DAY0.0
MOONS0 / 2
IN WINDOW0/3
STRAIN0%
Empty ledger. Set the first moon.
ORRERY
The sea went out through the broken sluice and took the low ward with it. Gravity is the only lever left: set moons in orbit, let the tide build over weeks, and commit the waterline at the hour when every basin in the city reads between its sill and its crown.
Reading the basins…
The old tide tables are gone. The sills in the ledger were cut from one configuration that ever worked.
The tide waits.
Every moon is where you left it. The water will not move while the ledger is shut.
Five numbers and a clock.
- RADIUS
- How far the moon sits, in planet radii. Near moons raise a huge tide and a short period; far moons are a slow, weak hand.
- TILT
- How far the orbit leans out of the plane. A tilted moon climbs over the poles, so it lifts high-latitude basins at a different hour.
- ECCENTRICITY
- How lopsided the orbit is. A lopsided moon gives a far bigger bulge at periapsis than at apogee, which narrows the hour you can commit.
- BULK
- Mass. It sets both the height of the bulge and how fast the basin refills.
- EPOCH
- Where the new moon stands the moment you set it loose. This is the dial that lines two tides up.
Overlapping bulges simply add. Two moons in the same part of the sky pile their tides on top of each other; two moons a quarter turn apart cancel. The envelope drawn on the planet is the sum, magnified 2.2× so you can see it, and it matches the cross-section panel exactly.
Orbits may not cross: the ledger trims eccentricity to keep a clear hull. Two periods within 2% of a low-order ratio — 2:1, 3:2, co-orbital — build strain, and full strain shears the sky.
Commit only when every basin sits between its sill and its crown at the same instant. The day runs out on its own, and the ledger is judged where it stands.