The red isn't dying

Era 9 gives some winter days that still grew a leaf a small red tint at each leaf's own tip, on a clear day only. The obvious reading is autumn's reading: red means a leaf on its way out. It doesn't, here. Autumn's amber (era 2's fall flag) is chlorophyll actually breaking down as a deciduous leaf senesces and prepares to drop — the green pigment that was masking the yellow and orange ones underneath finally gets out of the way. Era 9's leaves never drop, and the red isn't a leftover pigment being unmasked; the plant is actively making it, for a reason that has nothing to do with dying. Hughes, Neufeld & Burkey's 2005 study of Galax urceolata, an evergreen forest-floor plant, lays out the real mechanism: cold weather slows the leaf's photosynthetic machinery down, but a clear winter sky keeps delivering light at the usual rate, so a cold, bright leaf is stuck absorbing more energy than it can use. That surplus is dangerous — it can chew through chlorophyll faster than the leaf can replace it. Anthocyanin, the same red pigment, works here as sunscreen: it sits above the chlorophyll and absorbs the excess light before it does damage. The color fades once the cold spell ends and the leaf's own machinery can keep up again. A living, reversible response, not a step toward shedding anything.

The code keeps that distinction structurally, not just in prose. rules.fall is still only ever true in autumn; a blushing leaf in this room is drawn from the exact same leaf path autumn's amber ones and every other season's green ones are, with a small <circle class="blush-mark"> laid over its own tip afterward, at the same coordinate era 8 already collects for guttation's own drop — see the field note on that room. Two different real phenomena that both end up reading as "the leaf has red on it" would have been an easy thing to collapse into one flag; keeping them apart cost nothing more than gating the new mark on season === "winter" instead of rules.fall.

Where this room is honest about compressing something: a real cold snap builds its blush gradually, over days, and lets it fade the same slow way once it warms. This file has no memory between dates to build a gradient out of — see weather with no yesterday for why that's a promise, not a gap I forgot to close — so a date's blush is one flat fact, decided once: on or off, full tint or none. And not every plant does this at all; Galax urceolata is one real, well-studied example of a real category, not a claim that every evergreen out there is doing exactly this on every cold, clear day. This room draws one stylized version of a real thing, the same honest scale da Vinci's own branching rule already admitted to.