Psychedelic visual culture exploded in San Francisco and London in the mid-1960s, inseparable from the counterculture, LSD, and rock music. Concert posters by Wes Wilson, Victor Moscoso, and Bonnie MacLean defined the look: hand-lettered type that melted into itself, vibrating complementary colors, Art Nouveau curves pushed to the point of illegibility. The goal was to create images that mirrored altered states of perception.
The style waned in the 1970s but never disappeared. It resurfaced in rave culture flyers of the early 1990s, in the liquid light shows of electronica, and in the maximalist corners of web design where CSS gradients and animation made screen-based psychedelia possible for the first time without images.
On the modern web, psychedelic design uses conic and radial gradients to simulate the kaleidoscopic color fields that poster artists once achieved with split-fountain printing. Hue-rotate animation replaces the optical vibration of complementary colors. The aesthetic remains deliberately overwhelming — a rejection of the clean, scannable, conversion-optimized page in favor of pure visual experience.