Magical gene / spots and rings

Lantern

A soft line of bioluminescence running the length of the topline from poll to croup, broken here and there where the light fails to carry.

What it can come out as

Outcome	Carrying
Lantern	`La/La` · `La/n`
Wild type	`n/n`

How each one is actually drawn - region by region, and the layers it is built from - is on the coding tab.

Crossing two of them

Finding one

About 1 in 2,500 wild horses is born showing this. That is the whole of the supply: catch one, or make one with the carrot below. Breeds set their own pools and a breed built around this gene will carry it far more often than the wild population does.

Wild pair	Shows as	How often
`La/La`	Lantern	0.002% — 1 in 50,000
`La/n`	Lantern	0.038% — 1 in 2,632
`n/n`	Wild type	99.96%

Its gene carrot

The file

common/src/main/resources/horsegenetics/genes/lantern.json — a data-driven gene, not a Java class. It is listed in the index.json beside it and registered by Genes' class initialiser at startup.

Key	`horsegenetics.lantern`
Phase	magical — it adds signed colour in phase 3, after the pigment has resolved
Priority	303 — where it sits in the one `(priority, key)` paint order
Alleles	`La` · `n`
Varies per horse	5 values drawn once off the expressing allele copy, so a foal that inherits the copy inherits the look
Built from	AXIS, CENTERLINE, NOISE, PARTS, TOWARD, emissive

Why it is built this way

The three layers are one light source now rather than a lit line beside two painted ones. The core carries the gene's dial ('burn'), so one horse's topline smoulders and another's blazes; the bloom and the mane carry flat, dimmer levels. They are flat because the format has no arithmetic - 'a fifth of the core' cannot be written - and a constant under the dial's own floor of 0.35 keeps the core the brightest thing on every horse, which is what the eye reads. The falloff is free: a glow is scaled by its layer's coverage, and the bloom's CENTERLINE already fades over 1.2 units, so the light spills away from the line exactly as far as the paint does.

'burn' does not run to 0. A lantern horse with no light in it is a horse wearing a coloured stripe, which is not what the locus is for; 0.35 is dim enough to read as 'barely lit' beside a 1.0 sibling.

What it paints

Each outcome, described the way the gene file describes it, and then the layers that draw it in the order they are painted. The prose is the part a reader checks a bake against; the list underneath is what the engine actually did.

Lantern

A line of light along the spine, brightest at its core and dissipating into a soft bloom either side. It breaks in places - a lantern horse rarely carries an unbroken line - and the same colour shows faintly through the mane where the line passes under it. One copy is as lit as two: the horse cannot turn it off, and in the dark it is the only part of it you see.

the bloom either side of the line — CENTERLINE × AXIS, painted with TOWARD, and it glows at 22%
the lit core of the line, broken in places — CENTERLINE × AXIS × NOISE, painted with TOWARD, and it glows, by an amount that varies per horse
the light carried a little way into the mane — PARTS × AXIS × NOISE, painted with TOWARD, and it glows at 18%

Wild type

No lantern line.

Paints nothing.