The artsy technology geeks at Eyebeam really outdid themselves with last night's sold-out "MIXER Underground" by turning their warehouse-size Chelsea space into an elaborate labyrinth and rock club. The place was swarming with giddy artists who must have spent weeks building their massive DIY creation, and the enthusiasm was contagious, evoking the spirit of the old Rubulad parties when they started in pre-gentrified South Williamsburg. There was a robotic bartender hidden away behind a fake closet, and the maze itself was filled with video installations, living sculptures, human rats, and electronic insects. On a high stage at the far end of the room, Roxy Cottontail and Judi Chicago churned out frenetic dance music, and vendors roamed the crowd with coolers of cheap beer. What more could you ask for? (Actually, some hash brownies would have been nice.) The parties are thrown quarterly, so check their website again in the winter if you want in.