This framework uses white-space, a way to add blank lines. It uses the heigt property for this. The value determines the height of the white space.
The white space in the blue area indicates the white space.
white-space-25
<div class="white-space-25"></div>
white-space-50
<div class="white-space-50"></div>
white-space-75
<div class="white-space-75"></div>
white-space-100
<div class="white-space-100"></div>
white-space-150
<div class="white-space-150"></div>
white-space-200
<div class="white-space-200"></div>
white-space-300
<div class="white-space-300"></div>
white-space-400
<div class="white-space-400"></div>
white-space-500
<div class="white-space-500"></div>
white-space-600
<div class="white-space-600"></div>