// Dungeon map — a real 2D floor plan first, 3D built from it.
//
// Standard roguelike construction, all seeded (no Math.random, no wall-clock):
// rejection-sampled non-overlapping rectangular rooms, Kruskal MST over room
// centres plus loop edges, L-shaped corridors carved between linked rooms.
// The walk route is a closed travelling tour (greedy nearest-room BFS legs,
// returning to the start), smoothed and resampled to even arclength.
//
// Why grid-first: every wall is derived from cell occupancy (a wall run exists
// exactly where open meets solid), so the shell has no holes by construction;
// the camera only ever stands on open cells (route or room watch cells), so
// it can never be inside a wall; and the route is a real walkable path
// (BFS-verified), not a ribbon bent through blockwork.
//
// Contract:
//   dungeonCharacter(summary) -> { indoorBias, murk, sizeMul, dark, slow }
//   genDungeon({ seed, rng, summary }) -> DungeonPlan (pure data, serialisable)
//   pathAt(plan, s) -> { x, yaw }          (world units, wraps)
//   roomAt(plan, s) -> roomId (>=0) | -1    (corridor)
//   zoneAt(plan, s) -> zone name
//   CELL: world units per cell
//
// Song → dungeon mapping (see dungeonCharacter): dark/slow/heavy songs get
// sealed, murky, big-roomed dungeons with no outside views; bright/fast
// songs get airier ruins with forest and wallwalk openings. Same seed +
// same summary is the same dungeon; the seed alone is not.
//
// DungeonPlan:
//   { seed, w, h, grid, rooms, wallRuns, ceilRects, route, items, portal, watch, character, theme }
//   grid: Uint8Array open cells; rooms: [{id,x,y,w,h,cx,cy,zone,indoor}]
//   wallRuns: [{x0,z0,x1,z1,h}] world-space merged runs (axis aligned)
//   ceilRects: [{x0,z0,x1,z1,y}] world-space ceiling slabs (indoor only)
//   route: { pts:[{x,z}], cum:[...], totalLen, roomIds:[], zones:[] }
//   items: { props, torches, puddles, windows, gates, gaps, patrols, ... }
//   portal: {x,z,yaw,roomId} | null; watch: { roomId: {x,z,lookX,lookZ} }
//   character: { indoorBias, sealed, murk, sizeMul, dark, slow } — the mapping above
//   theme: one of THEME_NAMES — the venue's visual identity for this song

import { Rng } from '../../engine/rng.js';
import { smooth01 } from './shared.js';

export const CELL = 2.0;
const FLOOR_Y = -1.15;
const GW = 44;
const GH = 44;
const ROOM_TARGET = 8;
const ROOM_MIN = 5;
const ROOM_MAX = 10;
const ROOM_ATTEMPTS = 500;

const clamp01 = (x) => Math.max(0, Math.min(1, x));

/**
 * Song → dungeon character. Pure f(summary); every field that matters about
 * the track's sound is read here once, so the whole venue derives from one
 * documented mapping instead of scattered heuristics. Calibrated against the
 * measured 17-song bank, not arrangement intent — two measurement quirks
 * shape the design:
 *
 * - Tempo doubling: beatless/broken tracks read ~2x (drone 62→170). bpmF
 *   folds readings above 150 back down; the seal veto below still uses the
 *   unfolded reading, because doubling only ever inflates — 160+ measured
 *   is genuinely fast either way.
 * - Hiss masking: noisy tracks read spectrally bright whatever sits under
 *   the hiss (murk 0.915 ≈ glare 0.912), so darkness alone cannot find
 *   murk's quadrant; flatness + pace + weight can.
 *
 * - indoorBias 0..1: how sealed the dungeon is. Dark + slow songs approach
 *   1 (mostly stone, few openings); blazing masters (centroid ≈ 1) are
 *   cracked open toward ~0.2 regardless of pace.
 * - sealed bool: fully indoor — every room and corridor roofed, no outside
 *   views. Darkest tonal master (dark ≥ 0.5), or hissy slow weight
 *   (flat > 0.55, slow > 0.3, heavy > 0.4, un vetoed). In the bank exactly
 *   dusk + murk seal; fast hiss (grit/plate) stays open and moves.
 * - murk 0..1: gloom the facade applies as dimmer lights + closer, darker
 *   fog. Tonal darkness first, hiss and stillness behind it.
 * - sizeMul 1..1.45: room footprint multiplier. Slow + loud songs get
 *   fewer, bigger masses instead of small rooms.
 */
export function dungeonCharacter(summary = {}) {
    const t = summaryTraits(summary);
    let indoorBias = clamp01(0.3 + t.dark * 0.65 + t.slow * 0.3 + t.still * 0.1);
    if (t.dark < 0.05) indoorBias *= 0.55;
    return {
        indoorBias: t.sealed ? 1 : indoorBias,
        sealed: t.sealed,
        murk: clamp01(t.dark * 0.8 + Math.min(1, (summary?.meanFlatness ?? 0.15) * 1.4) * 0.15 + t.still * 0.15),
        sizeMul: 1 + clamp01(t.slow * 0.55 + t.heavy * 0.45) * 0.45,
        dark: t.dark,
        slow: t.slow,
    };
}

/**
 * Shared audio traits for the venue mapping — one source of truth for
 * dungeonCharacter (layout) and dungeonTheme (identity) so the two can
 * never disagree about what a song sounds like. Pace terms gate on
 * tempoConfidence: doubled detectors report high bpm with low confidence
 * (drone 170 @ 0.24), and trusting those readings raw would call every
 * ambient track fast.
 */
function summaryTraits(summary = {}) {
    const s = summary || {};
    const bpm = s.bpm ?? 120;
    const dark = 1 - Math.min(1, (s.meanCentroid ?? 0.5) * 1.4);
    const bpmF = bpm > 150 ? bpm / 2 : bpm;
    const slow = clamp01((115 - bpmF) / 45);
    const still = clamp01(((s.dynamicRange ?? 0.5) - 0.35) / 0.55);
    const heavy = clamp01(((s.meanLoudness ?? 0.004) - 0.0002) / 0.0018);
    const noisy = (s.meanFlatness ?? 0.15) > 0.55;
    const paceTrust = clamp01(((s.tempoConfidence ?? 0.5) - 0.3) / 0.4);
    const fast = clamp01((bpm - 120) / 60) * paceTrust;
    const bright = clamp01(((s.meanCentroid ?? 0.5) - 0.5) * 2);
    const dyn = clamp01(((s.dynamicRange ?? 0.5) - 0.3) / 0.5);
    return {
        dark, slow, still, heavy, noisy, fast, bright, dyn,
        sealed: dark >= 0.5
            || (noisy && slow > 0.3 && heavy > 0.4 && bpm <= 160),
    };
}

/**
 * The five dungeon themes — the venue's visual identity per song. Each
 * record is pure data (colors as [r,g,b] arrays, pick lists with repetition
 * as weights, density multipliers), so the plan stays serialisable and the
 * facade just builds materials from it:
 * - stoneMul/floorMul: multipliers on the palette-driven stone/floor colors
 * - torch: absolute flame emissive + torch-light color
 * - fogTint: multiplier on the fog color (atmosphere grade per theme)
 * - wood: absolute timber color
 * - propIndoor/propOutdoor: weighted pick lists for room dressing
 * - vegMul: boundary planting density · timberMul: wall-beam budget share
 * - puddleMul: puddle count share
 */
export const THEMES = {
    crypt: {
        stoneMul: [1.0, 1.0, 1.05], floorMul: [1.0, 1.0, 1.05],
        torch: [1.0, 0.55, 0.18], fogTint: [1.0, 0.95, 0.9], wood: [0.21, 0.13, 0.07],
        propIndoor: ['rubble', 'furniture', 'rubble', 'banner', 'stalagmite'],
        propOutdoor: ['trees', 'rubble', 'rampart', 'trees'],
        vegMul: 1.0, timberMul: 1.0, puddleMul: 1.0,
    },
    overgrown: {
        stoneMul: [0.85, 1.05, 0.85], floorMul: [0.85, 1.05, 0.85],
        torch: [0.4, 0.9, 0.6], fogTint: [0.9, 1.0, 0.9], wood: [0.25, 0.18, 0.1],
        propIndoor: ['rubble', 'banner', 'stalagmite', 'rubble', 'bush'],
        propOutdoor: ['trees', 'trees', 'bush', 'boulder', 'trees'],
        vegMul: 1.5, timberMul: 0.7, puddleMul: 1.0,
    },
    ember: {
        stoneMul: [1.05, 0.85, 0.8], floorMul: [1.05, 0.85, 0.8],
        torch: [1.0, 0.3, 0.12], fogTint: [1.0, 0.85, 0.8], wood: [0.12, 0.08, 0.06],
        propIndoor: ['rubble', 'stalagmite', 'stalagmite', 'rubble', 'banner'],
        propOutdoor: ['boulder', 'rubble', 'rampart', 'boulder'],
        vegMul: 0.5, timberMul: 0.6, puddleMul: 0.5,
    },
    flooded: {
        stoneMul: [0.95, 1.0, 1.1], floorMul: [0.9, 1.0, 1.1],
        torch: [0.6, 0.8, 1.0], fogTint: [0.9, 0.95, 1.05], wood: [0.2, 0.16, 0.12],
        propIndoor: ['furniture', 'banner', 'rubble', 'furniture'],
        propOutdoor: ['bush', 'rampart', 'trees', 'bush'],
        vegMul: 0.8, timberMul: 0.8, puddleMul: 2.0,
    },
    windswept: {
        stoneMul: [1.1, 1.05, 0.95], floorMul: [1.1, 1.05, 0.95],
        torch: [1.0, 0.9, 0.75], fogTint: [1.05, 1.0, 0.95], wood: [0.3, 0.22, 0.14],
        propIndoor: ['furniture', 'rubble', 'banner', 'rubble'],
        propOutdoor: ['boulder', 'bush', 'rampart', 'boulder'],
        vegMul: 0.7, timberMul: 0.5, puddleMul: 0.7,
    },
};
export const THEME_NAMES = Object.keys(THEMES);

/**
 * Pick the venue's visual identity for a song. Pure f(summary, seed):
 * audio scores pick the region, a small seeded jitter keeps neighbouring
 * songs from collapsing onto one theme. Calibrated corners:
 * dark+slow → crypt, hissy → overgrown, heavy/fast → ember,
 * bright+dynamic → flooded, bright+fast → windswept.
 *
 * Two honest-measurement rules shape the weights (same findings as
 * dungeonCharacter): pace terms gate on tempoConfidence, so doubled
 * detectors don't read fast; crypt is penalised for blazing masters, so
 * bright ambient opens instead of entombing. Jitter is 0.15 — enough to
 * vary re-rolls of genuinely ambiguous songs, too small to flip a decided
 * race. Calibrated against the measured 17-song bank: crypt×4,
 * overgrown×4, ember×4, flooded×4, windswept×1.
 */
export function dungeonTheme(summary = {}, seed = 1) {
    const t = summaryTraits(summary);
    const s = summary || {};
    // Brightness gate kept separate from darkness: a pale but dynamic
    // ballad is flooded, never windswept; speed alone never floods.
    const bright = clamp01(((s.meanCentroid ?? 0.5) - 0.5) * 2);
    const scores = {
        crypt: t.dark * 0.7 + t.slow * 0.4 + t.still * 0.3 - t.bright * 0.4,
        overgrown: (t.noisy ? 1 : 0) * 0.9 + t.slow * 0.2 + (1 - t.dark) * 0.15 - t.fast * 0.4,
        ember: t.heavy * 0.8 + t.fast * 0.3 + (t.noisy ? 1 : 0) * 0.15,
        flooded: t.bright * 0.7 + t.dyn * 0.3,
        windswept: t.fast * 0.9 + t.bright * 0.45,
    };
    const rng = new Rng((((seed >>> 0) || 1) ^ 0x7e3a9) >>> 0 || 1);
    let best = 'crypt', bestScore = -Infinity;
    for (const name of THEME_NAMES) {
        const s = scores[name] + rng.next() * 0.15;
        if (s > bestScore) { bestScore = s; best = name; }
    }
    return best;
}

const zoneIndoor = (z) => z === 'hall' || z === 'room';

const idx = (w, x, y) => y * w + x;
const inBounds = (w, h, x, y) => x >= 0 && y >= 0 && x < w && y < h;

// ------------------------------------------------------------- union-find
// Kruskal MST over room centres: the cheapest standard way to guarantee every
// room joins one connected graph.

function kruskal(n, edges) {
    const parent = [];
    for (let i = 0; i < n; i++) parent.push(i);
    const find = (a) => (parent[a] === a ? a : (parent[a] = find(parent[a])));
    const mst = [];
    const rest = [];
    for (const e of edges) {
        const ra = find(e.a), rb = find(e.b);
        if (ra !== rb) { parent[ra] = rb; mst.push(e); }
        else rest.push(e);
    }
    return { mst, rest };
}

// ------------------------------------------------------------------- BFS
// 4-neighbour shortest paths on open cells. Deterministic: fixed neighbour
// order, first-found wins, so the same grid always yields the same paths.

const NB = [[1, 0], [-1, 0], [0, 1], [0, -1]];

function bfsPath(open, w, h, sx, sy, tx, ty) {
    if (sx === tx && sy === ty) return [{ x: sx, y: sy }];
    const prev = new Int32Array(w * h).fill(-1);
    const qx = [sx], qy = [sy];
    prev[idx(w, sx, sy)] = idx(w, sx, sy);
    let head = 0;
    while (head < qx.length) {
        const cx = qx[head], cy = qy[head];
        head++;
        if (cx === tx && cy === ty) break;
        for (const [dx, dy] of NB) {
            const nx = cx + dx, ny = cy + dy;
            if (!inBounds(w, h, nx, ny) || !open[idx(w, nx, ny)]) continue;
            if (prev[idx(w, nx, ny)] !== -1) continue;
            prev[idx(w, nx, ny)] = idx(w, cx, cy);
            qx.push(nx); qy.push(ny);
        }
    }
    if (prev[idx(w, tx, ty)] === -1) return null;
    const path = [];
    let c = idx(w, tx, ty);
    while (c !== idx(w, sx, sy)) {
        path.push({ x: c % w, y: Math.floor(c / w) });
        c = prev[c];
    }
    path.push({ x: sx, y: sy });
    path.reverse();
    return path;
}

function bfsDist(open, w, h, sx, sy, tx, ty) {
    const p = bfsPath(open, w, h, sx, sy, tx, ty);
    return p ? p.length : Infinity;
}

// ------------------------------------------------------------------ LOS
// Bresenham cell walk between cell centres: every crossed cell must be open.

function losClear(open, w, h, x0, y0, x1, y1) {
    let dx = Math.abs(x1 - x0), dy = Math.abs(y1 - y0);
    const sx = x0 < x1 ? 1 : -1, sy = y0 < y1 ? 1 : -1;
    let err = dx - dy, x = x0, y = y0;
    for (;;) {
        if (!inBounds(w, h, x, y) || !open[idx(w, x, y)]) return false;
        if (x === x1 && y === y1) return true;
        const e2 = 2 * err;
        if (e2 > -dy) { err -= dy; x += sx; }
        if (e2 < dx) { err += dx; y += sy; }
    }
}

// ------------------------------------------------------------------ plan

export function genDungeon({ seed = 1, rng = null, summary = null } = {}) {
    const r = rng ? rng.fork('dungeon:map') : new Rng((seed >>> 0) || 1).fork('dungeon:map');
    const sd = (seed >>> 0) || 1;
    const character = dungeonCharacter(summary);
    const sizeMul = character.sizeMul;
    // Visual identity for this song: the theme record drives dressing mix
    // and densities below; the facade builds materials from the same record.
    // Seeded off the map seed so the identity never shifts sibling streams.
    const themeName = dungeonTheme(summary, sd);
    const theme = THEMES[themeName] ?? THEMES.crypt;

    // --- rooms: rejection-sampled rects with a 1-cell moat between them, so
    // corridors always have somewhere to go and rooms never share walls.
    // Footprints scale with the song's heft (sizeMul): heavy songs get
    // masses, not cells.
    const rooms = [];
    for (let attempt = 0; attempt < ROOM_ATTEMPTS && rooms.length < ROOM_TARGET; attempt++) {
        const w = Math.max(3, Math.round(r.int(ROOM_MIN, ROOM_MAX) * sizeMul));
        const h = Math.max(3, Math.round(r.int(ROOM_MIN, ROOM_MAX) * sizeMul));
        const x = r.int(1, GW - w - 1);
        const y = r.int(1, GH - h - 1);
        let ok = true;
        for (const o of rooms) {
            if (x < o.x + o.w + 1 && o.x < x + w + 1 && y < o.y + o.h + 1 && o.y < y + h + 1) {
                ok = false; break;
            }
        }
        if (ok) rooms.push({ id: rooms.length, x, y, w, h, cx: x + w / 2, cy: y + h / 2 });
    }
    // Degenerate seed insurance: a map with fewer than 3 rooms is a hallway
    // with extra steps — fall back to three fixed rooms (still seeded zones).
    while (rooms.length < 3) {
        const i = rooms.length;
        rooms.push({ id: i, x: 4 + i * 12, y: 20, w: 6, h: 6, cx: 7 + i * 12, cy: 23 });
    }

    const open = new Uint8Array(GW * GH);
    const roomId = new Int16Array(GW * GH).fill(-1);
    const carve = (x, y, id) => {
        if (!inBounds(GW, GH, x, y)) return;
        open[idx(GW, x, y)] = 1;
        if (id >= 0) roomId[idx(GW, x, y)] = id;
    };
    for (const rm of rooms) {
        for (let y = rm.y; y < rm.y + rm.h; y++) {
            for (let x = rm.x; x < rm.x + rm.w; x++) carve(x, y, rm.id);
        }
    }

    // --- links: MST (Kruskal, weight = centre distance + small seeded jitter
    // so parallel runs vary) plus up to 2 loop edges — loops give the tour
    // alternate ways round, and doorways the camera never takes.
    const edges = [];
    for (let i = 0; i < rooms.length; i++) {
        for (let j = i + 1; j < rooms.length; j++) {
            const a = rooms[i], b = rooms[j];
            edges.push({ a: i, b: j, w: Math.hypot(a.cx - b.cx, a.cy - b.cy) });
        }
    }
    edges.sort((p, q) => p.w - q.w);
    const { mst, rest } = kruskal(rooms.length, edges);
    const links = mst.slice();
    const rLoops = new Rng((sd ^ 0x10ee) >>> 0 || 1);
    const shuffledRest = rest.slice();
    for (let i = shuffledRest.length - 1; i > 0; i--) {
        const j = rLoops.int(0, i);
        [shuffledRest[i], shuffledRest[j]] = [shuffledRest[j], shuffledRest[i]];
    }
    for (const e of shuffledRest.slice(0, 2)) links.push(e);

    // --- corridors: L-shaped 1-cell carves between random cells of the two
    // rooms (order seeded). Recorded as rects for exact ceiling cover.
    const rCorr = new Rng((sd ^ 0xc091) >>> 0 || 1);
    const corrRects = [];
    const carveCorr = (x, y) => carve(x, y, -1);
    for (const e of links) {
        const A = rooms[e.a], B = rooms[e.b];
        const ax = rCorr.int(A.x, A.x + A.w - 1), ay = rCorr.int(A.y, A.y + A.h - 1);
        const bx = rCorr.int(B.x, B.x + B.w - 1), by = rCorr.int(B.y, B.y + B.h - 1);
        const horizFirst = rCorr.bool();
        const x0 = Math.min(ax, bx), x1 = Math.max(ax, bx);
        const y0 = Math.min(ay, by), y1 = Math.max(ay, by);
        if (horizFirst) {
            for (let x = x0; x <= x1; x++) carveCorr(x, ay);
            for (let y = y0; y <= y1; y++) carveCorr(bx, y);
            corrRects.push({ x: x0, y: ay, w: x1 - x0 + 1, h: 1, link: e });
            corrRects.push({ x: bx, y: y0, w: 1, h: y1 - y0 + 1, link: e });
        } else {
            for (let y = y0; y <= y1; y++) carveCorr(ax, y);
            for (let x = x0; x <= x1; x++) carveCorr(x, by);
            corrRects.push({ x: ax, y: y0, w: 1, h: y1 - y0 + 1, link: e });
            corrRects.push({ x: x0, y: by, w: x1 - x0 + 1, h: 1, link: e });
        }
    }

    // --- zones: per-room draw against the song's indoorBias. A sealed
    // character closes every room; otherwise indoor rooms split hall/room
    // and the rest open to forest/wallwalk. With 4+ rooms and bias < 1, one
    // room is forced each way so mixed maps always have both stone and sky.
    const rZones = new Rng((sd ^ 0x20e5) >>> 0 || 1);
    const order = rooms.slice();
    for (let i = order.length - 1; i > 0; i--) {
        const j = rZones.int(0, i);
        [order[i], order[j]] = [order[j], order[i]];
    }
    const indoorPool = ['hall', 'room'];
    const outdoorPool = ['forest', 'wallwalk'];
    let sealAll = character.sealed === true;
    order.forEach((rm, i) => {
        let zone;
        if (sealAll || rZones.next() < character.indoorBias) {
            zone = indoorPool[i % indoorPool.length];
        } else {
            zone = outdoorPool[i % outdoorPool.length];
        }
        rm.zone = zone;
        rm.indoor = zoneIndoor(zone);
    });
    if (!sealAll && rooms.length >= 4 && !rooms.some((rm) => !rm.indoor)) {
        const pick = order[rZones.int(0, order.length - 1)];
        pick.zone = outdoorPool[rZones.int(0, outdoorPool.length - 1)];
        pick.indoor = false;
    }
    if (!sealAll && rooms.length >= 4 && !rooms.some((rm) => rm.indoor)) {
        const pick = order[rZones.int(0, order.length - 1)];
        pick.zone = indoorPool[rZones.int(0, indoorPool.length - 1)];
        pick.indoor = true;
    }
    const zoneOf = new Array(GW * GH).fill('hall');
    const indoorOf = new Uint8Array(GW * GH);
    for (const rm of rooms) {
        for (let y = rm.y; y < rm.y + rm.h; y++) {
            for (let x = rm.x; x < rm.x + rm.w; x++) {
                zoneOf[idx(GW, x, y)] = rm.zone;
                indoorOf[idx(GW, x, y)] = rm.indoor ? 1 : 0;
            }
        }
    }
    for (const cr of corrRects) {
        const A = rooms[cr.link.a], B = rooms[cr.link.b];
        const indoor = (A.indoor && B.indoor) ? 1 : 0;
        const zone = indoor ? 'hall' : (A.indoor ? B.zone : A.zone);
        const x1 = cr.x + cr.w - 1, y1 = cr.y + cr.h - 1;
        for (let y = cr.y; y <= y1; y++) {
            for (let x = cr.x; x <= x1; x++) {
                if (!inBounds(GW, GH, x, y)) continue;
                if (roomId[idx(GW, x, y)] === -1) {
                    zoneOf[idx(GW, x, y)] = zone;
                    indoorOf[idx(GW, x, y)] = indoor;
                }
            }
        }
        cr.indoor = indoor;
        cr.zone = zone;
    }

    // --- route: closed travelling tour — start at room 0, repeatedly walk to
    // the nearest unvisited room (BFS distance), then leg home. Closed by
    // construction; every leg BFS-verified walkable.
    const roomCenterCell = (rm) => ({
        x: Math.max(rm.x, Math.min(rm.x + rm.w - 1, Math.round(rm.cx))),
        y: Math.max(rm.y, Math.min(rm.y + rm.h - 1, Math.round(rm.cy))),
    });
    const routeCells = [];
    {
        const start = roomCenterCell(rooms[0]);
        let cur = start;
        routeCells.push({ ...cur });
        const unvisited = new Set(rooms.map((rm) => rm.id));
        unvisited.delete(rooms[0].id);
        while (unvisited.size) {
            let best = null, bestD = Infinity;
            for (const id of unvisited) {
                const c = roomCenterCell(rooms[id]);
                const d = bfsDist(open, GW, GH, cur.x, cur.y, c.x, c.y);
                if (d < bestD) { bestD = d; best = { id, c }; }
            }
            const leg = bfsPath(open, GW, GH, cur.x, cur.y, best.c.x, best.c.y) || [cur];
            for (let k = 1; k < leg.length; k++) routeCells.push(leg[k]);
            cur = best.c;
            unvisited.delete(best.id);
        }
        const home = bfsPath(open, GW, GH, cur.x, cur.y, start.x, start.y) || [];
        for (let k = 1; k < home.length; k++) routeCells.push(home[k]);
    }

    // --- smooth: closed Chaikin ×2 keeps corners inside the carved cells
    // (cuts stay near the polyline; corridors are a full cell wide), then
    // even 0.5-unit resampling with per-sample room/zone tags.
    const toWorld = (cx, cy) => ({
        x: (cx - GW / 2 + 0.5) * CELL,
        z: (cy - GH / 2 + 0.5) * CELL,
    });
    let poly = routeCells.map((c) => toWorld(c.x, c.y));
    for (let it = 0; it < 2; it++) {
        const out = [];
        for (let i = 0; i < poly.length; i++) {
            const p = poly[i], q = poly[(i + 1) % poly.length];
            out.push(
                { x: p.x * 0.75 + q.x * 0.25, z: p.z * 0.75 + q.z * 0.25 },
                { x: p.x * 0.25 + q.x * 0.75, z: p.z * 0.25 + q.z * 0.75 },
            );
        }
        poly = out;
    }
    const pts = [];
    {
        // Even resample: walk the closed polyline in 0.5-unit steps.
        const segLens = [];
        let total = 0;
        for (let i = 0; i < poly.length; i++) {
            const p = poly[i], q = poly[(i + 1) % poly.length];
            const l = Math.hypot(q.x - p.x, q.z - p.z);
            segLens.push(l);
            total += l;
        }
        const STEP = 0.5;
        const n = Math.max(8, Math.round(total / STEP));
        let si = 0, acc = 0;
        for (let k = 0; k < n; k++) {
            const target = (k / n) * total;
            while (acc + segLens[si] < target && si < poly.length - 1) {
                acc += segLens[si];
                si++;
            }
            const p = poly[si], q = poly[(si + 1) % poly.length];
            const f = segLens[si] > 1e-9 ? (target - acc) / segLens[si] : 0;
            pts.push({
                x: p.x + (q.x - p.x) * f,
                z: p.z + (q.z - p.z) * f,
            });
        }
    }
    const cum = [0];
    for (let i = 1; i <= pts.length; i++) {
        const p = pts[i - 1], q = pts[i % pts.length];
        cum.push(cum[i - 1] + Math.hypot(q.x - p.x, q.z - p.z));
    }
    const totalLen = cum[pts.length];
    // Per-sample tags from the containing cell.
    const cellOfPt = (p) => ({
        x: Math.floor(p.x / CELL + GW / 2),
        z: Math.floor(p.z / CELL + GH / 2),
    });
    const sampleRoom = pts.map((p) => {
        const c = cellOfPt(p);
        return inBounds(GW, GH, c.x, c.z) ? roomId[idx(GW, c.x, c.z)] : -1;
    });
    const sampleZone = pts.map((p) => {
        const c = cellOfPt(p);
        return inBounds(GW, GH, c.x, c.z) ? zoneOf[idx(GW, c.x, c.z)] : 'hall';
    });

    // --- walls: one run everywhere INDOOR open meets solid, merged along
    // each axis. No holes possible: every indoor open edge is either
    // open-neighboured or walled. Wall tops match the ceiling slabs exactly
    // (per-zone heights — see ceilRects below), so walls always meet roofs.
    // Outdoor edges grow vegetation instead of half-walls: the outside stays
    // outside, lined with planting rather than masonry.
    const wallRuns = [];
    const vegCells = new Map();
    const noteVeg = (x, y, zone) => {
        if (!inBounds(GW, GH, x, y) || open[idx(GW, x, y)]) return;
        const k = idx(GW, x, y);
        if (!vegCells.has(k)) vegCells.set(k, { x, y, zone });
    };
    {
        // Wall height follows the ceiling over the cell: 'room' zones stand
        // 4.2, halls and indoor corridors 3.2.
        const wallH = (x, y) => (zoneOf[idx(GW, x, y)] === 'room' ? 4.2 : 3.2);
        const hEdges = []; // {z, x0, x1, h}
        const vEdges = []; // {x, z0, z1, h}
        for (let y = 0; y < GH; y++) {
            for (let x = 0; x < GW; x++) {
                if (!open[idx(GW, x, y)]) continue;
                const w0 = toWorld(x, y);
                if (!indoorOf[idx(GW, x, y)]) {
                    // Outside: plant the solid neighbours, wall nothing.
                    const z = zoneOf[idx(GW, x, y)];
                    noteVeg(x, y - 1, z); noteVeg(x, y + 1, z);
                    noteVeg(x - 1, y, z); noteVeg(x + 1, y, z);
                    continue;
                }
                const h = wallH(x, y);
                if (!inBounds(GW, GH, x, y - 1) || !open[idx(GW, x, y - 1)]) {
                    hEdges.push({ z: w0.z - CELL / 2, x0: w0.x - CELL / 2, x1: w0.x + CELL / 2, h });
                }
                if (!inBounds(GW, GH, x, y + 1) || !open[idx(GW, x, y + 1)]) {
                    hEdges.push({ z: w0.z + CELL / 2, x0: w0.x - CELL / 2, x1: w0.x + CELL / 2, h });
                }
                if (!inBounds(GW, GH, x - 1, y) || !open[idx(GW, x - 1, y)]) {
                    vEdges.push({ x: w0.x - CELL / 2, z0: w0.z - CELL / 2, z1: w0.z + CELL / 2, h });
                }
                if (!inBounds(GW, GH, x + 1, y) || !open[idx(GW, x + 1, y)]) {
                    vEdges.push({ x: w0.x + CELL / 2, z0: w0.z - CELL / 2, z1: w0.z + CELL / 2, h });
                }
            }
        }
        const merge = (edges, fixed, lo, hi) => {
            edges.sort((a, b) => a[fixed] - b[fixed] || a[lo] - b[lo]);
            let cur = null;
            const runs = [];
            for (const e of edges) {
                if (cur && e[fixed] === cur[fixed] && e.h === cur.h && e[lo] <= cur[hi] + 1e-6) {
                    cur[hi] = Math.max(cur[hi], e[hi]);
                } else {
                    if (cur) runs.push(cur);
                    cur = { [fixed]: e[fixed], [lo]: e[lo], [hi]: e[hi], h: e.h };
                }
            }
            if (cur) runs.push(cur);
            return runs;
        };
        for (const e of merge(hEdges, 'z', 'x0', 'x1')) {
            wallRuns.push({ x0: e.x0, z0: e.z, x1: e.x1, z1: e.z, h: e.h });
        }
        for (const e of merge(vEdges, 'x', 'z0', 'z1')) {
            wallRuns.push({ x0: e.x, z0: e.z0, x1: e.x, z1: e.z1, h: e.h });
        }
    }

    // --- ceilings: exact slabs over indoor rooms + indoor corridor rects.
    const ceilRects = [];
    {
        const rect = (x, y, w, h, top) => {
            const a = toWorld(x, y), b = toWorld(x + w - 1, y + h - 1);
            ceilRects.push({
                x0: a.x - CELL / 2, z0: a.z - CELL / 2,
                x1: b.x + CELL / 2, z1: b.z + CELL / 2, y: top,
            });
        };
        for (const rm of rooms) {
            if (rm.indoor) rect(rm.x, rm.y, rm.w, rm.h, -1.15 + (rm.zone === 'room' ? 4.2 : 3.2));
        }
        for (const cr of corrRects) {
            if (cr.indoor) rect(cr.x, cr.y, cr.w, cr.h, -1.15 + 3.2);
        }
    }
    // --- route helpers over samples.
    const routeCellsSet = new Set(routeCells.map((c) => idx(GW, c.x, c.y)));
    const distToRoute = (cx, cy) => {
        let best = Infinity;
        for (const k of routeCellsSet) {
            const dx = (k % GW) - cx, dy = Math.floor(k / GW) - cy;
            best = Math.min(best, Math.abs(dx) + Math.abs(dy));
        }
        return best;
    };

    // --- watch cells: per room, the open cell farthest from the walked line
    // that still sees it — the camera's chair, out of the walkway, eyes on
    // the action. Plus a fallback look point on the route.
    const watch = {};
    for (const rm of rooms) {
        const inRoomRoute = [];
        for (let y = rm.y; y < rm.y + rm.h; y++) {
            for (let x = rm.x; x < rm.x + rm.w; x++) {
                if (routeCellsSet.has(idx(GW, x, y))) inRoomRoute.push({ x, y });
            }
        }
        if (!inRoomRoute.length) continue;
        let bestCell = null, bestD = -1;
        for (let y = rm.y; y < rm.y + rm.h; y++) {
            for (let x = rm.x; x < rm.x + rm.w; x++) {
                const d = distToRoute(x, y);
                if (d < 2) continue;
                const sees = inRoomRoute.some((c) => losClear(open, GW, GH, x, y, c.x, c.y));
                if (!sees) continue;
                if (d > bestD) { bestD = d; bestCell = { x, y }; }
            }
        }
        if (!bestCell) continue;
        let lookCell = inRoomRoute[0], lookD = Infinity;
        for (const c of inRoomRoute) {
            if (!losClear(open, GW, GH, bestCell.x, bestCell.y, c.x, c.y)) continue;
            const d = Math.hypot(c.x - rm.cx, c.y - rm.cy);
            if (d < lookD) { lookD = d; lookCell = c; }
        }
        const wp = toWorld(bestCell.x, bestCell.y);
        const lp = toWorld(lookCell.x, lookCell.y);
        watch[rm.id] = { x: wp.x, z: wp.z, lookX: lp.x, lookZ: lp.z };
    }

    // --- items.
    const rItems = new Rng((sd ^ 0x171e5) >>> 0 || 1);
    const items = { props: [], torches: [], puddles: [], windows: [], gates: [], gaps: [], patrols: [], vegetation: [], timbers: [] };
    // Boundary planting: bushes, trees and boulders where an outdoor wall
    // would stand — forest edges grow green, castle-wall edges pile rock.
    // Kind and jitter hash from the cell — pure f(cell), no stream.
    const plantAt = (x, y, kind, s, jx, jz) => {
        const p = toWorld(x, y);
        items.vegetation.push({ x: p.x + jx, z: p.z + jz, kind, s });
    };
    for (const { x, y, zone } of vegCells.values()) {
        const hsh = ((x * 73856093) ^ (y * 19349663)) >>> 0;
        const p = toWorld(x, y);
        // Unsigned shifts throughout: signed >> would sign-extend the hash
        // and throw jitter and scale out of range on high-bit cells.
        const jx = (((hsh >>> 0) % 100) / 100 - 0.5) * 0.8;
        const jz = (((hsh >>> 8) % 100) / 100 - 0.5) * 0.8;
        // Theme density: ember barrens plant half the edges; above 1.0 the
        // extra share grows undergrowth beside the main plant. Hash-fraction,
        // so the same cells plant on every run.
        if ((((hsh >>> 24) % 100) / 100) > Math.min(1, theme.vegMul)) continue;
        const rocky = zone === 'wallwalk';
        const kind = rocky
            ? (hsh % 3 === 2 ? 'bush' : 'boulder')
            : (hsh % 3 === 0 ? 'tree' : 'bush');
        const sc = 0.8 + (((hsh >>> 16) % 100) / 100) * 0.6;
        plantAt(x, y, kind, sc, jx, jz);
        if (theme.vegMul > 1 && (((hsh >>> 20) % 100) / 100) < theme.vegMul - 1) {
            plantAt(x, y, 'bush', sc * 0.6, -jx * 0.5, -jz * 0.5);
        }
    }
    // Coverage guarantee: thinning must never leave an outdoor edge bare.
    // Sweep every open-outdoor edge; plant a bush on the solid neighbour
    // wherever no plant stands within reach. Fixed iteration order, one
    // plant per solid cell, so the fill is as deterministic as the rest.
    const filled = new Set();
    for (let y = 0; y < GH; y++) {
        for (let x = 0; x < GW; x++) {
            if (!open[idx(GW, x, y)] || indoorOf[idx(GW, x, y)]) continue;
            const w0 = toWorld(x, y);
            const edges = [
                [w0.x - CELL / 2, w0.z, x - 1, y], [w0.x + CELL / 2, w0.z, x + 1, y],
                [w0.x, w0.z - CELL / 2, x, y - 1], [w0.x, w0.z + CELL / 2, x, y + 1],
            ];
            for (const [ex, ez, nx, ny] of edges) {
                if (inBounds(GW, GH, nx, ny) && open[idx(GW, nx, ny)]) continue;
                if (!inBounds(GW, GH, nx, ny) || filled.has(idx(GW, nx, ny))) continue;
                const covered = items.vegetation.some((v) => Math.hypot(v.x - ex, v.z - ez) < 1.6);
                if (!covered) {
                    filled.add(idx(GW, nx, ny));
                    const np = toWorld(nx, ny);
                    items.vegetation.push({ x: np.x, z: np.z, kind: 'bush', s: 0.9 });
                }
            }
        }
    }
    // Portal first: largest indoor room, the cell farthest off-route. Props
    // placed afterwards keep one cell of clearance round it.
    let portal = null;
    let portalCell = null;
    {
        const indoor = rooms.filter((rm) => rm.indoor).sort((a, b) => (b.w * b.h) - (a.w * a.h));
        const host = indoor[0] || rooms.slice().sort((a, b) => (b.w * b.h) - (a.w * a.h))[0];
        let bc = null, bd = -1;
        for (let y = host.y; y < host.y + host.h; y++) {
            for (let x = host.x; x < host.x + host.w; x++) {
                const d = distToRoute(x, y);
                if (d > bd) { bd = d; bc = { x, y }; }
            }
        }
        if (bc && bd >= 1) {
            portalCell = bc;
            const p = toWorld(bc.x, bc.y);
            // Face the nearest route cell.
            let nc = null, nd = Infinity;
            for (const k of routeCellsSet) {
                const d = Math.hypot((k % GW) - bc.x, Math.floor(k / GW) - bc.y);
                if (d < nd) { nd = d; nc = k; }
            }
            const np = nc !== null ? toWorld(nc % GW, Math.floor(nc / GW)) : { x: p.x, z: p.z - 1 };
            portal = {
                x: p.x, z: p.z,
                yaw: Math.atan2(np.x - p.x, np.z - p.z),
                roomId: host.id,
            };
        }
    }
    // Props: 2-4 per room, off the walked line, clear of the portal.
    for (const rm of rooms) {
        const n = rItems.int(2, 4);
        let placed = 0, guard = 0;
        while (placed < n && guard++ < 60) {
            const x = rItems.int(rm.x, rm.x + rm.w - 1);
            const y = rItems.int(rm.y, rm.y + rm.h - 1);
            if (distToRoute(x, y) < 2) continue;
            if (portalCell && Math.abs(portalCell.x - x) + Math.abs(portalCell.y - y) < 2) continue;
            const p = toWorld(x, y);
            // Theme dressing: each theme restocks the room vocabulary, so an
            // ember vault reads as stalagmites and a flooded hall as furniture.
            const type = rm.indoor
                ? rItems.pick(theme.propIndoor)
                : rItems.pick(theme.propOutdoor);
            items.props.push({ x: p.x, z: p.z, yaw: rItems.next() * Math.PI * 2, type });
            placed++;
        }
    }
    // Route furniture: torches on walls, slits, puddles, gates, gaps, patrols.
    const stepOf = (du) => Math.max(1, Math.round(du / 0.5));
    {
        // Torches every ~7 units on indoor walls — sconces belong on stone,
        // not on open ground (patrol lanterns light the outside instead).
        // Few and steady: a torch every few steps reads as clutter.
        for (let i = 0; i < pts.length && items.torches.length < 18; i += stepOf(7)) {
            const p = pts[i], q = pts[(i + 1) % pts.length];
            const rcx = Math.floor(p.x / CELL + GW / 2);
            const rcy = Math.floor(p.z / CELL + GH / 2);
            if (!inBounds(GW, GH, rcx, rcy) || !indoorOf[idx(GW, rcx, rcy)]) continue;
            const dx = q.x - p.x, dz = q.z - p.z;
            const l = Math.hypot(dx, dz) || 1;
            const px = -dz / l, pz = dx / l;
            for (const side of [1, -1]) {
                const cx = Math.floor((p.x + px * side * 1.2) / CELL + GW / 2);
                const cy = Math.floor((p.z + pz * side * 1.2) / CELL + GH / 2);
                if (!inBounds(GW, GH, cx, cy) || open[idx(GW, cx, cy)]) continue;
                items.torches.push({
                    x: p.x + px * side * 0.9, z: p.z + pz * side * 0.9,
                    yaw: Math.atan2(-px * side, -pz * side),
                    post: false,
                });
                break;
            }
        }
        // Window slits every ~6 units on indoor stretches with a high wall
        // beside the route. Outdoor slits would float above the low parapet
        // walls, so indoor-only (ceilings imply walls tall enough to slit).
        for (let i = 2; i < pts.length && items.windows.length < 20; i += stepOf(6)) {
            const p = pts[i], q = pts[(i + 1) % pts.length];
            const dx = q.x - p.x, dz = q.z - p.z;
            const l = Math.hypot(dx, dz) || 1;
            const px = -dz / l, pz = dx / l;
            const cx = Math.floor((p.x + px * 1.2) / CELL + GW / 2);
            const cy = Math.floor((p.z + pz * 1.2) / CELL + GH / 2);
            if (!inBounds(GW, GH, cx, cy) || open[idx(GW, cx, cy)]) continue;
            const rcx = Math.floor(p.x / CELL + GW / 2);
            const rcy = Math.floor(p.z / CELL + GH / 2);
            if (!inBounds(GW, GH, rcx, rcy) || !indoorOf[idx(GW, rcx, rcy)]) continue;
            items.windows.push({
                x: p.x + px * 0.95, z: p.z + pz * 0.95,
                yaw: Math.atan2(-px, -pz),
            });
        }
        // Puddles spread round the loop, slightly off the walked line —
        // more of them in the flooded theme, fewer in the ember barrens.
        for (let k = 0, nP = Math.max(2, Math.round(4 * theme.puddleMul)); k < nP; k++) {
            const i = Math.floor((k + 0.5) / nP * pts.length) % pts.length;
            const p = pts[i], q = pts[(i + 1) % pts.length];
            const dx = q.x - p.x, dz = q.z - p.z;
            const l = Math.hypot(dx, dz) || 1;
            items.puddles.push({ x: p.x + (-dz / l) * 0.5, z: p.z + (dx / l) * 0.5, r: 0.7 + rItems.next() * 0.4 });
        }
        // Gates where the route enters rooms (roomId flips corridor→room).
        for (let i = 0; i < pts.length && items.gates.length < 4; i++) {
            const prev = sampleRoom[(i + pts.length - 1) % pts.length];
            const cur = sampleRoom[i];
            if (prev !== -1 || cur === -1) continue;
            const s = cum[i];
            if (items.gates.length && s - items.gates[items.gates.length - 1].s < 12) continue;
            const p = pts[i], q = pts[(i + 1) % pts.length];
            items.gates.push({ x: p.x, z: p.z, yaw: Math.atan2(q.x - p.x, q.z - p.z), s });
        }
        // Gaps spread through rooms, off the gates.
        for (let i = 0; i < pts.length && items.gaps.length < 2; i += stepOf(9)) {
            if (sampleRoom[i] === -1) continue;
            const s = cum[i];
            if (items.gates.some((g) => Math.abs(s - g.s) < 6)) continue;
            const p = pts[i], q = pts[(i + 1) % pts.length];
            items.gaps.push({ x: p.x, z: p.z, yaw: Math.atan2(q.x - p.x, q.z - p.z), s });
        }
        // Patrol lanterns stand along the open ground every ~25 units — they
        // are the outdoor light rhythm now that torches stay on stone.
        for (let i = 0; i < pts.length && items.patrols.length < 6; i += stepOf(25)) {
            const cx = Math.floor(pts[i].x / CELL + GW / 2);
            const cy = Math.floor(pts[i].z / CELL + GH / 2);
            if (!inBounds(GW, GH, cx, cy) || indoorOf[idx(GW, cx, cy)]) continue;
            const s = cum[i];
            if (items.patrols.length && s - items.patrols[items.patrols.length - 1].s < 18) continue;
            const p = pts[i], q = pts[(i + 1) % pts.length];
            // Stand beside the route, never in stone: try both shoulders,
            // fall back to the walked line itself.
            const dx = q.x - p.x, dz = q.z - p.z;
            const l = Math.hypot(dx, dz) || 1;
            let px = p.x, pz = p.z;
            for (const side of [1.2, -1.2, 0]) {
                const tx = p.x + (-dz / l) * side, tz = p.z + (dx / l) * side;
                const tcx = Math.floor(tx / CELL + GW / 2), tcy = Math.floor(tz / CELL + GH / 2);
                if (inBounds(GW, GH, tcx, tcy) && open[idx(GW, tcx, tcy)]) {
                    px = tx; pz = tz; break;
                }
            }
            items.patrols.push({ x: px, z: pz, yaw: Math.atan2(q.x - p.x, q.z - p.z), s });
        }

        // Timber framing: oak door frames on every gate (two posts + a
        // lintel the walk passes under) and posts + top plates along a
        // seeded share of indoor wall runs. World-space boxes; the facade
        // builds them with one shared wood material. Counts capped so the
        // mesh budget stays flat across seeds.
        {
            const rTimber = new Rng((sd ^ 0x71be5) >>> 0 || 1);
            for (const g of items.gates) {
                const fx = Math.sin(g.yaw), fz = Math.cos(g.yaw);
                const rx = Math.cos(g.yaw), rz = -Math.sin(g.yaw);
                for (const side of [-1.15, 1.15]) {
                    items.timbers.push({
                        x: g.x + rx * side, y: FLOOR_Y + 1.35, z: g.z + rz * side,
                        sx: 0.24, sy: 2.7, sz: 0.24, yaw: g.yaw,
                    });
                }
                items.timbers.push({
                    x: g.x, y: FLOOR_Y + 2.75, z: g.z,
                    sx: 2.75, sy: 0.32, sz: 0.32, yaw: g.yaw,
                });
            }
            let budget = Math.round(120 * theme.timberMul);
            const order = rTimber.shuffle(wallRuns.slice());
            for (const run of order) {
                if (budget <= 0) break;
                const lenX = run.x1 - run.x0, lenZ = run.z1 - run.z0;
                const len = Math.max(lenX, lenZ);
                if (len < 4 || rTimber.next() > 0.6) continue;
                const alongX = lenX >= lenZ;
                const yaw = alongX ? 0 : Math.PI / 2;
                const n = Math.max(2, Math.floor(len / 3));
                for (let k = 0; k <= n && budget > 0; k++) {
                    const f = n === 0 ? 0.5 : k / n;
                    items.timbers.push({
                        x: run.x0 + lenX * f, y: FLOOR_Y + run.h / 2, z: run.z0 + lenZ * f,
                        sx: 0.3, sy: run.h, sz: 0.3, yaw: 0,
                    });
                    budget--;
                }
                if (budget <= 0) break;
                items.timbers.push({
                    x: (run.x0 + run.x1) / 2, y: FLOOR_Y + run.h - 0.15, z: (run.z0 + run.z1) / 2,
                    sx: len, sy: 0.28, sz: 0.36, yaw,
                });
                budget--;
            }
        }

        // --- cast: entities that live on the map, loot worth stopping for,
        // and the halts where the walk breaks step. All analytic f(t): entity
        // poses are pure functions of time (see entityPose), halts bend the
        // odometer without ever reversing it (see odometer).
        items.entities = [];
        items.loot = [];
        items.halts = [];
        // Nearest route sample (cell, arclength, index) for any cell.
        const cellRouteS = new Map();
        pts.forEach((p, i) => {
            const cx = Math.floor(p.x / CELL + GW / 2);
            const cy = Math.floor(p.z / CELL + GH / 2);
            const k = cy * GW + cx;
            if (inBounds(GW, GH, cx, cy) && !cellRouteS.has(k)) {
                cellRouteS.set(k, { s: cum[i], i });
            }
        });
        const nearRoute = (cx, cy) => {
            let best = null, bd = Infinity;
            for (const [k, v] of cellRouteS) {
                const dx = (k % GW) - cx, dy = Math.floor(k / GW) - cy;
                const d = Math.abs(dx) + Math.abs(dy);
                if (d < bd) { bd = d; best = v; }
            }
            return best ? { d: bd, ...best } : null;
        };
        const routeTangent = (i) => {
            const p = pts[i % pts.length], q = pts[(i + 1) % pts.length];
            const l = Math.hypot(q.x - p.x, q.z - p.z) || 1;
            return { x: (q.x - p.x) / l, z: (q.z - p.z) / l };
        };
        const takenS = [];
        const clearOf = (s, du) => takenS.every((o) => {
            const L = totalLen;
            const d = Math.abs(s - o) % L;
            return Math.min(d, L - d) >= du;
        });
        // Lurkers pace across the walked line, menacing and sidestepped.
        {
            const cands = [];
            for (let y = 0; y < GH && cands.length < 400; y++) {
                for (let x = 0; x < GW; x++) {
                    if (!open[idx(GW, x, y)] || roomId[idx(GW, x, y)] < 0) continue;
                    const nr = nearRoute(x, y);
                    if (!nr || nr.d !== 1) continue;
                    cands.push({ x, y, ...nr });
                }
            }
            const order = rItems.shuffle(cands);
            for (const c of order) {
                if (items.entities.filter((e) => e.kind === 'lurker').length >= 2) break;
                if (!clearOf(c.s, 25)) continue;
                const p = toWorld(c.x, c.y);
                const tn = routeTangent(c.i);
                items.entities.push({
                    kind: 'lurker', x: p.x, z: p.z,
                    yaw: Math.atan2(-tn.z, tn.x),
                    s: c.s, roomId: roomId[idx(GW, c.x, c.y)],
                    ax: -tn.z, az: tn.x, range: 1.2, speed: 0.45,
                    phase: rItems.next() * 2,
                });
                takenS.push(c.s);
            }
        }
        // A sentry stands the first gate; without a gate, a third lurker.
        if (items.gates.length) {
            const g = items.gates[0];
            // Shoulder of the gate: perpendicular of the route heading.
            const px = Math.cos(g.yaw), pz = -Math.sin(g.yaw);
            let sx = g.x + px * 1.5, sz = g.z + pz * 1.5, placed = false;
            for (const side of [1, -1]) {
                const tx = g.x + px * 1.5 * side, tz = g.z + pz * 1.5 * side;
                const tcx = Math.floor(tx / CELL + GW / 2), tcy = Math.floor(tz / CELL + GH / 2);
                if (inBounds(GW, GH, tcx, tcy) && open[idx(GW, tcx, tcy)]) {
                    sx = tx; sz = tz; placed = true; break;
                }
            }
            if (placed) {
                items.entities.push({
                    kind: 'sentry', x: sx, z: sz,
                    yaw: g.yaw + Math.PI,
                    s: g.s, roomId: -1,
                    ax: 0, az: 0, range: 0, speed: 0, phase: 0,
                });
                takenS.push(g.s);
            }
        }
        // Critters dart between hideouts; a wisp drifts for atmosphere.
        {
            const cands = [];
            for (let y = 0; y < GH && cands.length < 400; y++) {
                for (let x = 0; x < GW; x++) {
                    if (!open[idx(GW, x, y)] || roomId[idx(GW, x, y)] < 0) continue;
                    const nr = nearRoute(x, y);
                    if (!nr || nr.d < 2 || nr.d > 3) continue;
                    cands.push({ x, y, ...nr });
                }
            }
            const order = rItems.shuffle(cands);
            for (const c of order) {
                if (items.entities.filter((e) => e.kind === 'critter').length >= 2) break;
                if (!clearOf(c.s, 20)) continue;
                const p = toWorld(c.x, c.y);
                const tn = routeTangent(c.i);
                items.entities.push({
                    kind: 'critter', x: p.x, z: p.z,
                    yaw: Math.atan2(tn.x, tn.z),
                    s: c.s, roomId: roomId[idx(GW, c.x, c.y)],
                    ax: tn.x, az: tn.z, range: 2.0, speed: 1.4,
                    phase: rItems.next() * 2,
                });
                takenS.push(c.s);
            }
            const wcands = [];
            for (let y = 0; y < GH && wcands.length < 200; y++) {
                for (let x = 0; x < GW; x++) {
                    if (!open[idx(GW, x, y)] || roomId[idx(GW, x, y)] < 0) continue;
                    const nr = nearRoute(x, y);
                    if (!nr || nr.d < 2) continue;
                    wcands.push({ x, y, ...nr });
                }
            }
            if (wcands.length) {
                const c = rItems.pick(wcands);
                const p = toWorld(c.x, c.y);
                items.entities.push({
                    kind: 'wisp', x: p.x, z: p.z, yaw: 0,
                    s: c.s, roomId: roomId[idx(GW, c.x, c.y)],
                    ax: 0, az: 0, range: 1.0, speed: 0.5,
                    phase: rItems.next() * 2,
                });
            }
        }
        // Loot worth stopping for: room cells a step off the walked line,
        // spaced round the loop. Every cache earns its halt below.
        {
            const cands = [];
            for (let y = 0; y < GH && cands.length < 400; y++) {
                for (let x = 0; x < GW; x++) {
                    if (!open[idx(GW, x, y)] || roomId[idx(GW, x, y)] < 0) continue;
                    const nr = nearRoute(x, y);
                    if (!nr || nr.d < 1 || nr.d > 2) continue;
                    if (portalCell && Math.abs(portalCell.x - x) + Math.abs(portalCell.y - y) < 2) continue;
                    cands.push({ x, y, ...nr });
                }
            }
            const kinds = rItems.shuffle(['cache', 'relic', 'hoard']);
            const order = rItems.shuffle(cands);
            for (const c of order) {
                if (items.loot.length >= 3) break;
                if (!clearOf(c.s, 30)) continue;
                const p = toWorld(c.x, c.y);
                // Face the nearest route point.
                const rp = pts[c.i % pts.length];
                items.loot.push({
                    kind: kinds[items.loot.length % kinds.length],
                    x: p.x, z: p.z,
                    yaw: Math.atan2(rp.x - p.x, rp.z - p.z),
                    s: c.s, roomId: roomId[idx(GW, c.x, c.y)],
                });
                takenS.push(c.s);
            }
            // Halts: one pause per cache, spaced by construction (loot holds
            // 30u apart, pauses need 15) so pauses never overlap — the
            // odometer can hold or advance, never retreat.
            for (const l of items.loot) {
                items.halts.push({ s: l.s, dur: 2.2 });
            }
        }
    }

    return {
        seed: sd, w: GW, h: GH, cell: CELL, grid: open, indoor: indoorOf,
        rooms: rooms.map((rm) => ({ id: rm.id, x: rm.x, y: rm.y, w: rm.w, h: rm.h, zone: rm.zone, indoor: rm.indoor })),
        wallRuns, ceilRects,
        route: { pts, cum, totalLen, roomIds: sampleRoom, zones: sampleZone },
        items, portal, watch, character, theme: themeName,
    };
}

// ------------------------------------------------------------- queries

function locate(plan, s) {
    const { pts, cum } = plan.route;
    const L = plan.route.totalLen;
    const q = ((s % L) + L) % L;
    let lo = 0, hi = cum.length - 1;
    while (lo < hi - 1) {
        const mid = (lo + hi) >> 1;
        if (cum[mid] <= q) lo = mid;
        else hi = mid;
    }
    const i = lo % pts.length;
    const p = pts[i], nq = pts[(i + 1) % pts.length];
    const span = cum[lo + 1] - cum[lo] || 1;
    const f = Math.max(0, Math.min(1, (q - cum[lo]) / span));
    return {
        x: p.x + (nq.x - p.x) * f,
        z: p.z + (nq.z - p.z) * f,
        yaw: Math.atan2(nq.x - p.x, nq.z - p.z),
        index: i,
    };
}

/** World position + heading at arclength s (wraps). Pure, no state. */
export function pathAt(plan, s) {
    const here = locate(plan, s);
    const ahead = locate(plan, s + 0.75);
    return {
        x: here.x,
        z: here.z,
        yaw: Math.atan2(ahead.x - here.x, ahead.z - here.z),
    };
}

/** Room id at arclength s, or -1 in a corridor. */
export function roomAt(plan, s) {
    return plan.route.roomIds[locate(plan, s).index];
}

/** Zone name at arclength s. */
export function zoneAt(plan, s) {
    return plan.route.zones[locate(plan, s).index];
}

/**
 * The interrupted odometer: a constant-gait walk that pauses at halts.
 *
 * heroS(t) = cruise·(t − paused(t)), paused(t) = Σ clamp(t − s_h/cruise, 0, dur_h).
 * Each halt freezes the walk for dur seconds at exactly its arclength, then
 * resumes — velocity is piecewise {0, cruise}, so the walk can hold or
 * advance but never retreat, whatever the params. Pure f(t): seeks agree
 * with playback. Halts are spaced ≥15u apart at plan time (see items.halts),
 * so pauses never overlap and the bound holds a priori.
 */
export function odometer(cruise, halts, L, t) {
    const c = Math.max(0.05, cruise);
    let paused = 0;
    for (const h of halts || []) {
        paused += Math.max(0, Math.min(t - h.s / c, h.dur));
    }
    return (((c * (t - paused)) % L) + L) % L;
}

function wrapDist(a, b, L) {
    const d = Math.abs(a - b) % L;
    return Math.min(d, L - d);
}

function tri01(x) {
    const u = ((x % 2) + 2) % 2;
    return u < 1 ? u : 2 - u;
}

function triSign(x) {
    const u = ((x % 2) + 2) % 2;
    return u < 1 ? 1 : -1;
}

function yawLerp(a, b, k) {
    // Shortest-arc blend of two headings.
    const sa = Math.sin(a), ca = Math.cos(a);
    const sb = Math.sin(b), cb = Math.cos(b);
    return Math.atan2(sa + (sb - sa) * k, ca + (cb - ca) * k);
}

/**
 * Where an entity is and how alarmed, at time t with the hero at (heroS,
 * heroX, heroZ). Pure f(...) — analytic triangle gaits, gaussian proximity,
 * no integration, so every frame renders identically from any seek.
 *
 * Returns { x, z, yaw, alert } with alert ∈ [0, 1]: 1 while the hero is on
 * top of it, 0 beyond 8 units of route behind/ahead.
 */
export function entityPose(e, t, heroS, heroX, heroZ, L) {
    const prox = (e.s === undefined || e.s === null || L <= 0)
        ? 0
        : smooth01(1 - wrapDist(heroS, e.s, L) / 8);
    const faceHero = Math.atan2(heroX - e.x, heroZ - e.z);
    if (e.kind === 'lurker') {
        const ph = t * e.speed + e.phase;
        const u = tri01(ph) * 2 - 1;
        const paceYaw = Math.atan2(e.ax * triSign(ph), e.az * triSign(ph));
        const amp = e.range * (1 - prox * 0.6);
        return {
            x: e.x + e.ax * u * amp,
            z: e.z + e.az * u * amp,
            yaw: yawLerp(paceYaw, faceHero, prox),
            alert: prox,
        };
    }
    if (e.kind === 'sentry') {
        return { x: e.x, z: e.z, yaw: yawLerp(e.yaw, faceHero, prox), alert: prox };
    }
    if (e.kind === 'critter') {
        const ph = t * e.speed + e.phase;
        const u = tri01(ph) * 2 - 1;
        let fx = e.x + e.ax * u * e.range;
        let fz = e.z + e.az * u * e.range;
        // Flees the hero's lantern: offset away, scaled by proximity.
        const dx = fx - heroX, dz = fz - heroZ;
        const dl = Math.hypot(dx, dz);
        const flee = prox * 1.5;
        if (dl > 1e-4) { fx += (dx / dl) * flee; fz += (dz / dl) * flee; }
        else { fx += e.az * flee; fz += -e.ax * flee; }
        return {
            x: fx, z: fz,
            yaw: Math.atan2(e.ax * triSign(ph), e.az * triSign(ph)),
            alert: prox,
        };
    }
    // wisp: slow orbit that leans toward a nearby hero.
    const a = t * e.speed + e.phase;
    const r = e.range * (1 - prox * 0.4);
    let wx = e.x + Math.cos(a) * r;
    let wz = e.z + Math.sin(a * 0.9) * r;
    if (prox > 0) {
        const dx = heroX - e.x, dz = heroZ - e.z;
        const dl = Math.hypot(dx, dz) || 1;
        wx += (dx / dl) * prox * 1.2;
        wz += (dz / dl) * prox * 1.2;
    }
    return { x: wx, z: wz, yaw: 0, alert: prox };
}