In January this year (yes, I actually checked before posting about something) Alec brought us news of Fotonica - a first-person free running game that was played via Unity in a browser. Some things have changed since then, and the game is now downloadable for Mac or Windows, playable in full screen, along with a 'pay what you want' offer if you'd like to give the developers, Santa Ragione, some actual real money.
You don't have to pay what you want, either. You can just torrent either version for free, the .torrent file available directly from the site. And if you do pay, they ask that you make your payment over the £1.50/$2 mark, otherwise it'll all get eaten up in Paypal fees.
It's a remarkable game, and unlike anything else I've played. Definitely worth checking out. And then perhaps throwing money toward Santa Ragione. Here's a trailer: