Magical gene / fields and regions

Accretion

One long boundary running the length of the horse, dividing it into a pale field and a coloured one. This locus decides whether there is one at all and what colour it is; Accretion Field decides which half of the horse it takes.

What it can come out as

Outcome	Carrying
Top Accretion	`Acr/Acr` · `Acr/Acc` · `Acr/n` and a copy of `Atp` at Accretion Field
Coloured Top Accretion	`Acc/Acc` and a copy of `Atp` at Accretion Field
Bottom Accretion	`Acr/Acr` · `Acr/Acc` · `Acr/n`
Coloured Bottom Accretion	`Acc/Acc`
Wild type	`Acc/n` · `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 694 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
`Acr/Acr`	Bottom Accretion	0.006% — 1 in 16,667
`Acr/Acc`	Bottom Accretion	0.012% — 1 in 8,333
`Acr/n`	Bottom Accretion	0.114% — 1 in 877
`Acc/Acc`	Coloured Bottom Accretion	0.012% — 1 in 8,333
`n/n`	Wild type	99.856%

Its gene carrot

The file

common/src/main/resources/horsegenetics/genes/accretion.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.accretion`
Phase	magical — it adds signed colour in phase 3, after the pigment has resolved
Priority	270 — where it sits in the one `(priority, key)` paint order
Alleles	`Acr` · `Acc` · `n`
Varies per horse	4 values drawn once off the expressing allele copy, so a foal that inherits the copy inherits the look
Built from	AXIS, NOISE, PARTS, TOWARD

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.

Top Accretion

The pale field is the topline instead - crest, dorsal neck, withers, back, loin, croup and the top of the hip, a fifth to two-fifths of the horse, bounded by a line at half to two-thirds of the body depth measured down from the spine. The legs are excluded entirely. About half of these horses take the mane as well. Which half of the horse goes pale is not decided here: it is read off Accretion Field, and one copy of its topline allele is enough.

the dorsal field — AXIS × NOISE, painted with TOWARD
the mane, on about half of them — PARTS × NOISE, painted with TOWARD

Coloured Top Accretion

The topline field in a colour the line carries rather than pale. Fully recessive at this locus: it takes two copies, and a single copy beside the pale allele shows pale. It never gives blue eyes, whatever the pale form does.

the dorsal field, in colour — AXIS × NOISE, painted with TOWARD
the mane, on about half of them, in colour — PARTS × NOISE, painted with TOWARD

Bottom Accretion

The pale field is the underside: a quarter to nearly half the horse, bounded by a single line running nose-to-tail at a third to a half of the local body depth measured up from the belly, rising a little over the shoulder and rather more over the flank. The boundary undulates gently and has no edge at all - it is a gradient a hand's span or two wide. All four legs are included the whole way to the hoof with no separate boundary of their own, and about three horses in five also take a cap on the muzzle.

the ventral field — AXIS × NOISE, painted with TOWARD
the legs, the whole way down — PARTS, painted with TOWARD
the muzzle cap — PARTS, painted with TOWARD

Coloured Bottom Accretion

The underside field in a colour the line carries rather than pale. Fully recessive at this locus: it takes two copies, and a single copy beside the pale allele shows pale. It never gives blue eyes, whatever the pale form does.

the ventral field, in colour — AXIS × NOISE, painted with TOWARD
the legs, the whole way down, in colour — PARTS, painted with TOWARD
the muzzle cap, in colour — PARTS, painted with TOWARD

Wild type

No accretion.

Paints nothing.