I'm having trouble wrapping my brain around the strategy for how to use the `form-control` class offered by Bootstrap.

On one hand I have this rather bland comment from the Bootstrap documentation:

> 
> Textual form controls—like inputs, selects, and textareas—are styled with the .form-control class. Included are styles for general appearance, focus state, sizing, and more.
> 
> 
> 

Ref: <https://getbootstrap.com/docs/4.0/components/forms/#form-controls>

While on the other hand I have rather in-the-weeds code to look at:

```
.form-control {
  display: block;
  width: 100%;
  height: $input-height;
  padding: $input-padding-y $input-padding-x;
  // ... 40-some lines elided ...
}

```

ref: <https://github.com/twbs/bootstrap/blob/275cd7f91eed9f4051d85c295e5c14ef08937804/scss/_forms.scss>

My question: How can I holistically approach modifying existing code or writing new code with `form-control`.