Mobile-first responsive design with rem and em units. Built on top of normalize.css (removed < IE 11 fixes). Styles for Grid, Forms, Buttons, Navs, Navbar, Typography, Tables, Helpers, are available.
Source code is written in Stylus. Stylus and Sass are equally good in terms of features but I like Stylus syntax as it is more flexible, clean and JavaScript like.
Include the following code in <head> tag of your HTML file.
<link rel="stylesheet" href="https://cdn.rawgit.com/styli/styli/v0.1.0/css/styli.min.css"><!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title></title>
<meta name="description" content="">
<!-- Styli CSS -->
<link rel="stylesheet" href="https://cdn.rawgit.com/styli/styli/v0.1.0/css/styli.min.css">
</head>
<body>
<!--[if lt IE 11]>
<div class="bg-error bg-dark size-large">You are using a <strong>shitty</strong> browser. Please <a target="_blank" href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.</div>
<![endif]-->
<!-- Add your site or application content here -->
<h1>Hello, world!</h1>
</body>
</html>