Colour of the outer arms and colour of the inner disc, blended in OKLab. The core burns toward white and newly formed stars take on a warmer shade of the second colour.

Colour behind the galaxy.

glow adds light for dark backgrounds, ink stipples coloured stars for light ones. auto picks from the background brightness.

Number of stars, from 2,000 to 250,000.

Size of the stars in pixels. Stars nearer the camera draw slightly larger.

Share of brighter, larger stars scattered through the disc, from 0 to 1.

Number of spiral arms, from 1 to 8.

How tightly the arms wind. Higher values give tighter, more numerous turns.

How strongly stars crowd into the arms, from 0 (a smooth disc) to 1.

Darkness of the dust lanes that run along the inner edge of each arm, from 0 to 1.

Brightness of the central bulge, from 0 to 3.

Radius of the central bulge, as a fraction of the galaxy's radius.

Radius of an empty hole at the centre, from 0 to 0.6. Combine with more arms for a ringed galaxy.

Thickness of the disc. Stars scatter above and below it, most of all near the centre.

Viewing angle in degrees, from 0 (face-on) to 85 (nearly edge-on).

Rotation of the whole galaxy on screen, in degrees.

Size of the galaxy relative to the frame.

Horizontal position of the centre, from 0 (left) to 1 (right).

Vertical position of the centre, from 0 (top) to 1 (bottom).

Rotation speed. Inner stars orbit faster than outer ones, so the arms stay put while stars stream through them. Negative values turn it the other way.

How much individual stars shimmer, from 0 to 1.

How much the far side of the disc dims, from 0 (flat) to 1.

Soft haze around bright regions, from 0 to 3.

Overall exposure.

Respond to the pointer.

Sweeping the pointer across the disc gathers nearby stars into a faint tidal filament. The galaxy's rotation winds it into a new trailing arc, which then relaxes back into the disc.

Clicking sends a soft ring of compressed stars outward from the click point, like the density wave of a ring galaxy. Newly formed stars light up as it passes.

How strongly a sweep gathers stars, from 0 to 3.

Strength of the click ring, from 0 to 3.

How much the rotation quickens and the disc brightens while the pointer is over it, from 0 to 2.

Freeze the rotation. Reduced-motion users always get a still frame.

Resolution scale from 0.25 to 1. Lower values are cheaper on large screens.

ripple() sends a ring outward from the centre, for example when a form is submitted.

Content placed over the background.

Classes for the root element. It fills its parent, with a 240px minimum height.

Inline styles for the root element.