Vortice Lux: A companion piece to Vortice Umbra.

Concentric, slightly-eccentric ellipses rotate, producing phasing patterns. The ellipses are rendered with drop-shadows, with the light slowly varying over time. Vortice Lux features a light background over which patterns of light and shadow interplay.

Features:

Spacing: Wider spacing produces bolder patterns and emphasises the light and dark spaces. All sizes are equally likely.

Eccentricity: This affects the shape. An eccentricity close to one produces a subtle effect, whilst lower eccentricities emphasise the changes in the spiral.

Rotation: There are three speeds; a relatively-rapid speed, a steady, almost-default speed, and a slower, more contemplative version. The default speed is most likely.

Highlights: The drop-shadow effect is more likely to be light, producing a brighter edge to each set of ellipses. A dark-shadowed version is also available, with a probability of around a quarter.

Inversion: The default mode is a lightly-hued background.