We don't really know what this is. Is it performance art? A rag-tag hipster flash-mob? Is it actually a dance class? In any event, it's called Critical Ass, they've made this awesome video, and they're taking donations for an open-to-the-public dance class which will also "play with new ideas for performance" and happen on "select Sundays in September and October" in Dolores Park. If nothing else, you should be on the lookout for a gang of people dressed in spandex and brightly colored sunglasses invading one hill or other, and sweating off a few calories to some electronic music. [via Uptown Almanac]