Opossum

What it can come out as

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 595 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.

Its gene carrot

The file

common/src/main/resources/horsegenetics/genes/opossum.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.

Why it is built this way

The rear edge is DITHERED rather than faded (owner's call), and the difference is worth stating because the format makes it easy to get wrong. Coverage scales an op's strength, so an AXIS ramp multiplied by a SPECKLE gives you *faded dots* - every dot present, each one weaker - which reads as a gradient with texture in it rather than as roan running out. Dots that get rarer is a density change, and density is a SPECKLE parameter that no mask can drive. So the falloff is three bands with hard edges and falling densities (0.82, 0.42, 0.16), which is the format's way of writing a density gradient. The band edges are separate knobs kept strictly below 'extent' so no band can invert its own from/to - a reversed pair is smoothstep's degenerate hard step (gap 106), and it would put a solid block where the fringe should be.

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.

Opossum

A restricted grey, and restricted to the front of the horse. White hair comes in over the brow and forehead and can carry back across the face, down the neck, over the chest and the point of the shoulder and down the front legs - how far is settled once and does not move afterwards. It stops at the shoulder: the barrel, the flank, the hindquarter and the hind legs are never involved. Where it reaches the muzzle the skin there goes soft pink whether or not a white marking is present. Every edge is roaned and jagged - heavy sabino, not a cut line - and it affects the mane wherever it touches. The skin around the eyes stays dark. It sits under all white markings, and a bald face or a big blaze simply overrides it. One copy looks exactly like two.

1. grey from the forehead backward — AXIS × SPECKLE, painted with TOWARD
2. the roan thinning out behind it — AXIS × SPECKLE, painted with TOWARD
3. and the last few flecks further back still — AXIS × SPECKLE, painted with TOWARD
4. the mane where the grey touches it — AXIS × SPECKLE, painted with TOWARD
5. a pink muzzle where it gets that far — PARTS × AXIS, painted with TOWARD

Coloured Opossum

The same marking in a colour the line carries rather than in white. Fully recessive: it takes two copies, and a single copy beside a white allele shows white. It never gives blue eyes, whatever the white form does.

1. grey from the forehead backward, in colour — AXIS × SPECKLE, painted with TOWARD
2. the roan thinning out behind it — AXIS × SPECKLE, painted with TOWARD
3. and the last few flecks further back still — AXIS × SPECKLE, painted with TOWARD
4. the mane where the grey touches it, in colour — AXIS × SPECKLE, painted with TOWARD
5. a pink muzzle where it gets that far, in colour — PARTS × AXIS, painted with TOWARD

Wild type

No greying.

Paints nothing.