pH

pH is how acidic or alkaline the ground under a cell is, one of the two conditions engraved into the substrate field and read out on the familiar 0-14 scale, with 7 neutral. Every cell carries a pH tolerance gene that sets the pH it prefers and the safe range either side of it. Outside that range the cell leaks cytosol at a rate that rises the further out it stands.

pH never kills outright. There is no lethal threshold anywhere on the scale, unlike temperature: a cell dies of pH only when the leak empties it, and that death is reported as acidified where the ground was acid and alkalized where it was alkaline.

Cytosol drain

Inside the band the ramp charges nothing. Outside it, drain rises with the square of how far outside, reaching its ceiling 2.8 pH points past the edge at width 1.0. The ramp itself is scaled by the width multiplier. Whatever it charges is then scaled by the cell’s cytosol capacity and by its membrane permeability, so the same bad ground drains a large leaky cell harder than a small tight one.

A width above 1.0 charges a residual: how far above 1.0, times an authored rate, held as a floor under the pH damage rather than added to it. The floor is scaled by how far the ground sits from the optimum as a fraction of the band, so it is nothing at the optimum and full at the band edge. A width below 1.0 pays nothing extra and buys nothing except a smaller target.

The stress badge on the inspect readout fires further out than the band edge, where the drain reaches a fixed threshold, so ordinary field noise just past a razor-thin band raises nothing.

Tolerance band

Two numbers on the pH tolerance gene set the band.

The band reaches about 1.1 pH points either side of a neutral optimum, narrows the further the optimum sits from neutral, and is floored at 0.7 points so a full specialist still survives the pH spread inside one generated zone. The width multiplier scales what survives that floor. A lineage drifting toward an extreme therefore gets a narrower band for the same width setting.

The gene is losable. A cell that loses it behaves as a neutral generalist at width 1.0 and still takes drain at the extremes.

Optimum drift

The optimum moves on a division where the pH tolerance gene is picked to mutate, a per-gene roll at a rate authored per dish and multiplied by any mutagen the culture is under. The daughter’s optimum then takes one step along the axis, weighted toward whichever side of neutral the local ground is on. The step is not aimed at the ground’s value: a cell on mildly alkaline ground is pushed further alkaline even if its optimum has already passed the local pH. The weighting is never a gate, and a step against the gradient stays possible at every strength, only smaller.

• Within roughly 0.7 pH points of neutral. The weighting is skipped and the step is symmetric.
• Past that. The weighting scales with distance from neutral.
• At pH 1.4 and 12.6. Full strength, where a counter-gradient step is cut to an eighth and a with-gradient step is multiplied by 1.6.

Extreme ground also raises how large and how often mutations land, so a dish taken to an extreme drifts a lineage several times faster than a mildly off-neutral one.

Directed mutation

Double-clicking a cell’s nucleus applies a paid dose. It charges trophin and reads the ground around that cell. On the pH axis it forces the width or the optimum, never both:

• If the pH spread around the cell is wider than the strain’s own band, no single optimum covers that ground, and the dose forces the width axis wider on the next division.
• Otherwise, if the pH under the cell is more than about 0.7 points off neutral, it forces the optimum instead.

Either way the forced step closes a fifth to two fifths of the remaining gap: to the local pH for the optimum, to the 2.5 maximum for the width. Four to eight dosed divisions take a neutral strain to an extreme.

A band-carrying mutagen compound overrides the ground entirely. An acid-band compound drives the optimum acid and an alkaline-band one drives it alkaline, wherever the cell is standing, and its tier sets how far, linearly, with tier IV aiming at the rail.

Sources of ground pH

pH spreads by diffusion through the substrate and is not pulled back toward neutral the way temperature is pulled back toward ambient. A patch driven acid stays acid until something else drives it the other way.

Metabolism does not write pH, and nothing fills a pH vacuole. The organelle can still be evolved and still charges its maintenance drain, but it banks nothing and releases nothing, so building one costs a cell and changes no ground.

The field is written by:

• Death. A corpse stamps the cell’s own preference, pulled 80% of the way from neutral toward its optimum, at a strength scaling with how far from neutral it stood and with the energy it died holding. A neutral cell leaves almost nothing.
• An endoplasmic reticulum in secretor mode, driving local pH toward an evolvable set-point, at a strength rising with how many secretors the cell carries.
• Digestive enzymes carrying a pH modifier, which shift the field where the cloud bursts, by the direction and weight that modifier evolved.
• Acid and alkaline compounds, the crystals that emit them, and the environment brush, which blend a patch toward a stated target.

Ecotype

The optimum is quantised into buckets about 1.1 pH points wide, fixed regardless of the cell’s own width multiplier and centred on the starter’s neutral. That bucket joins the cell’s temperature bucket, its transmembrane organelles and its flagellum count in one surface signature. Two strains in the same bucket hash identically and are the same ecotype; a strain that drifts out of it is not, which is what lets a cell accept a corpse fragment from a stranger and raise a targeted antibody. It also separates a player strain from a rival contaminant clade, which is built from the same starter and differs only on these two axes.

Scrap compounds

A scrapped cell pays out compounds named for the band its pH gene sits in, counted in the cell’s own tolerance bands rather than in pH points:

Width therefore changes the answer: a razor-thin specialist and a wide generalist at the same optimum do not scrap the same compound. The band picks the compound’s root word, and a Neutral band gets the bare roster word with no root at all. It does not set the mass paid, and a strain carrying none of the genes the roster points at yields nothing at any optimum.

Ground colour

One eight-stop ramp carries pH from acid to alkaline. The ground is painted with it, the environment lens redraws the dish from it, and the environment bar in the HUD draws the same ramp.

How much of the ramp a dish shows depends on the pH spread its generation was given, which is authored per dish. A dish generated close to neutral never leaves the segment between the two stops flanking neutral, and the rest of the ramp appears only where something has driven the field there.

The lens reads the pH channel alone rather than the tinted ground, and repaints cells from the same ramp by their own optimum, brighter than the ground: a cell whose hue matches the ground beneath it is adapted to where it is standing, and one that clashes is adapted to ground somewhere else. A separate mismatch lens drops the hue and tints every cell by how far its optimum sits from the local field, on the worse of the pH and temperature axes, so adapted cells go dark and only the maladapted ones burn.

With no lens open, a cell body carries a pH tint of its own on a three-stop ramp: crimson for an acid specialist, icy blue-green at neutral, violet for an alkaline one, shifted by the cell’s temperature optimum.