The press screenings at the Cannes Film Festival typically end with a round of polite applause, scattered boos, or a schizoid mix of both; far rarer are the sounds of actual whooping and hollering. But Leos Carax’s “Holy Motors” bucked the trend on Tuesday night, playing to the most wildly enthusiastic cheers of the festival and igniting a storm of critical excitement on Twitter, with many journalists hailing it as the boldest pic to play in competition so far.“A holy mess of nutso go-for-broke filmmaking — wild, surreal and fully committed,” tweeted GQ’s Logan Hill. “Best of Cannes thus far, Carax’s ‘Mulholland Dr.,’ ” said the Village Voice’s Aaron Hillis. “Just mad enough to win the Palme d’Or,” in the estimation of the Guardian’s Peter Bradshaw. Reactions were harder to gauge during the actual screening of Carax’s uncategorizable whatsit, a mad, arrestingly wacky mystery tour centered around a man (Lavant’s longtime collaborator Denis Lavant) in a limousine, keeping a series of exceedingly strange appointments. Periodically the silence in the theater was broken by laughs and gasps, triggered by an extended glimpse of full-frontal nudity or a sudden burst of frenzied violence, but Cannes audiences are used to those sorts of triggers, often the signature of provocateurs like Lars von Trier and Gaspar Noe. What they aren’t so used to: sex scenes pantomimed in motion-capture spandex. Georges Franju references. An intermission scored by a band of accordionists. Kylie Minogue and Eva Mendes. A movie this certifiably nuts can’t please everyone, but while there was a smattering of boos as the credits began to roll, they were immediately drowned out by sustained waves of rapturous applause. As fitting a title as “Holy Motors” turns out to be, Carax’s first film in 13 years might well have stolen the moniker of Alain Resnais’ far less unhinged competition entry: You ain’t seen nothin’ yet.