Horizontal toggle menu

HTML

<nav class="nav">
  <button class="btn btn-menu" id="btn">Menu</button>
</nav>

CSS

.nav {
  width: 25%;
  height: 800px;
  background-color: #421;
}
.nav-min {
  width: 10% !important;
}

JavaScript

$('#btn').click(function() {
  $('.nav').toggleClass('nav-min');
});