A week-long hacking session at Twitter HQ concluded today with a halloween costume party and a day of technology demos. In the photo above, Evan Williams sits in the middle of the room, in front of investor kingpin Ron Conway, to watch demos.

From infrastructure projects to robots, the range of demos was wide and the Tweets from participants were very enthusiastic. Will any of the hacks built this week see the light of day outside Twitter's headquarters? We can only hope so. Photo used by permission from @kris at Twitter.