Edit in JSFiddle

<div class="container">
  <label class="title">foobar</label>
  <p>hogehoge</p>
</div>
<div class="container light">
  <label class="title">light</label>
  <p>piyo</p>
</div>
<button type="button" class="btn">Normal</button>
<button type="button" class="btn primary">Primary</button>
<button type="button" class="btn success">Success</button>
<button type="button" class="btn warning">Warning</button>
<button type="button" class="btn error">Error</button>