‘T he world is changing. I can feel it – don’t you?” says black model Roxy (Adriane McLean), before donning her stars’n’stripes bikini and getting fabulous with white colleague Sunshine (Sarah French) for an American bicentenary magazine covershoot. This overcooked 1976-set slasher flick tries to bake in progressive political comment from the start, but it’s clear from the chainsaw-toting maniac in the prologue, and a reference to a then-recently released film, that director Marcel Walz really pledges allegiance to the flag of The Texas Chain Saw Massacre – and that this will be essentially a throwback affair. Makeup artist Sunshine is stepping in front of the camera after first-choice model Raquel (Gigi Gustin), seen ill-advisedly nosing around a set of desert tunnels with her girlfriend in the intro, fails to show.…