I'll just say that it's one of the coolest things I've played on PC lately, and that I can't wait to play the equally short sequel, Thirty Flights of Loving, that Blendo Games just released on their site and on Steam yesterday.
But seriously. Go download Gravity Bone. It's free. Spend 15 minutes playing it. Enjoy.
Gravity Bone [Blendo Official Site, Click "Gravity Bone" for free download]