Psychedelia

Psychedelia is an early light synthesizer developed by Jeff Minter and published by Llamasoft in 1984

Psychedelia allows a user to generate a light show on the screen grid, using the joystick to send pulses or bursts of coloured squares. There are various preset settings, or the user can manually set the variables controlling the pulses. Patterns can be recorded to memory or tape for later playback.

Unlike Minter's later synthesizers such as Neon, Psychedelia does not use audio as a factor, only using a joystick's input. It is, however, intended to be played in accompaniment to music.

Minter had been considering "dynamic interactive pattern generators" but hadn't coded any previously. An idea for an algorithm came to him, in which patterns would be seeded along a path, which would then expand and change shape and colour over time. He coded it in 6502 assembler language, fitting into about 1 kilobyte. Running the code for the first time had a profound effect on Minter: "It just felt wonderfully new, and somehow primal... it was like the patterns and mandalas that have fascinated humans for millennia, but come to life, under your control..."

Source: https://en.wikipedia.org/wiki/Psychedelia_(light_synthesizer)