<button class="mui-btn">
  <span class="mui-icon mui-icon-search"></span>
  Button
</button>
<button class="mui-btn mui-btn-primary">
  <span class="mui-icon mui-icon-search"></span>
  Button
</button>
<button class="mui-btn mui-btn-positive">
  <span class="mui-icon mui-icon-search"></span>
  Button
</button>
<button class="mui-btn mui-btn-negative">
  <span class="mui-icon mui-icon-search"></span>
  Button
</button>
<button class="mui-btn mui-btn-link">
  <span class="mui-icon mui-icon-left"></span>
  Button
</button>