"... What are the system requirements?: A web browser with Flash installed, on pretty much any computer purchased in the last few years. ..." from ~ http://glitch.com/
They also have a pretty clever approach to reaching users without Flash (from the article): Mobile apps are planned at some point, but Tiny Speck’s vision is not to port the entire game to the iPhone or Android devices. Rather, mobile apps would feature mini-games. Playing them would amp up your web game avatar’s abilities. Other options for mobile apps could include managing your in-game robot servants and participating in in-game auctions.
The idea (as I understand it) is to treat the game as this thing that you participate in in many different ways rather than a single distinct piece of software. Like an MMO with a dash of ARG[1], I suppose, though not really either. I think this is actually a really big idea, and the influence of Finite and Infinite Games[2] is apparent in almost every described detail.
[1]http://en.wikipedia.org/wiki/Alternate_reality_game [2]:http://en.wikipedia.org/wiki/Finite_and_Infinite_Games