Mitosis

Mitosis splits one cell into two daughters and destroys the parent. A cell divides only once its nucleus is full, and that is not enough on its own: a cell carrying a behaviour gene still has to decide to divide, or the player has to make it. Each daughter’s genome is rolled separately from the parent’s, so neither daughter is guaranteed to match the parent or the other daughter.

Division requirements

The gate is the nucleus, and vacuole storage does not count toward it.

Vacuoles feed the nucleus continuously, with diminishing returns as the vacuole count rises, and mitochondria divert their output into it once cytosol is near full. Both feeds run faster the fuller the cell’s stores already are. The nucleus reaches twice its resting area at threshold, so its size reads how close the cell is.

The threshold is per cell. It rises with:

• genome complexity
• senescence
• the number of neighbours touching the cell
• a heritable per-cell multiplier

A full nucleus is still not a division. A cell carrying a behaviour gene is re-tested every tick on whether its replicate output clears its own divide threshold, a heritable value between 0.1 and 0.7 that drifts as the genome mutates. A cell whose replicate output sits at zero can stay ready indefinitely and never divide on its own. Growth Media does not bypass that test: it lowers the bar and adds to the output, and a cell that still fails still waits. A cell that passes does not split at once: the division fires a fixed number of ticks later, the same number at every playback speed.

A cell with no behaviour gene never takes that test. It divides on a separate path, which waits on a ready nucleus, a cytosol buffer above a set fraction of its span, and an unbroken eligibility delay.

Readiness is lost two ways. At or just above its minimum cytosol buffer a nucleus bleeds its accumulation back down by half the threshold each second, emptying a full one in about two seconds, and readiness clears once it falls under the bar. The bar itself also moves: the crowding and senescence penalties only rise, so crowding a ready cell can un-ready it.

Dividing a cell by hand

The fast pulse wins when both conditions hold.

Both are drawn from cell flags, not from ownership. The fast pulse appears on any mitosis-capable nucleus at threshold, contaminants included. A contaminant refuses every player input, so a pulse on one is a readout rather than an offer, and it never shows the slow pulse. Neither pulse is drawn on a plasmodium, or on an amoeba without a lysosome.

Double-clicking multiplies the vacuole-to-nucleus transfer rate by a large factor for a bounded window, and the division fires the moment the nucleus crosses. If the reserve was short, the feed stops and the cell is still one, now with emptier vacuoles.

A single click on a nucleus that is not ready starts that same feed rather than doing nothing. On a cell carrying the amoeba gene neither click lands at all.

The Trigger Mitosis key, bound to F by default, acts on the current selection and on nothing else:

• It divides every selected cell whose nucleus is ready.
• It buys a trophin dose for each of the rest.
• Only the dose is charged against the dish balance.
• The batch stops at the first refused charge.
• A body plan that cannot spend the dose (a heterokaryon, an archaeon) is skipped rather than billed.

Cytosol cost

A click, a double click and the Trigger Mitosis key all begin the division directly and charge no cytosol.

An autonomous division does charge, and charges before the split: a per-daughter cytosol cost, doubled, scaled by the cell’s own heritable mitosis-cost multiplier. Dragging an organelle out until its tether fully strains fires the same path and pays the same.

A cell with no behaviour gene pays more. Its charge is scaled again by its cytosol-capacity gene, so a small cell pays proportionally far more, and the branch that fires on its own eligibility timer adds a biomass tax per organelle on top.

If paying would push the cell under its minimum buffer, it does not divide.

The cytosol the cell holds at the split is halved, and each daughter gets one half. If that half is at or below the death threshold, the parent is killed on the spot and no daughters appear.

Inheritance

Every vacuole and mitochondrion is duplicated during the pinch so both poles get a copy, and each daughter’s count is then trimmed to what its own genome codes for. What a duplicated vacuole was holding is split evenly between the copies. The rest of the organelles are partitioned across the two poles. Each daughter gets a freshly reset nucleus and spawns at 82% of the radius it will settle at.

Both genomes are rolled separately from the parent’s genome union, each sampled against the substrate at its own pole, so daughters splitting into different terrain drift in different directions.

A division that came from a nucleus click, from the rapid feed, or from the Trigger Mitosis key forces one randomly chosen gene in the first daughter to mutate. Every other route forces nothing, and can hand both daughters the parent’s genome unchanged. Contaminant lineages run one extra mutation pass per division on top.

Replication by body plan

Abort conditions

Mitosis is staged across many frames and the parent can die inside that window. It aborts:

• if the cell’s real cytosol sits in the death zone for a sustained stretch
• if it takes sustained lethal environmental drain on low reserves
• if its net metabolic flux stays negative that long
• if the sequence overruns its time budget

An abort kills the parent, unless the division was starved by the engine’s own pacing budget before either daughter existed.