Morphing Fullscreen Hamburger Navigation With JavaScript And CSS3

A high-performance morphing navigation concept that reveals a fullscreen navigation menu as you click/tap on the hamburger toggle button. Built with plain JavaScript and CSS/CSS3.

How to use it:

Create the hamburger menu toggle button.

<div id="nav-bg" class="btn"></div>
<div id="toggle-btn" class="btn">
  <span></span>
  <span></span>
  <span></span>
</div>

Insert the navigation menu into your main content.

<div class="wrapper">
  <nav>
    <ul>
      <li><a class="link" href="#">Home</a></li>
      <li><a class="link" href="#">About</a></li>
      <li><a class="link" href="#">Contact</a></li>
    </ul>
  </nav>
  
  <div id="content">
    More content here
  </div>
</div>

The CSS styles for the navigation background.

#nav-bg {
  transform-origin: center center;
  transition: transform .3s;
  transform: translate(var(--translate-x), var(--translate-y)) scale(var(--scale));
  will-change: transform;
  pointer-events: none;
}

Style the toggle button.

.btn {
  position: fixed;
  height: calc(var(--btn-size)*1px);
  width: calc(var(--btn-size)*1px);
  bottom: calc((var(--offset-value))*1px);
  left: calc(var(--offset-value)*1px);
  /*left: calc(50% - (var(--btn-size)/2*1px)); if you wish to center it */
  border-radius: 50%;
  background: #fafafa;
  cursor: pointer;
  margin: 0;
  padding: 0 15px;
  border: none;
  z-index: 100;
  user-select: none;
  -webkit-tap-highlight-color: rgba(0,0,0,0);
}
#toggle-btn {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  color: var(--green);
  /*box-shadow: 0 6px 12px rgba(0,0,0,.1);*/
  transition: transform .3s;
}
#toggle-btn span {
  position: relative;
  width: 100%;
}
#toggle-btn span {
  margin-top: -4px;
}
#toggle-btn span + span {
  margin-top: 8px;
}
#toggle-btn span:before,
#toggle-btn span:after {
  content: '';
  position: absolute;
  top: 0;
  background: currentColor;
  opacity: .8;
  height: 100%;
  width: 50%;
  height: 4px;
  transition: .25s cubic-bezier(.6,0,.3,1);
  transform-origin: center center;
}
#toggle-btn span:before {
  left: 0;
  border-radius: 3px 0 0 3px;
}
#toggle-btn span:after {
  right: 0;
  border-radius: 0 3px 3px 0;
}
#toggle-btn.shown span:nth-of-type(1):before {
  transform: translate3d(3px, 3.5px, 0) rotate(45deg);
}
#toggle-btn.shown span:nth-of-type(1):after {
  transform: translate3d(-3px, 3.5px, 0) rotate(-45deg);
}
#toggle-btn.shown span:nth-of-type(3):before {
  transform: translate3d(3px, -3.5px, 0) rotate(-45deg);
}
#toggle-btn.shown span:nth-of-type(3):after {
  transform: translate3d(-3px, -3.5px, 0) rotate(45deg);
}
#toggle-btn.shown span:nth-of-type(2):before,
#toggle-btn.shown span:nth-of-type(2):after {
  opacity: 0;
}
#toggle-btn.shown span:nth-of-type(2):before {
  transform: translateX(-200%);
}
#toggle-btn.shown span:nth-of-type(2):after {
  transform: translateX(200%);
}
#toggle-btn.shown:before {
  transform: scale(.6);
  transition: .2s;
}
#toggle-btn:before {
  content: '';
  transition: .2s .2s;
  position: absolute;
  top: 3px;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,.1);
  border-radius: inherit;
  filter: blur(5px);
  z-index: -2;
}
#toggle-btn:after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border-radius: inherit;
  background: #fafafa;
  z-index: -1;
}

The main CSS for the navigation menu.

nav {
  width: 100%;
  height: 100%;
  background: transparent;
  position: fixed;
  top: 0;
  left: 0;
  overflow: hidden;
  display: flex;
  z-index: 200;
  pointer-events: none;
}
nav ul {
  margin: auto;
  pointer-events: auto;
  text-align: center;
}
nav li {
  font-size: 30px;
  color: #212121;
  user-select: none;
  transform: translate(-20px,20px) scale(.9);
  transition: 0s;
  opacity: 0;
  visibility: hidden;
  will-change: transform;
}
nav li + li {
  margin-top: 30px;
}
#toggle-btn.shown ~ .wrapper nav li {
  transform: none;
  opacity: 1;
  visibility: visible;
  transition: .35s cubic-bezier(.4,2.08,.55,1);
}
#toggle-btn.shown ~ .wrapper nav li:nth-child(1) {
  transition-delay: .15s;
}
#toggle-btn.shown ~ .wrapper nav li:nth-child(2) {
  transition-delay: .125s;
}
#toggle-btn.shown ~ .wrapper nav li:nth-child(3) {
  transition-delay: .1s;
}

The main JavaScript.

var elem = document.querySelector('#nav-bg'),
    toggleBtn = document.querySelector('#toggle-btn'),
    elemH = elem.getBoundingClientRect().height,
    elemW = elem.getBoundingClientRect().width;
var open = false;
var scale = undefined,
    offsetX = undefined,
    offsetY = undefined;
var calculateValues = function calculateValues() {
  var w = window.innerWidth;
  var h = window.innerHeight;
  //const cssStyles = getComputedStyle(elem);
  //const offsetValue = Number(cssStyles.getPropertyValue('--offset-value'));
  var offsetValue = Number(getComputedStyle(elem).getPropertyValue('--offset-value'));
  //  Offsets to center the circle
  offsetX = w / 2 - elemW / 2 - offsetValue;
  offsetY = h / 2 - elemH / 2 - offsetValue;
  // Good old pythagoras
  var radius = Math.sqrt(Math.pow(h, 2) + Math.pow(w, 2));
  scale = radius / (elemW / 2) / 2 + .1; // Add '.1' to compensate for Safari sub pixel blur issue
  return scale;
};
var openMenu = function openMenu() {
  elem.style.setProperty("--translate-x", offsetX + 'px');
  elem.style.setProperty("--translate-y", '-' + offsetY + 'px');
  elem.style.setProperty("--scale", scale);
};
var closeMenu = function closeMenu() {
  elem.style.setProperty("--scale", 1);
  elem.style.setProperty("--translate-x", 0);
  elem.style.setProperty("--translate-y", 0);
};
var animateMenu = function animateMenu() {
  open ? openMenu() : closeMenu();
};
var toggleMenu = function toggleMenu() {
  open = !open;
  animateMenu();
  toggleBtn.classList.toggle('shown');
};
var resizeHandler = function resizeHandler() {
  window.requestAnimationFrame(function () {
    calculateValues();
    animateMenu();
  });
};
calculateValues();
//toggleBtn.onclick = toggleMenu;
toggleBtn.addEventListener('click', toggleMenu, false);
window.addEventListener("resize", resizeHandler, false);