It's not that hard for a horror movie to jolt an audience. Most follow a formula: Darken the screen, threaten to populate the blank spaces with some kind of monster, fill the soundtrack with increasingly intensifying, droning music, and then, bang! Whatever happens next — be it a harmless kitty-cat leaping out from under a bed, or an actual thrill-killer smashing through a window — viewers jump out of their skins. Writer-director Ari Aster's supernatural thriller Hereditary handles the routine scary stuff reasonably well.