It's Such a Beautiful Day (2012)

Of course, as devotees of Hertzfeldt's very particular aesthetic have known all the way back to his career-making Rejected from 2000 (itself one of the most important pieces of American animation in the last couple of decades), the director's use of the most basic, scrawling style is at the very heart of why his films work so well: unlike more polished, detailed, or stylised cartoons, the very simplicity of Hertzfeldt's art, not unlike the studied cleanliness of a comic strip like Peanuts, allows the viewer to read into the images whatever they want, to overlay with their own thoughts and meanings.