The document discusses the four basic principles of design: contrast, repetition, alignment, and proximity (CRAP). It provides details on each principle: Contrast involves making elements look different to make some stand out; Repetition creates unity through consistent visual elements; Alignment refers to purposefully placing elements so they are connected; Proximity is used to group related elements together or separate different groups. Mastering these four principles can help designers understand why something may not be working and identify issues quickly.