https://github.com/Pauan/nulan (project page)
http://pauan.github.io/nulan/doc/tutorial.html (interactive tutorial in the browser)
Arguably, it improves upon Arc in many, many ways. :) Perhaps Arc's main advantage is that there are more people who use and maintain Arc. I'm sorry to say I've never used Nulan for anything, even though I'm suggesting it here.
