<div class="body">

  <nav class="site-nav">
    <div class="container">
      <div class="navbar-mobile">
        <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-ex1-collapse">
          <div class="close">X</div>
          <span class="icon-bar bar-1"></span>
          <span class="icon-bar bar-2"></span>
          <span class="icon-bar bar-3"></span>
        </button>
      </div>

      <nav class="[ collapse navbar-collapse navbar-ex1-collapse ]">
        <ul class='navbar'>
          <li><a href="">Home</a></li>
          <li><a href="">About</a></li>
          <li><a href="">Contact</a></li>
          <li><a href="">Blog</a></li>
        </ul>
      </nav>

    </div>
  </nav>
  <!--- end nav -->

  <article class="content">
    <h1>Put our experience to work for you</h1>
    <p>
      The technicians at The Top Shop Auto Repair are ASE certified, specializing in Toyota and Lexus repair and electronic diagnostics. With 20 years of professional automotive experience, we work on all makes and models. From oil and filter changes to major engine repairs, you can count on us for affordable service.
    </p>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse pharetra metus non finibus malesuada. Donec sed felis eget sem convallis elementum eu vel est. Donec vulputate dictum massa. 
    </p>
  </article>
  
</div>
*, :before,:after {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

body {
  font-family: 'Source Sans Pro', sans-serif;
  font-weight: 200;
  font-size: 16px;   
  line-height: 1.458;
  background: #FeFeFe;
}

h1 {
  font-size: 2em;
  margin: 0;
  line-height: 1;
}

.body {
  -webkit-box-shadow: 0 0 20px 0 rgba(0,0,0,.3);
  box-shadow: 0 0 20px 0 rgba(0,0,0,.3);
  max-width: 320px;
  margin: 0 auto;
}

.navbar-brand, .sr-only {display: none;}

.navbar-toggle {
  display: block;
  position: relative;
  background: #dbdcdf;
  padding: 4px;
  cursor: pointer;
  border: 0px;
  margin: 0;
  border-radius: 0 0 12px 0;
  min-height: 50px;
  min-width: 50px;
  box-shadow: 1px 1px 2px 0 rgba(0,0,0,.2);
  outline: none;
  .icon-bar {
    background: #868d97;
    height: 6px;
    width: 30px;
    display: block;
    margin-top: 5px;
    border-radius: 3px;
    position: relative;
    transition: all .3s ease;
    &:first-of-type {
      margin-top: 0;
    }
    &:after {
      content: "";
      width: 6px;
      height: 6px;
      background: #868d97;
      position: absolute;
      right: -8px;
      border-radius: 3px;
    }
  }
}

.close {
  display: none;
  position: absolute;
  right: 12px;
  top: 12px;
  font-size: 24px;
  font-weight: 900;
  color: #d0112b;
  border: 4px solid #d0112b;
  padding: 2px;
  border-radius: 100%;
  width:  40px;
  height: 40px;
  line-height: 29px;
}

 .site-nav {
  background: #d0112b;
  border-radius: 0;
  border: none;
  margin: 0 auto;;
  width: 100%;
  font-size: 24px;
  font-weight: 700;
  color: #FFFFFF;
  text-transform: uppercase;
  overflow-y: visible;
  position: relative;
  max-height: 50px;
  max-width: 480px;
  box-shadow: 0 2px 1px 0 rgba(0,0,0,.1);
}

.navbar-mobile {
  display: inline-block;
  position: relative;
}

.collapse {visibility: hidden;}

.open {visibility: visible;}

.navbar {
  max-width: 50vw;
  position: absolute;
  top: 30px;
  z-index: 200;
}

ul {
  margin: 0;
  padding: 0;
}

.navbar li {
  text-align: left;
  display: block;
  min-height: 50px; 
  line-height: 50px;
  margin-left: 40px;
  a, a:visited {
    color: #868d97;
    text-decoration: none;
    &:hover {
      color: #d0112b;
    }
  }
}

.content {
  max-width: 480px;
  color: #FeFeFe;
  margin: 0 auto;
  background: #333;
  padding: 32px 20px;
  h1{ 
  color: #7d7d7d;
  }
}
View Compiled
$(document).ready(function() {
  
  $('.navbar-toggle').mouseenter(function() {
    if ($(this).hasClass('active')) {
    } else {
      $('.navbar-toggle').animate ({
          width: '60px',
          height: '60px'
        }, 200, function(){
          // anim complete
        });
    }
    });
  
  
    $('.navbar-toggle').mouseleave(function() {
      if ($(this).hasClass('active')) {} else {
    $('.navbar-toggle').animate ({
        width: '50px',
        height: '50px'
      }, 200, function(){
        // anim complete
      });
      }
  });
  
  
  
  
  
  $('.navbar-toggle').click(function() {
    var $this = $(this);
    
    if ($('.collapse').hasClass('open')) {
      $('.navbar > li').slideUp("fast");  
      $this.removeClass('active');
      $('.collapse').removeClass('open');  
      $this.animate ({
        width: '50px',
        height: '50px',
        borderBottomRightRadius: '12px'
      }, 200, function(){
        // anim complete
      });
      $('.close').hide('fast');
      setTimeout(function() {
        $this.children('.icon-bar').show("fast");
      }, 200);
    } 


    else {
      $this.delay("100").addClass('active');
      //$('.collapse').stop(true).slideDown("fast");
      $this.children('.icon-bar').hide();
      $this.delay("220").animate ({
        width: '300px',
        height: '275px',
        borderBottomRightRadius: '275px'
      }, 200, function(){
        // anim complete
      });
      setTimeout(function() {
        $('.navbar > li').slideDown("fast");
        $('.collapse').addClass('open');
        $('.close').show('fast');
      }, 500);
    }
  });
});

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

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