Aurora

What it does

Each of the three bands follows a wandering height across the screen with a soft glow around it, and its colour sways between a and b along its length. The bands live in the top half of the screen and are pinned to it; they do not follow the camera.

amount scales brightness and opacity together, so tweening it up from 0 brings the aurora on slowly, and speed sets how fast the curtains drift and sway. Below and between the bands the layer is transparent, so whatever sits under it shows through.

Features

• Three drifting curtains — each at its own height, pace and glow.
• Two colours — blended along each curtain; green and violet by default.
• One brightness dial — amount scales light and opacity together, down to invisible at 0.
• Speed — how fast the curtains move.
• Transparent below — it stacks over a sky or a sunset and under stars.
• Cheap — one pass with three bands of light.

Good for

• Night scenes — a winter level, a frozen north, a calm sky over a camp.
• Magic and arcane moods — recoloured curtains over a wizard's tower or a fantasy title.
• Title screens — faded in by tweening amount from 0.
• Skylines — a glow over a city or a space station's horizon.

Make it yours

Two params and two colours. A polar night is backdrop-sky in navy, the aurora in its default green and violet, and backdrop-stars on top. An arcane sky is pink and gold curtains at a higher speed over a sunset.

A quick look

An aurora that fades in over four seconds, then turns pink:

const aurora = game.backdrop.add('aurora', { amount: 0, speed: 1 }, { a: '#37ff9e', b: '#7a5cff' });
await aurora.tween({ amount: 1 }, { duration: 4 });   // a slow dawn of light
aurora.setColor('b', '#ff5cc8');                      // live

Works with

• backdrops — the runtime; required.
• backdrop-sky or backdrop-sunset — beneath it.
• backdrop-stars — over it.
• backdrop-environments — a complete aurora scene with stars and hills in one pass.

Good to know

• The bands sit in the top half of the screen and do not follow the camera.
• Opacity follows the green in the result, so a pair of colours with no green is faint: give a or b some green.
• Three bands, fixed, and no stars of its own.