Most of your rendering will go in .view
.view is a absolute positioned div that fills the screen, minus room for the header, tabs and tray if required (that's what .has-tray does).
.content provides a fixed width container. .panel provised fixed width and white background.
<div class="view">
<div class="splash">
</div>
</div>
Full area of view is given a white background, some padding, and permitted to scroll. Intended to be flowed with text content for long-form reading
<div class="view">
<div class="content">
</div>
</div>
<div class="view">
<div class="panel">
</div>
</div>
<div class="view">
<div class="empty">
</div>
</div>
Actions, Selector, Dataset
<div class="view">
<div class="actions">
</div>
<div class="selector">
</div>
<div class="dataset">
</div>
</div>
Actions, Form
<div class="view">
<div class="actions">
</div>
<div class="panel">
<div class="form">
</div>
</div>
</div>