Tarkovsky is rather infamous for adapting sci fi novels in the most backwards and counterproductive ways for no good reason. Stalker is technically an adaptation of an action adventure novel called Roadside Picnic - it is basically a story about a thug getting hired to guide a scavenging trip with a bunch of nutjobs and then shit hits the fan. everyone is a piece of shit trying to screw each other. So naturally the movie transforms this story about scum screwing each other into a Bressonian parable about a lot of existential things spiced with “this is deep” monologues for extra eyerolls. It is basically an extended trolling of Michelangelo Antonioni’s latter day work that featured very abstract plotting and functional characterization and lots of stylized set piece shots filled with negative space.