Котик Антон

<div id="sidebar" class="nav-collapse hide-left-bar">
   ...
</div>
<section id="main-content" class="merge-left">
   ...
</section>

#main-content {
    margin-left: 240px;
    -webkit-transition: all .3s ease-in-out;
    -moz-transition: all .3s ease-in-out;
    -o-transition: all .3s ease-in-out;
    transition: all .3s ease-in-out;
}

.merge-left {
    margin-left: 0px !important;
}

#sidebar {
    width: 240px;
    height: 100%;
    position: fixed;
    background: #32323a;
    -webkit-transition: all .3s ease-in-out;
    -moz-transition: all .3s ease-in-out;
    -o-transition: all .3s ease-in-out;
    transition: all .3s ease-in-out;
}

.hide-left-bar {
    margin-left: -240px !important;
    -webkit-transition: all .3s ease-in-out;
    -moz-transition: all .3s ease-in-out;
    -o-transition: all .3s ease-in-out;
    transition: all .3s ease-in-out;
}

&-btn {
    .btn_cubic();
    .btn_cubic--orange();
    ...
}

.btn_cubic {
    ...
}

.btn_cubic--orange {
    ...
}

.main
{
	height: 300px;
	width: 100%;
	background-color: #c6c6c6;
}

.top, .top::after
{
  display: block;
  width: 200px;
  height: 200px;
}

.top 
{
  margin: 0 auto;
  position: relative;
  background-color: #6a56ff;
  top: 50px;
  left: 50px;
}

.top::after 
{
  content: '';
  position: absolute;
  background-color: #ffcb56;
  top: -50px;
  left: -50px;
}

var e = Array.prototype.slice.call(document.getElementById("values_list").getElementsByTagName("li"));
e.forEach(function(t) {
    t.addEventListener("mouseover", function() {
        e.forEach(function(e) {
            e.className = e.className.replace(/\bactive\b/, "")
        });
        var t = this;
        t.className += " active",
        document.getElementById("user_title").innerHTML = t.getAttribute("data-title"),
        document.getElementById("user_value").innerHTML = t.getAttribute("data-value"),
        t.getAttribute("data-caps") ? document.getElementById("user_value").style.textTransform = "lowercase" : document.getElementById("user_value").style.textTransform = "capitalize"
    })
})