Markup
<button class="m-btn [modifier class]">Button</button>
<button class="m-btn m-btn--primary [modifier class]">Button</button>
<button class="m-btn m-btn--warning [modifier class]">Button</button>
<button class="m-btn m-btn--danger [modifier class]">Button</button>
Source:
static/css/src/_m-btn.scss, line 1