Metabolism M2.8: rock — inert resource the song drops and builders quarry, carry and build with; livelier metabolisms

metabolism/DESIGN.md

@@ -130,6 +130,17 @@ locked with the kick pairs diggers with haulers — and it feeds the
 other, truce and trade versus skirmish and siege. Society is a property of
 the mix, at both scales.
 
+### Rock — the inert resource
+The map also carries **rock**: height per cell, impassable above a threshold.
+The world is born with a deterministic scatter of it; the song is its weather
+— strong low/mid hits drop stone (crushing what they land on), strong high
+hits shatter it, drops rain it, breakdowns weather it away. Food does not
+recharge through rock, so capped ground is barren until opened. Builders
+**quarry** it (rock → carried burden, and the grinding yields soil), **carry**
+it, and **build** with it — walls rise where the colony works. Rock is the
+one thing on the map that is neither food nor life: it shapes where the
+geography can go at all.
+
 ### Law — regime per section
 Section boundaries are found where the 4 Hz feature cloud changes its mind
 (cheap self-similarity, not an FFT of the FFT), classified into
@@ -294,6 +305,9 @@ world behind the `Run` is being rebuilt.*
   the living well timeline. The world's economy is food-limited: colonies
   bloom on wells, starve off bare ground, and must keep moving to keep
   eating.
+- **M2.8 — rock** ✔ built: the inert resource — scattered at birth, dropped
+  and shattered by the song, impassable, quarried by builders into carried
+  burden and soil, walled where the colony works. See EVOLUTION.md.
 - **M3 — lens** the camera travels (track / reveal / establish) and reserves
   cuts for musical punctuation.
 - **M4 — film** mux frames + PCM to video.