ms ease-in;
  transition: -webkit-transform 300ms ease-in;
  transition: transform 300ms ease-in;
  transition: transform 300ms ease-in, -webkit-transform 300ms ease-in;
}
.menu-icon > span {
  display: block;
  position: absolute;
  top: 55%;
  margin-top: -0.3em;
  width: 100%;
  height: 0.3em;
  border-radius: 1px;
  background-color: #eee;
  -webkit-transition: -webkit-transform 300ms ease-in;
  transition: -webkit-transform 300ms ease-in;
  transition: transform 300ms ease-in;
  transition: transform 300ms ease-in, -webkit-transform 300ms ease-in;
}
.menu-icon > span:before,
.menu-icon > span:after {
  content: "";
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 1px;
  background-color: #eee;
  -webkit-transition: -webkit-transform 300ms ease;
  transition: -webkit-transform 300ms ease;
  transition: transform 300ms ease;
  transition: transform 300ms ease, -webkit-transform 300ms ease;
}
.menu-icon > span:before {
  -webkit-transform: translateY(-0.6em);
  transform: translateY(-0.6em);
}
.menu-icon > span:after {
  -webkit-transform: translateY(0.6em);
  transform: translateY(0.6em);
}
/**---- Menu Icon Effects ----**/
.menu-toggle:checked + .mobile-bar .menu-icon {
  -webkit-transform: rotate(45deg);
  transform: rotate(45deg);
}
.menu-toggle:checked + .mobile-bar span:before,
.menu-toggle:checked + .mobile-bar span:after {
  -webkit-transform: rotate(90deg);
  transform: rotate(90deg);
}

Create the magic in the CSS media queries.

@media (min-width: 720px) {
  .mobile-bar {
    display: none;
  }
  
  .header {
    z-index: 5;
    position: relative;
    left: 0;
    padding-top: 0;
    width: 100%;
    height: auto;
    overflow: auto;
    visibility: visible;
    opacity: 1;
  }
  .header li {
    display: inline-block;
    margin-right: -6px; /* fix the inline-block gap */
    border: none;
  }
  .header a {
    padding: 12px 45px;
  }
}