I want to vertically center some of my elements

The easiest way to vertically center elements is to add a few properties to its parent. You need add display :flex and align-items:center.

HTML

<section class="flex-center">
  <div>bob</div>
</section>

CSS

.flex-center{
  display: flex;
  align-items: center;
  justify-content: center;
}

To have a quick play go to codepen.