Close out the twenty: what the gates taught

Three lessons worth more than the scenes: a slow axis has to move a large
low-frequency area or the camera's own drift beats it, whole-frame luminance on
the kick is the strobe the flash gate exists for and it arrives by accident, and
a style trait expressed only as grain measures as no style at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flow-state/LIBRARY-20.md

@@ -65,3 +65,44 @@ before the batch commit.
 | 18 | Halftone Misprint | camera, style | CMY halftone screens, misregistered | nothing else in the library draws dots |
 | 19 | Droste Feedback | camera, style | recursive zoom-and-rotate video feedback around a small motif | Time Smear translates; this scales, so the image eats itself |
 | 20 | Analog Wow | camera, style | tape warp: horizontal wobble, chroma bleed, dropout streaks | Scan Tear and Block Mosh are quantised and blocky; this is continuous and wet |
+
+---
+
+## What landed
+
+All twenty, in six commits, each batch gated before it went in. The library is
+at **62 scenes**: flow, organic, geometric and glitch at ten each, structural and
+minimal at eleven. `space` went from 20 scenes to 28 and `shape` from 21 to 28,
+which was the point — those are the traits that decide whether a track has
+anything to cast.
+
+Three things came out of the build that are worth keeping:
+
+**A slow axis needs a large, low-frequency area, not a detailed one.** Phase 11
+compares ten-second averages, and the camera's own drift moves that average by
+0.01-0.02 on any high-contrast image. An axis that changes line count, drop
+density or tier count loses to it; one that changes a wake's width, a colony's
+extent, a tide level or a deck's height beats it. Seven of the twenty declare an
+axis. Six do not, and each of those files records the candidates measured and
+what they scored — Turing Bloom, Voronoi Shatter, Droste Feedback and Analog Wow
+because a feedback or re-cutting scene's own history moves the average further
+than any parameter can, Contour Map and Balance Stack because the frame is too
+empty for anything in it to out-move a slow pan.
+
+**Two ways to strobe a whole frame, both found by the flash gate.** Driving block
+heights off the low end made every tower in Isometric Blocks grow together — a
+frame-wide luminance cycle on the kick, 4/s. A hard recursion cutoff in
+Apollonian Gasket popped a whole generation of discs in and out as the fold
+crossed it. Local terms and a faded cutoff fixed both.
+
+**Style expressed only as grain is not style.** Six of the twenty first shipped
+with a style response the render gate measured at 11-24 out of 255 — the Side
+Quest 1 complaint, reproduced from scratch. Putting the track's line weight and
+edge softness into the actual subject (the dot, the ring, the seam, the course,
+the band boundary) took them to 86-255.
+
+One check changed: Phase 4's transition control is the sum of the two adjacent
+shots' motion rather than the larger of them. See the commit; the short version
+is that a dissolve has both stacks live and a nonlinear blend of two moving
+stacks moves more than either alone, so the old control was reading its own
+denominator once the library had calm scenes in it.