Heavens

Everything in the sky follows the game’s clock alone, so co-op players see the same sky.

The sun

The sun circles the disc once a day, 150 km out, and passes under it at night. Night is the disc’s own shadow. Over the year its circle rises and sinks:

Day	Daylight
Midsummer	About 16 hours
Midwinter	About 8 hours

Every few hours the sun erupts. A day later the eruption reaches the disc and lights the aurora.

The moons

Moon	Look	Orbit	Size seen from the middle
Io	Small, silver	4 days	Two thirds of the sun
Ma	Large, amber	16 days	The sun’s own

Io is said eye-oh, and Ma em-ae.

The moons are flat coins with their faces turned down to the land. They have no crescent: a face brightens and dims with the angle the sunlight strikes it. At the midnight that begins the 9th day of every season, both moons stand high and bright together. That is the festival, and the day of the season’s feast.

Eclipses

When a moon passes before the sun, its shadow sweeps across the land. Io is too small to hide the sun and only dims it. Once a year, at noon on the spring festival, Ma hides the sun whole. Its shadow crosses the land in under a minute, and a place under its path stays nearly dark for about 10 seconds.

Night

Night cuts how far armies see to 1.5 km, or 2.5 km under a full moon. Each full moon lights the land in its own colour.

Sight	How often
Shooting star	Every 1 to 3 hours; one in eight is a fireball, seen at any hour
Comet	Every 4 years (256 days), for 12 to 20 days; the first on day 30
Meteor shower	Night of the 11th of autumn, every 4 years
Dust ring shower	First night of winter, every year
Aurora	Nights after the sun erupts, stronger in winter
Nova	About every 2 years, gone in 2 days
Supernova	About every 8 years, fading over 4 days
Magnetar flare	Once or twice a year
Sky waves	8 to 10 nights a year, fading over 10 hours

Four pulsars blink among the stars, each at its own beat. A ring of pale dust circles the disc 160 km out, just past the sun.

Tides

The sea rises and falls with pulls from the sun (0.4 m), Io (0.6 m) and Ma (0.9 m). Each body lifts the sea while it is up and lets it sink while it is under the disc. The sea never moves more than 1.9 m from its level, and the festival’s spring tides run highest. Lakes and rivers have no tide.

The air

The sky is a dome of air the disc’s own size, standing on its rim and 20 km high. Outside it there is only the dark of space.