Oh-Flex Docs
Buttons
<button f-button clear f-primary>Button</button>
<button f-button>Button</button>
<button f-button-primary>Button</button>
<button f-button-dark>Button</button>
<button f-button-dark round>Round Button</button>
<button f-button-inverse f-bg-green-700 f-hover-zoom>Colored Button w/ Zoom</button>
<button f-button-inverse f-box-shadow-1 f-t-18px f-h-min-60px f-p-14px f-p-r-30px f-p-l-30px f-bg-pink-700 f-hover-fade>Mega Button!</button>
Source: _button.scss, line 21

Only want the button features of Oh-flex?

<link href="https://unpkg.com/oh-flex/lib/chunks/_button.css" rel="stylesheet" />
Source: _button.scss, line 158