Magical gene / ground and strong white

Beetle Pearl

A hard black barrel scattered with pearls, a pale cap over the poll and a dark fork down the face - a pearl-spotted beetle rather than a spotted horse. A third allele carries the same marking worked in greys instead of white - dark where the pale form is light, and the same number of steps.

What it can come out as

Outcome	Carrying
Beetle Pearl	`Bpw/Bpw` · `Bpw/Bpc` · `Bpw/n` · `Bpw/Bpk`
Beetle Pearl, black	`Bpk/Bpk` · `Bpk/Bpc` · `Bpk/n`
Beetle Pearl, coloured	`Bpc/Bpc`
Wild type	`Bpc/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 1,786 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
`Bpw/Bpw`	Beetle Pearl	0.002% — 1 in 50,000
`Bpw/Bpk`	Beetle Pearl	0.0027% — 1 in 37,495
`Bpw/Bpc`	Beetle Pearl	0.0027% — 1 in 37,495
`Bpw/n`	Beetle Pearl	0.038% — 1 in 2,632
`Bpk/Bpk`	Beetle Pearl, black	0.0027% — 1 in 37,495
`Bpk/Bpc`	Beetle Pearl, black	0.0027% — 1 in 37,495
`Bpk/n`	Beetle Pearl, black	0.0027% — 1 in 37,495
`Bpc/Bpc`	Beetle Pearl, coloured	0.0027% — 1 in 37,495
`n/n`	Wild type	99.944%

Its gene carrot

The file

common/src/main/resources/horsegenetics/genes/beetle_pearl.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.beetle_pearl`
Phase	magical — it adds signed colour in phase 3, after the pigment has resolved
Priority	221 — where it sits in the one `(priority, key)` paint order
Alleles	`Bpw` · `Bpk` · `Bpc` · `n`
Varies per horse	6 values drawn once off the expressing allele copy, so a foal that inherits the copy inherits the look
Built from	AXIS, CENTERLINE, PARTS, SPOTS, TOWARD

Why it is built this way

Imported from the magic-gene intake, 2026-09-08. The ground goes to black before anything else, which is why this reads the same on a chestnut as on a black. The source used perDose coverage to make the heterozygote fainter; that was dropped, because a perDose triple on an expression the first allele does not reach is silently zero (gap 105) and this locus is simple dominant.

The black allele is the white one with the light taken out of it, and it sits one rung under white in the dominance series - so every combination that existed before it keeps the outcome it had, and only the pairs carrying Bpk are new. The re-toning is a mapping rather than a repaint: every achromatic target moves into the dark end of the scale keeping its order and its spacing, and every SATURATED one is left alone, because that colour is the gene rather than its lightness.

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.

Beetle Pearl

The ground goes to black before anything else, so the pearls have something to be pearls against - on a chestnut as much as on a black. The spot field is mirrored, so the two flanks match, which is what separates this from an ordinary appaloosa.

the barrel taken to a hard black — PARTS, painted with TOWARD
pearls scattered over it, mirrored side to side — SPOTS, painted with TOWARD
a pale cap over the poll — AXIS, painted with TOWARD
a dark fork down the face — CENTERLINE, painted with TOWARD
dark ear tips — AXIS, painted with TOWARD

Beetle Pearl, black

The same marking as the white form with the light taken out of it: the same 2 steps, moved to the dark end of the scale.

the barrel taken to a hard black — PARTS, painted with TOWARD
pearls scattered over it, mirrored side to side — SPOTS, painted with TOWARD
a pale cap over the poll — AXIS, painted with TOWARD
a dark fork down the face — CENTERLINE, painted with TOWARD
dark ear tips — AXIS, painted with TOWARD

Beetle Pearl, coloured

The same black ground with the pearls in a colour the line carries. Fully recessive.

the barrel taken to a hard black — PARTS, painted with TOWARD
pearls scattered over it, mirrored side to side — SPOTS, painted with TOWARD
a pale cap over the poll — AXIS, painted with TOWARD
a dark fork down the face — CENTERLINE, painted with TOWARD
dark ear tips — AXIS, painted with TOWARD

Wild type

No pearls.

Paints nothing.