Download Pinwheel by Troy Zerr (11k zip), then run the program and watch the spirals without blinking. When you look away, your field of vision is distorted in flowing waves.
This image (50% full size) was created with my own program, Illusionarium, which can be downloaded as a zip file of 217k by clicking either the link here or the image. It requires a minimum screen resolution of 1024×768.
Figures are created by selecting from a series of pre-set shapes and placing them on an isometric grid. Images can then be saved.
Currently at v2.0, March 2001.
V2.0 NOW HAS ALL THE SHAPES, AND A DRAWING AREA AS LARGE AS POSSIBLE BASED ON THE SCREEN RESOLUTION.