diff --git a/pipeline/arcade_measure.mjs b/pipeline/arcade_measure.mjs
new file mode 100644
index 0000000..1af68f2
--- /dev/null
+++ b/pipeline/arcade_measure.mjs
@@ -0,0 +1,103 @@
+#!/usr/bin/env node
+// PROCITY Lane E — arcade_measure.mjs  (R39, item 39.4)
+//
+// THE SIZING LAW, MADE RUNNABLE. R38 paid for the law with `paling_fence`: a perfectly good
+// 1,121-tri panel became a REJECTED asset the moment Lane B counted the placement rule (5 runs ×
+// 181 lots = 905 instances = 1.01 M triangles). The law is therefore: an asset's budget is
+// `tris × the instance count the consuming lane's placement rule implies`, and you get that number
+// BEFORE you generate. This script is that number for the arcade, so no later round has to trust a
+// prose figure.
+//
+//     node pipeline/arcade_measure.mjs [seed ...]
+//
+// Everything here is read out of Lane A's own `generatePlan` and Lane B's own constants; nothing
+// is estimated. Constants mirrored from web/js/world/buildings.js are named at the point of use —
+// if they move, this file is the second place to change (the R27 same-literal-in-two-files trap,
+// declared rather than hidden).
+import { generatePlan } from '../web/js/citygen/plan.js';
+
+const AWNING_DEPTH = 2.2, AWNING_Y = 2.95, POST_INSET = 0.2;   // buildings.js:21-22, :643
+const FOOT = 3.5;                                              // ground.js:14
+const seeds = process.argv.slice(2).length ? process.argv.slice(2).map(Number)
+  : [20261990, 7, 123456, 999, 20260101];
+
+const rows = [];
+for (const s of seeds) {
+  const plan = generatePlan(s);
+  const arc = plan.districts.find((d) => d.kind === 'arcade');
+  const nodeById = new Map(plan.streets.nodes.map((n) => [n.id, n]));
+  const aEdges = plan.streets.edges.filter((e) => e.kind === 'arcade');
+  const len = aEdges.reduce((t, e) => {
+    const a = nodeById.get(e.a), b = nodeById.get(e.b);
+    return t + Math.hypot(b.x - a.x, b.z - a.z);
+  }, 0);
+  const width = aEdges[0].width;
+  const aBlocks = plan.blocks.filter((b) => b.district === arc.id);
+  const bIds = new Set(aBlocks.map((b) => b.id));
+  const lots = plan.lots.filter((l) => bIds.has(l.block));
+  const lotIds = new Set(lots.map((l) => l.id));
+  const shops = plan.shops.filter((sh) => lotIds.has(sh.lot));
+  const byType = {};
+  for (const sh of shops) byType[sh.type] = (byType[sh.type] || 0) + 1;
+  const skins = new Set(plan.shops.map((sh) => String(sh.facadeSkin).replace(/\.jpe?g$/, '').replace(/^facade-/, '')));
+  rows.push({
+    seed: s, len: +len.toFixed(2), width, blocks: aBlocks.length, lots: lots.length,
+    shops: shops.length, byType,
+    frontage: [Math.min(...lots.map((l) => l.w)), Math.max(...lots.map((l) => l.w))],
+    meanFrontage: lots.reduce((t, l) => t + l.w, 0) / lots.length,
+    depth: [Math.min(...lots.map((l) => l.d)), Math.max(...lots.map((l) => l.d))],
+    twoStorey: shops.filter((sh) => sh.storeys >= 2).length,
+    townShops: plan.shops.length, townLots: plan.lots.length,
+    distinctSkins: skins.size,
+    unmarked: Math.max(2, Math.min(12, Math.round(plan.shops.length * 0.06))),
+  });
+}
+
+const f = (n, d = 2) => Number(n).toFixed(d);
+console.log('THE ARCADE, MEASURED (synthetic only — plan_osm.js:305 is one unconditional');
+console.log('addDistrict("mainstreet"), so no cache town has an arcade DISTRICT. Real towns do have');
+console.log('1,102 arcade-KIND edges = 39 km of ordinary suburban footpath: key any arcade dressing');
+console.log('on district.kind, never on edge.kind. That is the v9 cut list as a code rule.\n');
+console.log('seed        lane          blocks lots shops 2-storey frontage(m)      depth(m)     town shops  skins  unmarked');
+for (const r of rows) {
+  console.log(`${String(r.seed).padEnd(11)} ${f(r.len)} m × ${r.width} m   ${r.blocks}     ${String(r.lots).padStart(2)}   ${String(r.shops).padStart(2)}    ${String(r.twoStorey).padStart(2)}    `
+    + `${f(r.frontage[0])}–${f(r.frontage[1])} (µ ${f(r.meanFrontage)})  ${f(r.depth[0])}–${f(r.depth[1])}   ${String(r.townShops).padStart(4)}       ${r.distinctSkins}     ${r.unmarked}`);
+}
+const sh = rows.map((r) => r.shops);
+console.log(`\nSHOPS PER ARCADE over ${rows.length} seeds: ${Math.min(...sh)}–${Math.max(...sh)}  (charter says 17; seed 20261990 = ${rows[0].shops})`);
+console.log('types seen:', JSON.stringify(rows.reduce((a, r) => { for (const [k, v] of Object.entries(r.byType)) a[k] = (a[k] || 0) + v; return a; }, {})));
+
+// ── the geometry the dressing has to live inside ────────────────────────────────────────────────
+const half = rows[0].width / 2;
+console.log('\nTHE LANE, from Lane B\'s own constants:');
+console.log(`  lot faces stand at ±${f(half)} m from the centreline ⇒ WALKABLE ${f(half * 2)} m between shopfronts`);
+console.log(`  buildings.js gives every use:'shop' lot an awning ${AWNING_DEPTH} m deep at y=${AWNING_Y} m, so the two`);
+console.log(`  slabs reach to ±${f(half - AWNING_DEPTH)} m ⇒ THE ARCADE IS ALREADY ROOFED EXCEPT A ${f((half - AWNING_DEPTH) * 2)} m SLOT`);
+console.log(`  down the centreline. Ceiling height is ${AWNING_Y} m — a hanging sign must clear EYE 1.62 and sit under it.`);
+console.log(`  ⚠ THE POSTS ARE IN THE WRONG PLACE. buildings.js:643 plants the two awning posts at`);
+console.log(`  d/2 + ${AWNING_DEPTH} − ${POST_INSET} = ${f(AWNING_DEPTH - POST_INSET)} m out from the lot face, i.e. ±${f(half - (AWNING_DEPTH - POST_INSET))} m from the centreline —`);
+console.log(`  TWO ROWS OF POSTS ${f((half - (AWNING_DEPTH - POST_INSET)) * 2)} m APART DOWN THE MIDDLE OF A ${f(half * 2)} m LANE. They carry no collider`);
+console.log('  (colliders.push(lotCollider(lot)) only), so the lane is walkable and the charter\'s 4.99 m');
+console.log('  stands — but visually the arcade is a colonnade planted in its own doorway. AWNING_DEPTH');
+console.log('  2.2 was sized for a 3.5 m FOOT band, not a 2.5 m half-lane. → Lane B ask, see LANE_E_NOTES.');
+console.log(`  ground.js pave: the arcade branch emits ONE footpath quad ${f(rows[0].len)} × ${f(rows[0].width + FOOT * 2)} m`);
+console.log(`  = ${f(rows[0].len * (rows[0].width + FOOT * 2), 0)} m² — the single biggest surface in the district, and it wears footSkin today.`);
+
+// ── the budget line every arcade asset has to answer ────────────────────────────────────────────
+console.log('\nINSTANCE COUNTS THE CONSUMING LANE IMPLIES (the number to generate against):');
+const n = rows[0].shops;
+const rows2 = [
+  ['hanging blade sign', 'one per arcade shop', n, 'synthetic only'],
+  ['shuttered facade skin', 'the dead tenant(s)', 1, '1–2 of the arcade\'s shops'],
+  ['arcade floor skin', 'one merged ground class', 1, 'one town-wide mesh'],
+  ['arcade roof/ceiling', 'one quad over the lane', 1, '1–2 chunks hold arcade lots'],
+  ['A-frame board', 'arcade ~4 + v9 unmarked cue', 4 + rows[0].unmarked, `≤${4 + rows[0].unmarked}/town (unmarked = clamp(round(shops×0.06),2,12))`],
+  ['key-cutter sign', 'the arcade\'s one trade sign', 1, 'landmark, not a repeat'],
+];
+for (const [what, rule, cnt, note] of rows2) {
+  console.log(`  ${what.padEnd(22)} ${String(cnt).padStart(2)} × ${rule.padEnd(28)} ${note}`);
+}
+console.log('\nA GLB CANNOT RIDE boxMats (BoxGeometry + one shared untextured shell material), so each');
+console.log('distinct GLB geometry is +1 draw. Ride it as ONE TOWN-WIDE InstancedMesh (magpie.js\'s');
+console.log('pattern, count 0 or 1..N) and it is +1 total; make it a per-chunk furniture class and it is');
+console.log('+1 × up to 25 live chunks, which at 8 draws of margin is a breach, not a cost.');
diff --git a/pipeline/build_manifest.py b/pipeline/build_manifest.py
index 2857d5c..e5f5924 100644
--- a/pipeline/build_manifest.py
+++ b/pipeline/build_manifest.py
@@ -104,6 +104,15 @@ FACADE_TYPES = {
     "market-fruit": ["stall"], "market-edge": ["stall"],
     "warehouse-roller": ["pawn", "general"], "warehouse-tin": ["pawn", "general"],
     "arcade-entry": ["general"],           # arcade portal, not a shop — Lane B places by key
+    # ── R39 / v9 39.4 — the arcade's dead tenant. PLACED BY KEY, never drawn from a type pool:
+    # `shuttered` is deliberately absent from registry.js's SHOP_TYPES[*].facades, so no shop can
+    # roll it, and a shop that is OPEN must never wear a shutter. It is shot at 768x595 (1.29:1),
+    # the measured arcade lot aspect (mean frontage 3.87-4.05 m against FACADE_H 3.0), not the
+    # main-street pool's 1.78:1 — skins.js paints every facade into a SQUARE atlas slot, so a
+    # 1.78:1 source on a 1.29:1 quad is a 38% horizontal stretch. Costs +0 draws, +0 tris and one
+    # of the 14 FREE facade-atlas slots (the synthetic uses 22 of 36; skins.js:facadeAtlasUV warns
+    # and REUSES a slot past 36 — that is the real budget for a facade skin, not bytes).
+    "shuttered": ["general"],
     # residential fronts for use:'house' lots (incl. the milkbar corner-shop's street)
     "res-terrace": ["house"], "res-weatherboard": ["house"],
     "res-fibro": ["house"], "res-brickveneer": ["house"],
@@ -126,6 +135,19 @@ GROUND_USE = {
     # without a vocabulary change.
     "grass-dry": "yard", "grass-temperate": "yard", "coastal-sand": "yard",
     "bitumen-reddust": "road",
+    # ── R39 / v9 39.4 — THE ARCADE'S TWO SURFACES. These two `use` values name slots that DO NOT
+    # EXIST YET, and unlike gravel→"verge" / reddust→"outback" (R38: selected by nothing, by
+    # accident) that is DELIBERATE and costed. The arcade cannot ride an existing slot: `footpath`
+    # is one town-wide merged mesh, so re-using it would lay terrazzo over every footpath in town.
+    # Each therefore needs its own class, and the price is stated:
+    #   arcade-floor   +1 draw TOWN-WIDE (ground.js builds once, not per chunk: a 6th merged mesh),
+    #                  +0 tris — the 42.00 x 12.00 m = 504 m2 lane quad MOVES out of footGeos.
+    #   arcade-ceiling +1 draw in the 1-2 chunks that hold arcade lots, +2 tris (one 42 x 5 m quad).
+    # BOTH are synthetic-only by construction: plan_osm.js:305 is one unconditional
+    # addDistrict('mainstreet'), so no cache town has an arcade DISTRICT. Key on district.kind and
+    # never on edge.kind — the corpus has 1,102 arcade-KIND edges = 39 km of ordinary suburban
+    # footpath (v9 cut list). And both must be classic-gated: ?classic=1 does not move on dressing.
+    "arcade-floor": "arcade-floor", "arcade-roof": "arcade-ceiling",
 }
 # ── curated: interior floor / surface split of the tex-* skins ───────────────────────────
 FLOOR_TEX = ["carpet-swirl", "carpet-mustard", "carpet-greygreen", "lino-check", "lino-cork",
diff --git a/pipeline/gen_skins.py b/pipeline/gen_skins.py
index a185810..5d78096 100644
--- a/pipeline/gen_skins.py
+++ b/pipeline/gen_skins.py
@@ -93,6 +93,42 @@ GROUNDS = {   # slug (→ web/assets/gen/ground-<slug>.jpg) : subject
                         "beach sand",
 }
 
+# ── round-39 (v9 39.4): THE ARCADE'S SKINS ──────────────────────────────────────────────────────
+# The synthetic's arcade is a 42.00 m covered lane, 16-17 shops, 2 blocks, already awning-roofed by
+# accident (buildings.js AWNING_DEPTH 2.2 from each lot face, lane half-width 2.5 ⇒ the two slabs
+# meet 0.6 m apart over the centreline) and dressed as NOTHING. These three are the cheapest three
+# surfaces in it, in ascending draw cost:
+#   facade-shuttered   +0 draws, +0 tris — one of the 14 FREE facade-atlas slots (the synthetic uses
+#                      22 of 36; skins.js:facadeAtlasUV warns and reuses a slot past 36)
+#   ground-arcade-tile +1 draw TOWN-WIDE (a 6th merged ground class; ground.js builds once, not per
+#                      chunk), +0 tris — the lane quad moves out of footGeos into its own class
+#   tex-arcade-roof    +1 draw in the 1-2 chunks that hold arcade lots, +2 tris (one 42x5 m quad)
+# Aspect is not decoration: skins.js paints every facade into a SQUARE 341 px atlas slot, and arcade
+# lots are 3.87 x 3.0 m ⇒ ~1.29:1, not the 1.78:1 the main-street pool is shot at. `facade-shuttered`
+# is generated 4:3 so it lands on an arcade lot almost undistorted (1024x768 -> square -> 1.29:1 quad
+# ≈ 1.03 net). Recorded, not retro-fitted to the other 48.
+CEILING = ("Straight-up overhead photograph of {v}, camera pointing vertically at the ceiling, "
+           "completely flat-on with no perspective, evenly lit with no glare, no objects hanging "
+           "down, a uniform repeating surface texture filling the entire frame edge to edge")
+SHUT = ("Straight-on photograph of a CLOSED and vacant small Australian shop front, {v}, no glass, "
+        "no people, no text or lettering anywhere, overcast daylight, flat front elevation filling "
+        "the entire frame edge to edge, nothing else visible")
+ARCADE = {
+    # slug : (template, subject, width, height, style)
+    "ground-arcade-tile": (GROUND,
+        "the tiled floor of a 1970s Australian shopping arcade, small terrazzo and mosaic floor "
+        "tiles in beige, terracotta and cream laid in a simple repeating geometric pattern, "
+        "grouted joints, polished and worn smooth by foot traffic", 1024, 1024, "GROUND_STYLE"),
+    "tex-arcade-roof": (CEILING,
+        "the underside of a covered shopping arcade roof, cream pressed-metal ceiling panels in a "
+        "repeating square pattern between painted steel beams, with panels of ribbed wired glass "
+        "letting grey daylight through", 1024, 1024, "GROUND_STYLE"),
+    "facade-shuttered": (SHUT,
+        "a corrugated steel roller shutter pulled all the way down over the whole shopfront, faded "
+        "cream paint with rust streaks and scuff marks along the bottom, a blank empty signboard "
+        "above it, a scuffed tiled stall-riser at the base", 1024, 768, None),
+}
+
 PROMPTS = {
     # ── shop-type facades that the registry is thin on ──────────────────────────────────
     **{f"facade-{k}": FACADE.format(v=v) for k, v in {
@@ -222,6 +258,24 @@ def harvest():
 if __name__ == "__main__":
     if "--harvest" in sys.argv:
         harvest(); sys.exit(0)
+    if "--arcade" in sys.argv:             # round-39 arcade kit (local only) — see ARCADE above
+        todo = {s: v for s, v in ARCADE.items() if not have(s)}
+        print(f"{len(todo)} arcade skins (MODELBEAST flux2-klein-4b, local·free)")
+        if "--dry-run" in sys.argv:
+            for s in sorted(todo):
+                print(f"  {s}  {todo[s][2]}x{todo[s][3]}")
+            sys.exit(0)
+        if not local_available():
+            print(f"ERROR: MODELBEAST flux_local missing ({FLUX_RUN})."); sys.exit(2)
+        for i, (slug, (tpl, subj, w, h, sty)) in enumerate(sorted(todo.items()), 1):
+            try:
+                fn = gen_local(slug, tpl.format(v=subj), w=w, h=h, seed=39,
+                               style=GROUND_STYLE if sty == "GROUND_STYLE" else None)
+                print(f"[{i}/{len(todo)}] {slug} {w}x{h} ({os.path.getsize(fn)//1024}KB)")
+            except Exception as e:
+                print(f"[{i}/{len(todo)}] {slug} FAILED: {str(e)[:90]}")
+        print("done. Review .genraw/, then --harvest → web/assets/gen/.")
+        sys.exit(0)
     if "--grounds" in sys.argv:            # round-38 ground palette (square tile, local only)
         todo = {f"ground-{s}": GROUND.format(v=v) for s, v in GROUNDS.items()
                 if not have(f"ground-{s}")}
diff --git a/pipeline/meshgod_batch_r39.json b/pipeline/meshgod_batch_r39.json
new file mode 100644
index 0000000..60352b7
--- /dev/null
+++ b/pipeline/meshgod_batch_r39.json
@@ -0,0 +1,29 @@
+{
+  "_comment": "ROUND 39 (v9 39.4) THE ARCADE'S KIT for pipeline/gen_props.py --batch. The synthetic town's arcade is a 42.00 m covered lane, ONE edge of kind 'arcade' at width 5, 2 blocks, 16-17 shops (measured over 5 seeds: 17 @ 20261990, 16 @ 7/123456/999, 17 @ 20260101), mean frontage 3.87-4.05 m, depth 5.1-8.0 m. Path: flux_local -> bg_remove_local -> trellis2_mlx -> normalize.py -> bake_lowpoly.py. $0, on-device, no cloud key. GENERATE NOW, WIRE LATER (R39 brief): nothing here is on a lane's critical path this round.",
+  "_sizing_law": "R38's law, applied BEFORE generating: budget = tris x the instance count the placement rule implies, and can it ride an existing merged list? Measured counts from web/js/citygen/plan.js via pipeline/arcade_measure.mjs. blade-sign: 1 per arcade shop = 17, synthetic only. aframe-board: ~4 in the arcade PLUS v9 Layer 4's unmarked-shop cue at clamp(round(shops*0.06),2,12) = up to 12/town => size for <=16. keycutter-sign: 1. A GLB cannot ride boxMats (BoxGeometry, one shared untextured shell material), so each of these is +1 TOWN-WIDE InstancedMesh draw against the 8-draw margin - one per geometry, not one per chunk. State the draw before wiring.",
+  "_thin_structure_guard": "R38 proved thin structures are NOT a TRELLIS class (hills_hoist wire -> thousands of disconnected fragments; a voxel remesh coarse enough for 600 tris erases the pole). So every prompt here is deliberately CHUNKY: the blade sign is a boxy perspex light-box on a stub, not a plate on a wrought-iron arm; the key sign is a thick solid cut-out slab, not a wire silhouette. The bracket arms are Lane B's boxMats primitives at +0 draws.",
+  "_no_baked_text": "House law since v1: the game overlays the name, the asset never bakes it. Every sign face here is BLANK.",
+  "assets": [
+    {
+      "name": "aframe-board",
+      "prompt": "a two-sided A-frame sandwich board sign standing open on a footpath, two thick hinged plywood panels leaning against each other, painted bright chipped yellow around a plain blank white sign face on each panel, a short chain between the legs, a cheap discount-shop pavement sign, whole object from feet to top hinge",
+      "height_m": 0.9,
+      "tris": 400,
+      "for": "39.4 the arcade's two-dollar shop AND v9 Layer 4's unmarked-shop cue (<=16 instances/town)"
+    },
+    {
+      "name": "blade-sign",
+      "prompt": "a boxy rectangular illuminated perspex shop sign that projects out from a wall, a thick white light-box with a bright red plastic frame and completely blank empty faces, mounted on a short square stub at the back, a 1970s Australian arcade projecting sign, whole object",
+      "height_m": 0.55,
+      "tris": 400,
+      "for": "39.4 the arcade's hanging shopfront signage (17 instances) - SEE the +0-draw alternative in LANE_E_NOTES before wiring this"
+    },
+    {
+      "name": "keycutter-sign",
+      "prompt": "a large thick flat shop sign cut out in the shape of an old-fashioned door key, a solid chunky slab silhouette of a key with a round scalloped bow and a simple square-toothed bit, painted worn brass gold with a dark outline, a key cutter's trade sign, whole object, no lettering",
+      "height_m": 0.6,
+      "tris": 500,
+      "for": "39.4 the arcade's one landmark trade sign (1 instance) - lowest value per draw in the kit, see the ranking"
+    }
+  ]
+}
diff --git a/pipeline/seamless_tile.py b/pipeline/seamless_tile.py
new file mode 100644
index 0000000..270e488
--- /dev/null
+++ b/pipeline/seamless_tile.py
@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+"""PROCITY Lane E — seamless_tile.py  (R39)
+
+Make a REGULAR-PATTERN skin tile without a seam, by cropping it to a whole number of its own
+periods instead of blurring the joint.
+
+Why this exists: every ground skin in `web/assets/gen/` tiles through `RepeatWrapping` with the tile
+scale baked into the mesh UVs (`ground.js` TILE = 5 m). Grass and bitumen hide the joint because
+they have no structure. A TILED FLOOR does not — the arcade's 42 x 12 m lane is 504 m2, the single
+biggest surface in the district, and a terrazzo grid whose lines jump at every repeat reads as a
+mistake rather than as a floor. The usual fix (offset + feather) is wrong for a grid: it smears the
+grout lines. The right fix is arithmetic — find the pattern's pitch and cut on it.
+
+    PY=~/Documents/MODELBEAST/venvs/mflux/bin/python
+    $PY pipeline/seamless_tile.py IN.png OUT.png [--check OUT_3x3.png]
+
+Pitch is found by autocorrelating the mean-absolute column/row gradient (a grout line is a gradient
+spike; the spacing of the spikes IS the pitch), searching 24..W/3 px. Prints the residual seam error
+so the result is falsifiable: the mean |difference| between the left and right edge columns before
+and after. If the image has no periodic structure the correlation is flat and the script says so and
+copies the input through rather than cropping something arbitrary.
+"""
+import sys
+import numpy as np
+from PIL import Image
+
+
+def pitch(sig, lo=24):
+    """Dominant period of a 1-D signal, by normalised autocorrelation."""
+    x = sig - sig.mean()
+    n = len(x)
+    hi = max(lo + 1, n // 3)
+    ac = np.correlate(x, x, mode="full")[n - 1:]
+    ac = ac / (ac[0] or 1)
+    band = ac[lo:hi]
+    if band.max() < 0.12:                     # no periodic structure worth cutting on
+        return None, float(band.max())
+    return int(lo + band.argmax()), float(band.max())
+
+
+def edge_err(a, axis):
+    """Mean |difference| across the wrap seam, 0-255."""
+    if axis == 1:
+        return float(np.abs(a[:, 0].astype(np.float32) - a[:, -1].astype(np.float32)).mean())
+    return float(np.abs(a[0].astype(np.float32) - a[-1].astype(np.float32)).mean())
+
+
+def main():
+    src, dst = sys.argv[1], sys.argv[2]
+    im = Image.open(src).convert("RGB")
+    a = np.asarray(im).astype(np.float32)
+    g = a.mean(axis=2)
+    gx = np.abs(np.diff(g, axis=1)).mean(axis=0)      # column gradient profile -> vertical lines
+    gy = np.abs(np.diff(g, axis=0)).mean(axis=1)      # row gradient profile   -> horizontal lines
+    px, cx = pitch(gx)
+    py, cy = pitch(gy)
+    before = (edge_err(np.asarray(im), 1), edge_err(np.asarray(im), 0))
+    print(f"in {im.size}  pitch x={px} (r={cx:.2f})  y={py} (r={cy:.2f})  seam before x={before[0]:.1f} y={before[1]:.1f}")
+    if px is None and py is None:
+        print("no periodic structure found — passing through unchanged")
+        im.save(dst)
+        return
+
+    # PER-AXIS, AND ONLY IF IT ACTUALLY HELPS. Measured on the R39 arcade pair: a diffusion-drawn
+    # tiled floor is NOT periodic enough to cut on (autocorrelation peaked at r=0.26/0.30 and the
+    # "period" it found was not the grout pitch), and cropping to it made the seam WORSE — 27.9→31.9
+    # across x. So the crop is a proposal that has to beat the measurement it is trying to improve,
+    # per axis, or it is discarded. A tool that can only make a number worse is worse than no tool.
+    def try_axis(p, axis, full):
+        if not p or full // p < 2:
+            return full, None
+        return (full // p) * p, None
+    W, _ = try_axis(px, 1, im.width)
+    H, _ = try_axis(py, 0, im.height)
+    cand = im.crop(((im.width - W) // 2, (im.height - H) // 2,
+                    (im.width - W) // 2 + W, (im.height - H) // 2 + H))
+    c = np.asarray(cand)
+    trial = (edge_err(c, 1), edge_err(c, 0))
+    keep_x, keep_y = trial[0] < before[0], trial[1] < before[1]
+    if not keep_x:
+        W = im.width
+    if not keep_y:
+        H = im.height
+    x0, y0 = (im.width - W) // 2, (im.height - H) // 2
+    out = im.crop((x0, y0, x0 + W, y0 + H))
+    b = np.asarray(out)
+    after = (edge_err(b, 1), edge_err(b, 0))
+    print(f"out {out.size}  keep x={keep_x} y={keep_y}  seam after x={after[0]:.1f} y={after[1]:.1f}"
+          + ("" if (keep_x or keep_y) else "   ← NO IMPROVEMENT AVAILABLE, passed through"))
+    out.save(dst)
+    if "--check" in sys.argv:
+        chk = sys.argv[sys.argv.index("--check") + 1]
+        t = Image.new("RGB", (out.width * 3, out.height * 3))
+        for i in range(3):
+            for j in range(3):
+                t.paste(out, (i * out.width, j * out.height))
+        t.resize((out.width, out.height), Image.LANCZOS).save(chk)
+        print(f"3x3 tiling check -> {chk}")
+
+
+main()
diff --git a/web/assets/gen/facade-shuttered.jpg b/web/assets/gen/facade-shuttered.jpg
new file mode 100644
index 0000000..fa8eb43
Binary files /dev/null and b/web/assets/gen/facade-shuttered.jpg differ
diff --git a/web/assets/gen/ground-arcade-floor.jpg b/web/assets/gen/ground-arcade-floor.jpg
new file mode 100644
index 0000000..38faa2b
Binary files /dev/null and b/web/assets/gen/ground-arcade-floor.jpg differ
diff --git a/web/assets/gen/ground-arcade-roof.jpg b/web/assets/gen/ground-arcade-roof.jpg
new file mode 100644
index 0000000..4e7247e
Binary files /dev/null and b/web/assets/gen/ground-arcade-roof.jpg differ
diff --git a/web/assets/manifest.json b/web/assets/manifest.json
index 1685959..64369d1 100644
--- a/web/assets/manifest.json
+++ b/web/assets/manifest.json
@@ -304,6 +304,13 @@
         ],
         "signboard": "blank"
       },
+      "shuttered": {
+        "file": "gen/facade-shuttered.jpg",
+        "types": [
+          "general"
+        ],
+        "signboard": "blank"
+      },
       "res-terrace": {
         "file": "gen/facade-res-terrace.jpg",
         "types": [
@@ -394,6 +401,14 @@
       }
     ],
     "ground": {
+      "arcade-floor": {
+        "file": "gen/ground-arcade-floor.jpg",
+        "use": "arcade-floor"
+      },
+      "arcade-roof": {
+        "file": "gen/ground-arcade-roof.jpg",
+        "use": "arcade-ceiling"
+      },
       "asphalt1": {
         "file": "gen/ground-asphalt1.jpg",
         "use": "road"