Vitality

One model, every organism

Fish, plants and algae experience the tank through the same interface. Each hour an organism declares what is harming it, what it costs to stay alive, and what is doing it good; one shared module turns those three lists into a condition and a reserve. Species configs decide which resources map to which factors — the arithmetic is identical across lifeforms.

net = Σbenefits − (Σupkeep + Σstressors) × (1 − hardiness)

Term	Is	Scaled by hardiness
Benefits	Income from favourable conditions, in %/h	No
Upkeep	The cost of simply being alive, in %/h	Yes
Stressors	Damage done to the organism, in %/h	Yes
Hardiness	Species tolerance plus a per-individual offset, 0–1	—

Hardiness scales the charged side only. A hardy fish tolerates bad water; it is not more energised by good water.

The two ledgers

Which list a deficit lands in decides which stock it reaches. That split is the whole model.

Ledger	Weighs	A shortfall is paid in
Energy	Benefits against upkeep	Tissue. The organism shrinks and survives
Health	Whatever income the energy ledger left, against stressors	Condition. The organism is intact but damaged

The energy ledger settles first, and a deficit on it never doubles as condition damage. A starving plant loses biomass rather than health, which is the difference between a plant that is small and a plant that is dying.

The surplus bank

Income that is not spent accrues into a saturating reserve, and the reserve buffers damage before condition falls. A well-stocked organism shrugs off a bad hour by burning stores; the same hour flattens one that has nothing banked.

Two claims reach different depths of the same bank, and the ordering is what keeps a poisoned organism from starving itself.

Claim	Seniority	May spend
Upkeep	Senior	The bank to its last unit
Damage	Junior	Only what stands above a reserved depth — a few hours of upkeep, held back as survival rations
Repair and growth	Junior	The same spendable part, above the same floor

Accrual saturates at a cap and overflow beyond it is discarded rather than queued, the way a body absorbs only so much of a vitamin. One reading follows from all of this and is easy to misread: condition 100 with a negative net means burning reserves, not thriving.

Recover, then grow

Nothing in the balance repairs an organism that stores its energy. Repair is a withdrawal from the bank, taken ahead of growth, so a stressed organism pays down its deficit before it makes any progress. An organism with no energy ledger runs the same ladder from the other end — its income heals it on the spot, and only a full condition leaves anything to bank.

Either way the trajectory is the same shape: recover, then grow. There is no middle position where an organism parks, damaged but stable.

Organism	Ledgers	Damage reaches	The bank buys
Fish	Health only — income heals first and banks what a full condition leaves	condition	Breeding, which spends a share of the cap from both parents
Plants	Both — income pays upkeep first, and what neither income nor bank covers is starvation	condition, and tissue for unpaid upkeep	Repair first, then new size, both stopping at the survival floor
Algae	Neither — a bloom has no condition at all, so net folds straight into the bank	mass	Mass, capped per hour and asymptotic toward a ceiling

Deliberate absences

Three things are missing on purpose, and each has been re-proposed before.

Absent	Why
A condition-equilibrium term	Behaviour that reads as “everything dies eventually” is severity constants too harsh at the margin — a real defect, but a number, never a missing mechanism
Husbandry re-tests on outcomes	Outcomes spend the stock. The husbandry is already priced into how the bank filled, so breeding’s one guard is that the female’s net is non-negative this hour, which tests trend rather than conditions
Hardiness on the benefit side	Tolerance is protection from harm, not an appetite for good conditions

Status

Mechanic	Status	Why
The balance	settled	One formula for every organism, with hardiness applied centrally rather than by each caller
The two ledgers	settled	Energy deficits are paid in tissue, environmental stress in condition
The bank and its reserved depth	settled	One definition of the floor, subtracted once, so no claimant can forget it
Recover-then-grow	settled	No middle-parking; the missing equilibrium term is a decision, not a gap
Tolerance-band benefits	scaffolding	A step by its own account — crossing a tolerance edge loses the whole benefit at once and starts damage

Source

src/simulation/systems/ holds the shared model and each organism’s factor builders; src/simulation/plants/, src/simulation/algae/ and src/simulation/livestock/ decide what their surplus is spent on.