Composers like Lizst, Brahms, and Wagner start to incorporate the triangle (the instrument) into their concertos and symphonies, both as a solo instrument and as a complementary piece.

Left- and right-pointed triangles start to appear on tape decks representing "play," "rewind," and "fast forward," the start of a chain that'd lead to their appearance on pretty much anything that can play some kind of media.

Pink Floyd release The Dark Side of the Moon, an album popular among your friends who like to blow smoke rings and do funky tricks after bong hits; its album art features a dope prism.

Joy Division release Unknown Pleasures, a popular T-shirt design that happens to double as a post-punk record. It features a bunch of triangles, and while they're more like raggedy waves than true, strong shapes, they're too popular not to include.

Jay Z, Dame Dash, and Kareem "Biggs" Burke found Roc-A-Fella Records, the label ultimately responsible for dozens of fleshy "diamonds" — they're triangles, come on — thrown into the air by celebrities grasping for an iota of street cred.

After some time out of the spotlight, triangles make a huge comeback in the video for The White Stripes' "Seven Nation Army," a song you can still enjoy if you pretend Jack White had nothing to do with it.

Daft Punk play a headlining set at Coachella inside a big-ass pyramid, one flanked by dozens of smaller (but still exciting) triangles. People love it! It pops up again on the cover of their live LP Alive 2007.

A bunch of witch house bands — remember witch house? No? Me neither, honestly — root their aesthetics in triangles, which we can probably chalk up to their connection to the occult and a collective lack of creativity.

Kesha's video for "Die Young" inspires a torrent of Illuminati conspiracy theories with its onslaught of triangles and triangle-adjacent shapes.

Katy Perry releases a new album called Prism, and while it's free of triangle imagery on a track-by-track basis, her ensuing Prismatic World Tour is just as dependent on triangles as your average bridge or wind-resistant skyscraper.