As the Biennale reaches full speed, with huge crowds elbowing to see art, several countries are getting their first real moments in the sun. Turkey has its own pavilion this year for the first time, with a show by the artist Huseyin Alptekin called “Don’t Complain.” (A good rejoinder to anyone here moaning about sore feet or a hangover with the grandeur of St. Mark’s Cathedral rising in the background.) Mexico also made its official debut, renting a labyrinthine Gothic palazzo near the Rialto Bridge that looks like something out of a Tolkien fever dream, with a high interior courtyard flanked by a winding stone staircase. The exhibition, by Rafael Lozano-Hemmer, is the opposite of the don’t-touch art that fills most of this city. Every piece requires some kind of participation. In one room, you stand before a projector that throws your shadow 20 feet high on a wall. As you get “bigger,” a radio signal is directed toward you and you become a living antenna, causing crackly AM radio sounds to issue from speakers. The frequency you are channeling is projected on your shadow in red letters. The Mexican pavilion, where an epic three-day party has drawn hundreds of visitors, suffered a devastating blow before the show opened. One of its two curators, Príamo Lozada, accidentally fell from a third-story window of a building several days ago after arriving to prepare the show, and he has been hospitalized in a coma. But Bárbara Perea, the show’s other curator, said on Friday night that she had received news that his condition is improving and he is expected to recover.