In The Dark Knight, Joker (Heath Ledger) says, “As you know, madness is like gravity...all it takes is a little push.” In Todd Phillips’ Joker, madness is like a gas—it fills the space to which it is confined. But it’s also thin, ethereal, and lacks substance. The craft of the film—the cinematography, the score, the production design—along with Joaquin Phoenix’s magnetic, dedicated performance, is outstanding. Phillips has created an eye-catching, atmospheric take on Gotham, but he hasn’t done anything interesting with it. Instead, he’s content to push a bunch of hot-…