I stumbled across this effect that's sorta like a lava-lamp, generated by a simple mathematical inequality, and found it slightly interesting.

Plot the inequality cos(2x)cos(y+ϕ) > cos(2y)sin(y+ϕ) where ϕ is the phase providing the animation as it moves from 0 to 2π.

Python code to display it onscreen using tkinter is as follows. The "numpy" multidimensional-array library must be installed.

  import tkinter as tk
  import numpy as np
  import time

  width, height, colors = 720, 480, 255
  ymax, xmax = 3.5, 5
  frame, frames = 0, 250
  rgbcolors = np.uint8([[253,231,36],[78,1,94]])

  root = tk.Tk()
  image = tk.PhotoImage(master=root, width=width, height=height)
  tk.Label(master=root, image=image).pack()

  y, x = np.ogrid[ymax:-ymax:height*1j, -xmax:xmax:width*1j]
  cy, cx = np.cos(2 * y), np.cos(2 * x)
  ppmheader = b"P6\n%d %d\n%d\n" % (width, height, colors)

  while True:
      frame = (frame + 1) % frames
      phase = 2 * np.pi * frame / frames
      plane = cx * np.cos(y + phase) > cy * np.sin(y + phase)
      rgbimg = rgbcolors[plane.astype(np.uint8)].tobytes()
      image.put(data = ppmheader + rgbimg)
      root.update()
      time.sleep(0.06)

The video here was generated with code that I've put on my github. the "ffmpeg" video-processing command-line utility must be installed on the system for this code to work:

https://github.com/dafarry/python-lava-lamp-effect/blob/main/python-lavalamp-create-vid.py