Vertically centering navbar-collapse button - html

Question

I have a navbar with a logo that resizes as the user scrolls down.
This also resizes the navbar, making it shorter.
How do I get the collapse-button (#nav-btn) to center vertically regardless of the height of the navbar?
<nav class="navbar navbar-inverse navbar-toggleable-md fixed-top">
<button id="nav-btn" class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarDiv" aria-expanded="false" aria-label="Toggle navigation">
<span id="hamburger-icon"class="navbar-toggler-icon"></span>
</button>
<div class="nav-container text-center">
<a class="navbar-brand" href="#"><img id="navbar-logo" src="Images/logo.png" style="width:150px"></a>
</div>
<div class="collapse navbar-collapse" id="navbarDiv">
<div>
<ul class="navbar-nav mr-auto text-center">
<li class="nav-item">
<a class="nav-link" href="#home" >Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#about-us" >About</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#pricing" >Pricing</a>
</li>
</ul>
</div>
</div>
</nav>
CSS
/***** NAVBAR *****/
.navbar {
font-size: 25px;
padding: 5px;
padding-left: 8vw;
background-color: rgba(31, 31, 31, 0.5)
}
.nav-link {
font-weight: 500;
}
#nav-btn {
border: 1px solid white;
}

Answer 1

One way you can do it is give the #nav-btn absolute position.
Since it's inside a relative positioned element, it's gonna be absolute positioned relative to it's parent.
Now you can give it top: calc(50% - <half-of-it's-own-height>);
it'll position your button in 50% of it's parent and reduce half of it's height to fully vertical align it to center.
example for height 20px:
CSS
#nav-btn {
position: absolute;
height: 20px;
top: calc(50% - 10px);
}