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Document GP-DOC-06: Genetics

Breeding & Inheritance

The legal firewall, stated first. A cross A × B is a deterministic function. Its outcome (the child's full genome and its eight preview stats) is computable and shown in full before any payment. The Cross-Sim station previews any pair, free and unlimited, over your specimens, other players', or live marketplace listings. There is no randomness in a paid operation, and nothing random is ever sold. Random Mendelian segregation (drawing which allele is passed) is prohibited: it would put chance inside a purchase (a direct gambling vector) and contradict "you see the result before you pay". A creature is a game mechanic, never a placement.

Deterministic does not mean shallow. A single cross is solved; a breeding program is not. Depth lives in multi-generational planning toward a target that is conditional on the biome, in the meta rotation (you raise a stable of specialists, not one champion), and in the inbreeding constraint below.

Inheritance rules

For each locus of the child (exact engine code, diversifyBias = 0 in v0):

  • Quantitative loci (co-dominant): child = round_mix(exprA, exprB), the rounded mean of the two parents' expressed values. The child locus is stored homozygous on that value: since a quantitative locus only ever expresses its mean, homozygosity is lossless.
  • LMB (dominance 4 > 3 > 2 > 6): each parent transmits its most recessive allele. So LMB=6 (hexapod) appears in a child only when both parents carry the 6 → hexapods stay rare.
  • FUT (dominance claw > pad > hoof > web): same recessive-gamete rule → webbed feet appear only when both parents carry web → terrestrial webbed specialists stay rare.

The child stores the full diploid genotype, expressed and carried, on-chain, so the pedigree is public and the preview reveals nothing hidden (see The Genome). Rarity is emergent from these rules, not decreed.

Inbreeding depression: the anti-clone mechanism

"Geno pool" is literally the genetic diversity of a population; low diversity means reduced fitness, and the engine implements exactly that:

F = kinship(parentA, parentB)              // common ancestors over PEDIGREE_DEPTH generations
stat_child *= (1 - INBREEDING_PENALTY * F)

PEDIGREE_DEPTH     = 5
INBREEDING_PENALTY = 0.35

F is the coefficient of relationship computed from the on-chain pedigree, bounded to 5 generations. The penalty is a pure function of (stats, F, PENALTY), with no RNG, so it is already folded into the free preview. The effect: crossing close relatives degrades the child, so a min-maxer cannot clone a perfect lineage. A closed line plateaus (a single inbred lineage must cap below the population's 90th percentile). To keep improving, a breeder must outcross with other players' lines, which keeps the marketplace liquid.

Population control

Population is the on-chain count of cages sold; released spawns mint nothing. Two attributes bound production, written on-chain:

Litters:   5 max, then permanent sterility
Cooldown:  6h → 12h → 24h → 48h → 96h   (rising per litter)

Sterility is a demographic valve (anti-inflation of creatures), not a spending engine: measurement showed that capping litters does not slow the race to the optimum, because a champion's offspring are as good as the champion.

Mutations: catalysts, obtained by playing only

Traits outside the base range, and the v1+ reserved genes, are unlocked only by catalysts (HELIX residues). Each catalyst has a deterministic, documented effect (e.g. forcing a carried LMB=6 to express in the child), and the Cross-Sim folds the chosen catalyst into the preview, so the result stays known before payment. Catalysts are won only, from race drops by placement and from expeditions: soulbound in v0, never sold, never in the shop. The randomness is gated by play, not payment.

The economics of the anti-clone

Breeding is a fixed USDC price, independent of the outcome, previewed in full first:

Cross:            4.90 USDC
With a catalyst:  +1.50 USDC (handling; effect is known in advance)

The anti-convergence lives in the economy, not in an engine coefficient. INBREEDING_PENALTY sets the ceiling of a closed line; market friction sets the slope: outcrossing costs (buying outside lines routes commission back through royalties, see Marketplace Registry), and the rising cooldown paces attempts. Without that friction a min-maxer would reach the optimum in two generations; with it, six or more.

Cooldown reduction is deliberately not for sale: it would be a demographic valve disguised as a convenience and a hidden advantage. When both parents are on cooldown, the free Scheduled Cross queues the (already locked) preview to mint when the cooldown clears, at no extra cost.

Related: the Genome it operates on, the Marketplace Registry that carries pedigree and race record, and the Race Rewards that grant catalysts by placement.