The Demonstrating Of Isaac

The Binding of Isaac, Ed McMillen and Florian Himsl's icky, ingenious Zeldalike now benefits from an online demo, hosted in the browser-based medium of Flash at Newgrounds.

It only includes two areas of the game and a few of the items and foes, so may struggle to convey the randomly-generated wonder/horror of this shooter/roleplayer/matricide curio, but if you're still confused about exactly what this game is, this will give you a broad sense of it.