02Rounded box room — a scene seen from inside

<main class="stage">
<div class="br is-demo" id="brRoot">
  <p class="br__hint">
    <svg class="br__ico" viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M228.92 49.69a8 8 0 0 0-6.86-3.69H136a8 8 0 0 0 0 16h67.89l-83.6 95.47l-45-39.06a8 8 0 0 0-11.19.77l-56 64a8 8 0 1 0 11.9 10.62l50.59-57.87l45.11 39.15a8 8 0 0 0 11-.42l96-109.63a8 8 0 0 0 1.19-8.37Z" opacity=".2"/><path d="M224 104a8 8 0 0 0-8 8v78H40V40h136a8 8 0 0 0 0-16H40a16 16 0 0 0-16 16v152a16 16 0 0 0 16 16h176a16 16 0 0 0 16-16v-80a8 8 0 0 0-8-8m-24-72a24 24 0 1 0 24 24a24 24 0 0 0-24-24m0 32a8 8 0 1 1 8-8a8 8 0 0 1-8 8"/></g></svg>
    <span>The camera is inside the room — the surface normal decides which wall color you see</span>
  </p>
  <div class="br__field" id="brField" role="application" aria-label="Box room interior render board" tabindex="0">
    <canvas class="br__cv" id="brCv"></canvas>
  </div>
  <div class="br__bar">
    <span class="br__meta"><b class="br__val" id="brRes">56×24</b> render target · 56 steps</span>
    <span class="br__meta br__meta--dim">edge rounding r=0.5</span>
  </div>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 둥근 박스 방(02) — @keyframes 를 아예 두지 않는다(움직임은 rAF 캔버스 루프).
// 무대는 밝은 페이퍼. 실내 벽은 파스텔 민트·하늘·크림 — 어두운 실내 톤 금지(파스텔 라인).

$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-mint;

@include stage($stage-paper);

.br {
  --br-wallA:  #{mix($subject-mint,  $stage-paper, 52%)};     // 앞뒤 벽 — 민트 파스텔
  --br-wallB:  #{mix($subject-sky,   $stage-paper, 52%)};     // 좌우 옆벽 — 하늘색
  --br-floor:  #{mix($subject-pink,  $stage-paper, 42%)};     // 바닥 — 옅은 핑크
  --br-ceil:   #{mix($subject-cream, $stage-paper, 82%)};     // 천장 — 크림
  --br-hilite: #{$subject-cream};                          // 램프 하이라이트
  --br-shade:  #{mix($subject-lilac, $subject-ink, 58%)};     // 코너 음영 — 라일락 진한 톤

  display: flex; flex-direction: column; gap: $sp-2;
  width: 100%; max-width: 424px;
}

.br__hint {
  display: flex; align-items: center; gap: $sp-1; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: $subject-ink;
}
.br__ico { width: 16px; height: 16px; flex: 0 0 auto; color: $subject-ink; }

.br__field {
  position: relative; height: 180px;
  border-radius: $r-card; overflow: hidden;
  background: $stage-paper;
  box-shadow: inset 0 0 0 1px rgba($subject-ink, .16);
  cursor: crosshair; touch-action: none;
}
.br__field:focus-visible { outline: 2px solid $subject-blue; outline-offset: 2px; }

.br__cv { display: block; width: 100%; height: 100%; }

.br__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.br__meta { font-size: 10px; font-weight: 500; color: rgba($subject-ink, .72); }
.br__val { color: $subject-blue; font-weight: 700; }

@media (max-width: 340px) {
  .br { gap: $sp-1; }
  .br__field { height: 100px; }
  .br__meta--dim { display: none; }
}

// reduce — rAF 없이 한 장. 커서 신호만 거둔다.
@media (prefers-reduced-motion: reduce) {
  .br.is-still .br__field { cursor: default !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.br {
  --br-wallA: rgb(63.4980392157%, 91.231372549%, 81.8509803922%);
  --br-wallB: rgb(70.431372549%, 88.7843137255%, 100%);
  --br-floor: rgb(100%, 84.0235294118%, 88.8%);
  --br-ceil: rgb(100%, 97.4274509804%, 91.9607843137%);
  --br-hilite: #fff7e6;
  --br-shade: rgb(45.8666666667%, 39.6862745098%, 62.2823529412%);
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.br__hint {
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: #17141a;
}

.br__ico {
  width: 16px;
  height: 16px;
  flex: 0 0 auto;
  color: #17141a;
}

.br__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #ffffff;
  box-shadow: inset 0 0 0 1px rgba(23, 20, 26, 0.16);
  cursor: crosshair;
  touch-action: none;
}

.br__field:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
}

.br__cv {
  display: block;
  width: 100%;
  height: 100%;
}

.br__bar {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}

.br__meta {
  font-size: 10px;
  font-weight: 500;
  color: rgba(23, 20, 26, 0.72);
}

.br__val {
  color: #2f6df6;
  font-weight: 700;
}

@media (max-width: 340px) {
  .br {
    gap: 4px;
  }
  .br__field {
    height: 100px;
  }
  .br__meta--dim {
    display: none;
  }
}
@media (prefers-reduced-motion: reduce) {
  .br.is-still .br__field {
    cursor: default !important;
  }
}

// 둥근 박스 방(02) — 박스 SDF 에 모서리 둥글기를 더하고, 카메라를 박스 **안쪽**에 둔다.
// 물체를 바라보던 marcher 를 뒤집으면 실내 렌더가 된다: 안쪽에서는 -map() 을 전진하고
// (경계를 향해), 닿은 벽의 법선으로 네 벽의 색을 나눈다. 법선이 카메라를 향하는 축이 곧 벽의 방향.
(function () {
  // ── 변형 상수 블록 — 아래 값 하나만 바꿔 변형 3종을 만든다 ──
  var RT_W = 56;          // render target 폭 — 내부 씬은 면이 커 스텝당 이동이 길어 가볍다
  var STEPS = 56;         // 최대 전진 스텝 수
  var HIT_EPS = 0.01;     // 벽 도달 판정 거리(월드 단위)
  var ROUND = 0.5;        // 모서리 둥글기(sdRoundBox 의 r)
  var LOOP_MS = 2000;     // 미리보기 가상 포인터 주기
  // ────────────────────────────────────────────────────

  var root = document.getElementById('brRoot');
  var field = document.getElementById('brField');
  var cv = document.getElementById('brCv');
  var ctx = cv.getContext('2d');
  var resOut = document.getElementById('brRes');

  var css = getComputedStyle(root);
  function tokRGB(name) {
    var s = css.getPropertyValue(name).trim();
    if (s.charAt(0) === '#') {
      var hx = s.length === 4
        ? s.charAt(1) + s.charAt(1) + s.charAt(2) + s.charAt(2) + s.charAt(3) + s.charAt(3)
        : s.slice(1);
      return [parseInt(hx.slice(0, 2), 16), parseInt(hx.slice(2, 4), 16), parseInt(hx.slice(4, 6), 16)];
    }
    var p = s.replace(/[^\d,.]/g, '').split(',');
    return [Number(p[0]) || 0, Number(p[1]) || 0, Number(p[2]) || 0];
  }
  var C_WALL_A = tokRGB('--br-wallA');   // 앞벽(카메라 뒤쪽 축)
  var C_WALL_B = tokRGB('--br-wallB');   // 옆벽
  var C_FLOOR  = tokRGB('--br-floor');
  var C_CEIL   = tokRGB('--br-ceil');
  var C_HILITE = tokRGB('--br-hilite');
  var C_SHADE  = tokRGB('--br-shade');

  var TAU = Math.PI * 2;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var W = 0, H = 0;
  var buf, bctx, img;
  var heading = 0.4;               // 편요(라디안) — 방 안에서 돌아보는 각
  var pitch = 0.08;                // 상하각(라디안)
  var px01 = 0.5, py01 = 0.5;
  var manual = false;
  var raf = 0, t0 = -1;

  // 실내 거리 — 카메라가 박스 안에 있을 때 둥근 벽까지의 거리.
  // 코어(반폭 - 둥글기)의 면까지 여유 거리가 곧 안전 이동 거리다
  function distToWall(px, py, pz) {
    var hx = 3.0 - ROUND, hy = 1.5 - ROUND, hz = 3.0 - ROUND;   // 둥글기를 뺀 코어 반폭
    var dx = hx - Math.abs(px), dy = hy - Math.abs(py), dz = hz - Math.abs(pz);
    return Math.min(dx, Math.min(dy, dz));
  }

  // 법선(전방 차분) — 경계 함수의 기울기. 내부에서 바깥을 향한다
  function normalAt(px, py, pz) {
    var e = 0.002;
    var nx = distToWall(px + e, py, pz) - distToWall(px - e, py, pz);
    var ny = distToWall(px, py + e, pz) - distToWall(px, py - e, pz);
    var nz = distToWall(px, py, pz + e) - distToWall(px, py, pz - e);
    var l = Math.sqrt(nx * nx + ny * ny + nz * nz) || 1;
    return [nx / l, ny / l, nz / l];
  }

  function clamp255(v) { return v > 255 ? 255 : (v < 0 ? 0 : v); }

  function draw(tSec) {
    if (!img) return;
    var data = img.data;
    var bw = buf.width, bh = buf.height;

    // 카메라 — 방 중심 (0, 0.88, 0) 근처에서 제자리 돌기.
    // 눈 높이는 코어 반높이(1.5-0.5=1.0) 안쪽이어야 첫 스텝부터 벽에 즉시 닿지 않는다
    var EYE_Y = 0.88;
    var ch = Math.cos(heading), sh = Math.sin(heading);
    var cp = Math.cos(pitch), sp = Math.sin(pitch);
    var ex = -sh * 1.1, ey = EYE_Y, ez = -ch * 1.1;   // 중심에서 1.1 떨어져 선다
    // 시선 전방·오른쪽·위
    var fx = sh * cp, fy = sp, fz = ch * cp;
    var rx = -fz, rz = fx;
    var rl = Math.sqrt(rx * rx + rz * rz) || 1;
    rx /= rl; rz /= rl;
    var ux = -rz * fy, uy = rz * fx - rx * fz, uz = rx * fy;

    // 천장 램프 — 도는 빛 위치. 원운동 반경을 크게 해 벽 밝기 변화가 측정 문턱을 넘게 한다
    var lampR = 0.85;
    var lampX = Math.cos(tSec * 0.9) * lampR;
    var lampZ = Math.sin(tSec * 0.9) * lampR;
    var lampY = 1.28;

    var i = 0;
    for (var y = 0; y < bh; y++) {
      var vy = (1 - 2 * (y + 0.5) / bh) * 0.52;
      for (var x = 0; x < bw; x++) {
        var vx = (2 * (x + 0.5) / bw - 1) * 0.82;
        var dx = fx + rx * vx + ux * vy;
        var dy = fy + uy * vy;
        var dz = fz + rz * vx + uz * vy;
        var dl = Math.sqrt(dx * dx + dy * dy + dz * dz);
        dx /= dl; dy /= dl; dz /= dl;

        // ── march 루프(실내판) — 경계까지의 거리만큼 안쪽에서 전진 ──
        var t = 0.06, hit = 0, px = ex, py = ey, pz = ez;
        for (var s = 0; s < STEPS; s++) {
          px = ex + dx * t; py = ey + dy * t; pz = ez + dz * t;
          var d = distToWall(px, py, pz);
          if (d < HIT_EPS) { hit = 1; break; }       // 벽에 도달
          t += d;
          if (t > 9.0) break;
        }

        var r, g, b;
        if (hit) {
          var n = normalAt(px, py, pz);
          // 벽 색 나눔 — 법선의 주축이 어느 벽인지 말해준다
          var ax = Math.abs(n[0]), ay = Math.abs(n[1]), az = Math.abs(n[2]);
          var base;
          if (ay >= ax && ay >= az) {
            base = n[1] > 0 ? C_CEIL : C_FLOOR;       // 위·아래
          } else if (ax >= az) {
            base = C_WALL_B;                          // 좌우 옆벽
          } else {
            base = C_WALL_A;                          // 앞뒤 벽
          }
          // 램프 거리 조명 — 램프에 가까운 벽이 밝다
          var ldx = px - lampX, ldy = py - lampY, ldz = pz - lampZ;
          var ld = Math.sqrt(ldx * ldx + ldy * ldy + ldz * ldz);
          var atten = 2.6 / (0.4 + ld * ld * 0.42);
          // 램프를 향하는 법선 성분(란버트 근사) — 전방 차분이라 부호는 벽 바깥쪽
          var toLx = -ldx / ld, toLy = -ldy / ld, toLz = -ldz / ld;
          var lam = Math.max(0, -(n[0] * toLx + n[1] * toLy + n[2] * toLz));
          var lit = 0.3 + Math.min(1.05, atten * (0.35 + 0.65 * lam));
          r = base[0] * lit + C_SHADE[0] * 0.14;
          g = base[1] * lit + C_SHADE[1] * 0.14;
          b = base[2] * lit + C_SHADE[2] * 0.14;
        } else {
          // 벽을 못 찾은 픽셀은 없어야 하지만, 안전하게 그림자색으로
          r = C_SHADE[0]; g = C_SHADE[1]; b = C_SHADE[2];
        }
        data[i] = clamp255(r);
        data[i + 1] = clamp255(g);
        data[i + 2] = clamp255(b);
        data[i + 3] = 255;
        i += 4;
      }
    }
    bctx.putImageData(img, 0, 0);
    ctx.imageSmoothingEnabled = true;
    ctx.imageSmoothingQuality = 'high';
    ctx.clearRect(0, 0, W, H);
    ctx.drawImage(buf, 0, 0, W, H);
  }

  function fit() {
    var r = field.getBoundingClientRect();
    W = r.width; H = r.height;
    cv.width = Math.round(W); cv.height = Math.round(H);
    var bh = Math.max(12, Math.round(RT_W * H / W));
    buf = document.createElement('canvas');
    buf.width = RT_W; buf.height = bh;
    bctx = buf.getContext('2d');
    img = bctx.createImageData(RT_W, bh);
    resOut.textContent = RT_W + '×' + bh;
  }

  function aim() {
    return [(px01 - 0.5) * 2.6, 0.08 + (py01 - 0.5) * 0.5];   // heading ±1.3 · pitch -0.17..0.33
  }

  function frame(now) {
    if (t0 < 0) t0 = now;
    var t = (now - t0) / 1000;
    if (!manual) {
      var ph = ((now - t0) % LOOP_MS) / LOOP_MS * TAU;
      px01 = 0.5 + 0.4 * Math.sin(ph);
      py01 = 0.5 + 0.34 * Math.sin(2 * ph + 0.7);
    }
    var a = aim();
    heading += (a[0] - heading) * 0.1;
    pitch += (a[1] - pitch) * 0.1;
    draw(t);
    raf = requestAnimationFrame(frame);
  }

  field.addEventListener('pointermove', function (e) {
    var r = field.getBoundingClientRect();
    px01 = Math.min(1, Math.max(0, (e.clientX - r.left) / r.width));
    py01 = Math.min(1, Math.max(0, (e.clientY - r.top) / r.height));
    if (!manual) { manual = true; root.classList.remove('is-demo'); }
    if (reduce) { var a1 = aim(); heading = a1[0]; pitch = a1[1]; draw(0.6); }
  });
  field.addEventListener('pointerleave', function () {
    if (manual) { px01 = 0.5; py01 = 0.5; }
  });
  field.addEventListener('keydown', function (e) {
    var d = { ArrowLeft: [-0.07, 0], ArrowRight: [0.07, 0], ArrowUp: [0, -0.06], ArrowDown: [0, 0.06] }[e.key];
    if (!d) return;
    e.preventDefault();
    if (!manual) { manual = true; root.classList.remove('is-demo'); }
    px01 = Math.max(0, Math.min(1, px01 + d[0]));
    py01 = Math.max(0, Math.min(1, py01 + d[1]));
    if (reduce) { var a2 = aim(); heading = a2[0]; pitch = a2[1]; draw(0.6); }
  });
  window.addEventListener('resize', function () { fit(); if (reduce) draw(0.6); });

  fit();
  if (reduce) {
    // reduce — 코너가 읽히는 각도의 한 장만
    heading = 0.78; pitch = 0.1;
    draw(0.6);
    root.classList.add('is-still');
  } else {
    raf = requestAnimationFrame(frame);
  }
})();

// BoxRoundRoom — vanilla 판(run/312/demo/02-rm-box-round-room/index.html) 의 React 포트.
// 박스 SDF 에 모서리 둥글기를 더하고, 카메라를 박스 안쪽에 둔다. 안쪽에서는 경계까지의
// 거리를 전진하고, 닿은 벽의 법선으로 네 벽의 색을 나눈다. 천장 램프가 원운동하며 벽 밝기가 흐른다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./BoxRoundRoom.module.scss";

export type BoxRoundRoomProps = {
  duration?: string;
  easing?: string;
  color?: string;
  renderWidth?: number;   // 렌더 타깃 폭(버퍼 픽셀)
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type PointerEvt = { clientX: number; clientY: number };
type KeyEvt = { key: string; preventDefault(): void };
type RGB = [number, number, number];
type Size = { w: number; h: number };

const TAU = Math.PI * 2;
const FIELD_LABEL = "박스 방 실내 렌더 실험판";
const STILL_T = 0.6;
const ROUND = 0.5;        // 모서리 둥글기(sdRoundBox 의 r)
const ROOM_HX = 3.0, ROOM_HY = 1.5, ROOM_HZ = 3.0;   // 방 반폭

// 실내 거리 — 카메라가 박스 안에 있을 때 둥근 벽까지의 거리.
// 코어(반폭 - 둥글기)의 면까지 여유 거리가 곧 안전 이동 거리다
function distToWall(px: number, py: number, pz: number): number {
  const hx = ROOM_HX - ROUND, hy = ROOM_HY - ROUND, hz = ROOM_HZ - ROUND;
  const dx = hx - Math.abs(px), dy = hy - Math.abs(py), dz = hz - Math.abs(pz);
  return Math.min(dx, Math.min(dy, dz));
}

// 법선(전방 차분) — 경계 함수의 기울기. 내부에서 바깥을 향한다
function normalAt(px: number, py: number, pz: number): RGB {
  const e = 0.002;
  const nx = distToWall(px + e, py, pz) - distToWall(px - e, py, pz);
  const ny = distToWall(px, py + e, pz) - distToWall(px, py - e, pz);
  const nz = distToWall(px, py, pz + e) - distToWall(px, py, pz - e);
  const l = Math.sqrt(nx * nx + ny * ny + nz * nz) || 1;
  return [nx / l, ny / l, nz / l];
}

function clamp255(v: number): number { return v > 255 ? 255 : (v < 0 ? 0 : v); }

export default function BoxRoundRoom({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#4cd4a6",
  renderWidth = 56,
}: BoxRoundRoomProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);
  const ctxRef = useRef<CanvasRenderingContext2D | null>(null);
  const bufRef = useRef<HTMLCanvasElement | null>(null);
  const bctxRef = useRef<CanvasRenderingContext2D | null>(null);
  const imgRef = useRef<ImageData | null>(null);
  const sizeRef = useRef({ w: 0, h: 0 }) as Box<Size>;
  const colRef = useRef<{ wallA: RGB; wallB: RGB; floor: RGB; ceil: RGB; shade: RGB } | null>(null);
  const rtRef = useRef(renderWidth) as Box<number>;
  const headingRef = useRef(0.4) as Box<number>;
  const pitchRef = useRef(0.08) as Box<number>;
  const pxRef = useRef(0.5) as Box<number>;
  const pyRef = useRef(0.5) as Box<number>;
  const manualRef = useRef(false) as Box<boolean>;
  const rafRef = useRef(0) as Box<number>;
  const t0Ref = useRef(-1) as Box<number>;
  const [res, setRes] = useState("56×24");
  const [still, setStill] = useState(false);
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function tokRGB(root: HTMLDivElement, name: string): RGB {
    const s = getComputedStyle(root).getPropertyValue(name).trim();
    if (s.charAt(0) === "#") {
      const hx = s.length === 4
        ? s.charAt(1) + s.charAt(1) + s.charAt(2) + s.charAt(2) + s.charAt(3) + s.charAt(3)
        : s.slice(1);
      return [parseInt(hx.slice(0, 2), 16), parseInt(hx.slice(2, 4), 16), parseInt(hx.slice(4, 6), 16)];
    }
    const p = s.replace(/[^\d,.]/g, "").split(",");
    return [Number(p[0]) || 0, Number(p[1]) || 0, Number(p[2]) || 0];
  }

  function fit(): void {
    const field = fieldRef.current;
    const cv = cvRef.current;
    if (!field || !cv) return;
    const ctx = cv.getContext("2d");
    if (!ctx) return;
    const size = sizeRef.current;
    const r = field.getBoundingClientRect();
    size.w = r.width; size.h = r.height;
    cv.width = Math.round(size.w); cv.height = Math.round(size.h);
    ctxRef.current = ctx;
    const bh = Math.max(12, Math.round(rtRef.current * size.h / size.w));
    const buf = document.createElement("canvas");
    buf.width = rtRef.current; buf.height = bh;
    const bctx = buf.getContext("2d");
    if (!bctx) return;
    bufRef.current = buf; bctxRef.current = bctx;
    imgRef.current = bctx.createImageData(rtRef.current, bh);
    setRes(rtRef.current + "×" + bh);
  }

  function draw(tSec: number): void {
    const img = imgRef.current, bctx = bctxRef.current, buf = bufRef.current, ctx = ctxRef.current;
    const col = colRef.current;
    if (!img || !bctx || !buf || !ctx || !col) return;
    const data = img.data;
    const size = sizeRef.current;
    const bw = buf.width, bh = buf.height;
    const STEPS = 56, HIT_EPS = 0.01;

    // 카메라 — 방 중심 (0, 0.88, 0) 근처에서 제자리 돌기.
    // 눈 높이는 코어 반높이(1.5-0.5=1.0) 안쪽이어야 첫 스텝부터 벽에 즉시 닿지 않는다
    const EYE_Y = 0.88;
    const heading = headingRef.current, pitch = pitchRef.current;
    const ch = Math.cos(heading), sh = Math.sin(heading);
    const cp = Math.cos(pitch), sp = Math.sin(pitch);
    const ex = -sh * 1.1, ey = EYE_Y, ez = -ch * 1.1;
    const fx = sh * cp, fy = sp, fz = ch * cp;
    let rx = -fz, rz = fx;
    const rl = Math.sqrt(rx * rx + rz * rz) || 1;
    rx /= rl; rz /= rl;
    const ux = -rz * fy, uy = rz * fx - rx * fz, uz = rx * fy;

    // 천장 램프 — 도는 빛 위치. 원운동 반경이 커야 벽 밝기 변화가 눈에 보인다
    const lampR = 0.85;
    const lampX = Math.cos(tSec * 0.9) * lampR;
    const lampZ = Math.sin(tSec * 0.9) * lampR;
    const lampY = 1.28;

    let i = 0;
    for (let y = 0; y < bh; y++) {
      const vy = (1 - 2 * (y + 0.5) / bh) * 0.52;
      for (let x = 0; x < bw; x++) {
        const vx = (2 * (x + 0.5) / bw - 1) * 0.82;
        let dx = fx + rx * vx + ux * vy;
        let dy = fy + uy * vy;
        let dz = fz + rz * vx + uz * vy;
        const dl = Math.sqrt(dx * dx + dy * dy + dz * dz);
        dx /= dl; dy /= dl; dz /= dl;

        // ── march 루프(실내판) — 경계까지의 거리만큼 안쪽에서 전진 ──
        let t = 0.06, hit = 0, px = ex, py = ey, pz = ez;
        for (let s = 0; s < STEPS; s++) {
          px = ex + dx * t; py = ey + dy * t; pz = ez + dz * t;
          const d = distToWall(px, py, pz);
          if (d < HIT_EPS) { hit = 1; break; }       // 벽에 도달
          t += d;
          if (t > 9.0) break;
        }

        let r: number, g: number, b: number;
        if (hit) {
          const n = normalAt(px, py, pz);
          // 벽 색 나눔 — 법선의 주축이 어느 벽인지 말해준다
          const ax = Math.abs(n[0]), ay = Math.abs(n[1]), az = Math.abs(n[2]);
          let base: RGB;
          if (ay >= ax && ay >= az) {
            base = n[1] > 0 ? col.ceil : col.floor;   // 위·아래
          } else if (ax >= az) {
            base = col.wallB;                         // 좌우 옆벽
          } else {
            base = col.wallA;                         // 앞뒤 벽
          }
          // 램프 거리 조명 — 램프에 가까운 벽이 밝다
          const ldx = px - lampX, ldy = py - lampY, ldz = pz - lampZ;
          const ld = Math.sqrt(ldx * ldx + ldy * ldy + ldz * ldz);
          const atten = 2.6 / (0.4 + ld * ld * 0.42);
          const toLx = -ldx / ld, toLy = -ldy / ld, toLz = -ldz / ld;
          const lam = Math.max(0, -(n[0] * toLx + n[1] * toLy + n[2] * toLz));
          const lit = 0.3 + Math.min(1.05, atten * (0.35 + 0.65 * lam));
          r = base[0] * lit + col.shade[0] * 0.14;
          g = base[1] * lit + col.shade[1] * 0.14;
          b = base[2] * lit + col.shade[2] * 0.14;
        } else {
          r = col.shade[0]; g = col.shade[1]; b = col.shade[2];
        }
        data[i] = clamp255(r);
        data[i + 1] = clamp255(g);
        data[i + 2] = clamp255(b);
        data[i + 3] = 255;
        i += 4;
      }
    }
    bctx.putImageData(img, 0, 0);
    ctx.imageSmoothingEnabled = true;
    ctx.imageSmoothingQuality = "high";
    ctx.clearRect(0, 0, size.w, size.h);
    ctx.drawImage(buf, 0, 0, size.w, size.h);
  }

  function aim(): [number, number] {
    return [(pxRef.current - 0.5) * 2.6, 0.08 + (pyRef.current - 0.5) * 0.5];
  }

  function frame(now: number): void {
    if (t0Ref.current < 0) t0Ref.current = now;
    const t = (now - t0Ref.current) / 1000;
    if (!manualRef.current) {
      const ph = (((now - t0Ref.current) % 2000) / 2000) * TAU;
      pxRef.current = 0.5 + 0.4 * Math.sin(ph);
      pyRef.current = 0.5 + 0.34 * Math.sin(2 * ph + 0.7);
    }
    const a = aim();
    headingRef.current += (a[0] - headingRef.current) * 0.1;
    pitchRef.current += (a[1] - pitchRef.current) * 0.1;
    draw(t);
    rafRef.current = requestAnimationFrame(frame);
  }

  function onPoint(e: PointerEvt): void {
    const field = fieldRef.current;
    if (!field) return;
    const r = field.getBoundingClientRect();
    pxRef.current = Math.min(1, Math.max(0, (e.clientX - r.left) / r.width));
    pyRef.current = Math.min(1, Math.max(0, (e.clientY - r.top) / r.height));
    if (!manualRef.current) manualRef.current = true;
    if (reduced()) {
      const a = aim();
      headingRef.current = a[0]; pitchRef.current = a[1];
      draw(STILL_T);
    }
  }

  function onLeave(): void {
    if (manualRef.current) { pxRef.current = 0.5; pyRef.current = 0.5; }
  }

  function onKeyDown(e: KeyEvt): void {
    const deltas: Record<string, [number, number]> = {
      ArrowLeft: [-0.07, 0], ArrowRight: [0.07, 0], ArrowUp: [0, -0.06], ArrowDown: [0, 0.06],
    };
    const d = deltas[e.key];
    if (!d) return;
    e.preventDefault();
    if (!manualRef.current) manualRef.current = true;
    pxRef.current = Math.max(0, Math.min(1, pxRef.current + d[0]));
    pyRef.current = Math.max(0, Math.min(1, pyRef.current + d[1]));
    if (reduced()) {
      const a = aim();
      headingRef.current = a[0]; pitchRef.current = a[1];
      draw(STILL_T);
    }
  }

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    rtRef.current = renderWidth;
    colRef.current = {
      wallA: tokRGB(root, "--br-wallA"),
      wallB: tokRGB(root, "--br-wallB"),
      floor: tokRGB(root, "--br-floor"),
      ceil: tokRGB(root, "--br-ceil"),
      shade: tokRGB(root, "--br-shade"),
    };
    fit();
    function onResize(): void {
      fit();
      if (reduced()) draw(STILL_T);
    }
    window.addEventListener("resize", onResize);
    if (reduced()) {
      // reduce — 코너가 읽히는 각도의 한 장만
      headingRef.current = 0.78; pitchRef.current = 0.1;
      draw(STILL_T);
      setStill(true);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [renderWidth]);

  const rootCls = still ? `${styles.root} ${styles.isStill}` : styles.root;

  return (
    <main className={styles.stage}>
      <div className={rootCls} ref={rootRef} style={vars}>
        <p className={styles.hint}>
          <svg className={styles.ico} viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M228.92 49.69a8 8 0 0 0-6.86-3.69H136a8 8 0 0 0 0 16h67.89l-83.6 95.47l-45-39.06a8 8 0 0 0-11.19.77l-56 64a8 8 0 1 0 11.9 10.62l50.59-57.87l45.11 39.15a8 8 0 0 0 11-.42l96-109.63a8 8 0 0 0 1.19-8.37Z" opacity=".2"/><path d="M224 104a8 8 0 0 0-8 8v78H40V40h136a8 8 0 0 0 0-16H40a16 16 0 0 0-16 16v152a16 16 0 0 0 16 16h176a16 16 0 0 0 16-16v-80a8 8 0 0 0-8-8m-24-72a24 24 0 1 0 24 24a24 24 0 0 0-24-24m0 32a8 8 0 1 1 8-8a8 8 0 0 1-8 8"/></g></svg>
          <span>카메라가 방 안에 들어가 있습니다 — 법선이 바라보는 방향으로 벽 색이 나뉩니다</span>
        </p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onPointerMove={onPoint}
          onPointerLeave={onLeave}
          onKeyDown={onKeyDown}
        >
          <canvas className={styles.cv} ref={cvRef}></canvas>
        </div>
        <div className={styles.bar}>
          <span className={styles.meta}><b className={styles.val}>{res}</b> 렌더 타깃 · 스텝 56</span>
          <span className={styles.metaDim}>모서리 둥글기 r=0.5</span>
        </div>
      </div>
    </main>
  );
}