Tachyons CSS Library
Typemill uses the CSS library Tachyons. If you want to use the library for your theme, then you can activate it in the header like this:
<html>
<head>
<title>title</title>
....
....
{% block stylesheets %}
<link rel="stylesheet" href="{{ base_url }}/themes/mytheme/css/style.css" />
{{ assets.activateTachyons() }}
{{ assets.renderCSS() }}
{% endblock %}
</head>