05Scroll landscape — mountain ranges unveiling as you roll

<main class="stage">
<div class="me is-demo" id="meRoot">
  <p class="me__hint">
    <span>Scroll landscape</span>
    <span class="me__desc">Bind scroll to travel through terrain and ranges and valleys stream past the noise</span>
  </p>
  <div class="me__field" role="application" aria-label="Scroll landscape explorer" tabindex="0">
    <canvas class="me__cv" id="meCv"></canvas>
  </div>
  <div class="me__bar">
    <span class="me__meta">wheel or drag to travel · moving ramp 3 octaves · depth 12px</span>
    <span class="me__meta me__meta--dim">ImageData · travel offset</span>
  </div>
</div>
</main>

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

// 스크롤 지형(05) — keyframes 없음. 여행 오프셋이 깊이 샘플을 흐르게 한다.
// 무대 잉크 — 심야 탐사판 톤.

$me-stage: #191c22;
@include stage($me-stage);

$me-panel: #232830;   // 탐사판 바닥 — 무대보다 한 단계 밝은 밤청
$me-text:  #d3dae6;   // 라벨 글자 — 밝은 청회
$me-p0:    #ccd8ea;   // 노이즈 파스텔 1 — 얼음 블루
$me-p1:    #e2d8ea;   // 노이즈 파스텔 2 — 라일락
$me-p2:    #d6e4da;   // 노이즈 파스텔 3 — 민트 크림
$me-p3:    #eae0cc;   // 노이즈 파스텔 4 — 크림
$me-p4:    #51586a;   // 노이즈 어두운 칸 — 저채소 청회

$duration: $dur-loop;
$easing: $ease-out;
$color: $me-p0;

.me {
  --me-p0: #{$me-p0};
  --me-p1: #{$me-p1};
  --me-p2: #{$me-p2};
  --me-p3: #{$me-p3};
  --me-p4: #{$me-p4};

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

.me__hint {
  display: flex; flex-direction: column; gap: 0; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: $me-text;
}
.me__desc {
  margin-top: $sp-1;
  font-weight: 500; font-size: clamp(9px, 2.4vw, 10px); line-height: 1.4;
  color: rgba($me-text, .78);
}

.me__field {
  position: relative; height: 180px;
  border-radius: $r-card; overflow: hidden;
  background: $me-panel;
  box-shadow: inset 0 0 0 1px rgba($me-text, .16);
  cursor: grab;
  touch-action: none;
}
.me__field:active { cursor: grabbing; }
.me__field:focus-visible { outline: 2px solid $me-p0; outline-offset: 2px; }

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

.me__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.me__meta { font-size: 10px; font-weight: 500; color: rgba($me-text, .78); }

@media (max-width: 340px) {
  .me { gap: $sp-1; }
  .me__field { height: 100px; }
  .me__meta--dim { display: none; }
}

// reduce — 골짜기 한 장만 남는다.
@media (prefers-reduced-motion: reduce) {
  .me.is-still .me__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: #191c22;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.me {
  --me-p0: #ccd8ea;
  --me-p1: #e2d8ea;
  --me-p2: #d6e4da;
  --me-p3: #eae0cc;
  --me-p4: #51586a;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.me__hint {
  display: flex;
  flex-direction: column;
  gap: 0;
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: #d3dae6;
}

.me__desc {
  margin-top: 4px;
  font-weight: 500;
  font-size: clamp(9px, 2.4vw, 10px);
  line-height: 1.4;
  color: rgba(211, 218, 230, 0.78);
}

.me__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #232830;
  box-shadow: inset 0 0 0 1px rgba(211, 218, 230, 0.16);
  cursor: grab;
  touch-action: none;
}

.me__field:active {
  cursor: grabbing;
}

.me__field:focus-visible {
  outline: 2px solid #ccd8ea;
  outline-offset: 2px;
}

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

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

.me__meta {
  font-size: 10px;
  font-weight: 500;
  color: rgba(211, 218, 230, 0.78);
}

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

// Scroll landscape(05) — 깊이 지도를 가로지르는 이동 거리를 입력에 묶는다.
// 지형 높이 = 무빙 램프 3옥타브(서로 다른 파장의 사인 합) — x 에 여행 오프셋을 더해 샘플한다.
// 휠·가로 드래그로 직접 여행하고, 손을 떼면 자동 주행이 이어받아 루프가 끊기지 않는다.
// 산맥이 노이즈 너머로 흐르는 대표 장면 — 스크롤 트리거와 픽셀 계산이 한 몸이다.
(function () {
  // ── 변형 상수 블록 ──
  var MAXSHIFT = 12;   // 산 높이(px)
  var SPEED = 90;      // 자동 주행 속도(px/초)
  // ─────────────────

  var root = document.getElementById('meRoot');
  var cvEl = document.getElementById('meCv');
  if (!root || !cvEl) return;
  var fieldEl = cvEl.parentElement;

  var css = getComputedStyle(root);
  function tokRGB(name) {
    var s = css.getPropertyValue(name).trim();
    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 PAL = [];
  for (var i = 0; i < 5; i++) PAL.push(tokRGB('--me-p' + i));

  function baseIdx(x, y) {
    var h = (Math.imul(x + 11, 374761393) + Math.imul(y + 7, 668265263)) >>> 0;
    h ^= h >>> 13;
    h = Math.imul(h, 1274126177) >>> 0;
    h ^= h >>> 16;
    return ((h % PAL.length) + PAL.length) % PAL.length;
  }

  var ctx = cvEl.getContext('2d');
  var W = 0, H = 0, img = null;

  function fit() {
    var r = fieldEl.getBoundingClientRect();
    W = Math.round(r.width); H = Math.round(r.height);
    cvEl.width = W; cvEl.height = H;
    img = ctx.createImageData(W, H);
  }

  // 지형 — 3옥타브 무빙 램프. wx = 세계 좌표(여행 오프셋 더한 x)
  function terrain(wx, y) {
    var v = 0;
    v += Math.sin(wx * 0.011 + y * 0.004) * 0.45;
    v += Math.sin(wx * 0.031 + 1.7 + y * 0.010) * 0.30;
    v += Math.sin(wx * 0.074 + 4.2) * 0.18;
    v += (Math.cos(wx * 0.005 + y * 0.006) * 0.5 + 0.5) * 0.35;
    var front = y / H;                       // 화면 하단(앞쪽)이 더 높게 솟는다
    var h01 = Math.max(0, Math.min(1, v * 0.5 + 0.5)) * (0.35 + 0.65 * front * front);
    return h01;
  }

  function draw(travel, hover) {
    var d = img.data, x, y, di;
    var col = new Int32Array(W);
    for (y = 0; y < H; y++) {
      for (x = 0; x < W; x++) {
        var s = Math.round(terrain(x + travel, y) * MAXSHIFT);
        if (s <= 0) {
          col[x] = baseIdx(x, y);
        } else {
          var from = x - s;
          col[x] = from >= 0 ? col[from] : baseIdx(from + W, y);
        }
      }
      for (x = 0; x < W; x++) {
        var c = PAL[col[x]];
        di = (y * W + x) * 4;
        d[di] = c[0]; d[di + 1] = c[1]; d[di + 2] = c[2]; d[di + 3] = 255;
      }
    }
    ctx.putImageData(img, 0, 0);

    if (!hover) {
      ctx.fillStyle = 'rgba(214, 222, 236, 0.8)';
      ctx.font = '500 11px "Segoe UI", sans-serif';
      ctx.textAlign = 'center';
      ctx.fillText('Wheel or drag to travel the terrain', W / 2, H - 10);
    }
  }

  // ── 입력 — 휠 · 가로 드래그 ──
  var travel = 0, hover = false, dragX = null;
  fieldEl.addEventListener('wheel', function (ev) {
    ev.preventDefault();
    travel += (ev.deltaY + ev.deltaX) * 0.6;
    hover = true;
  }, { passive: false });
  fieldEl.addEventListener('pointerdown', function (ev) {
    dragX = ev.clientX; hover = true;
    ev.preventDefault();
  });
  window.addEventListener('pointermove', function (ev) {
    if (dragX === null) return;
    travel -= (ev.clientX - dragX) * 1.2;
    dragX = ev.clientX;
  });
  window.addEventListener('pointerup', function () { dragX = null; });
  fieldEl.addEventListener('pointerenter', function () { hover = true; });

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var t0 = -1, lastNow = -1;
  function frame(now) {
    if (t0 < 0) { t0 = now; lastNow = now; }
    var dt = Math.min(0.05, (now - lastNow) / 1000 || 0.016);
    lastNow = now;
    travel += dt * SPEED;   // 자동 주행 — 손이 있으면 휠·드래그가 겹쳐 더해진다
    draw(travel, hover);
    requestAnimationFrame(frame);
  }
  window.addEventListener('resize', function () {
    fit();
    if (reduce) draw(0, true);
  });
  fit();
  if (reduce) {
    draw(0, true);   // reduce — 골짜기 한 장만 고정
    root.classList.add('is-still');
  } else {
    requestAnimationFrame(frame);
  }
})();

// MagicEyeScrollLandscapeReveal — vanilla 판(run/325/demo/05-magic-eye-scroll-landscape-reveal/index.html) 의 React 포트.
// 깊이 지도를 가로지르는 이동 거리를 입력에 묶는다. 지형 높이 = 무빙 램프 3옥타브
// (서로 다른 파장의 사인 합) — x 에 여행 오프셋을 더해 샘플한다.
// 휠·가로 드래그로 직접 여행하고, 손을 떼면 자동 주행이 이어받아 루프가 끊기지 않는다.
// 산맥이 노이즈 너머로 흐르는 대표 장면 — 스크롤 트리거와 픽셀 계산이 한 몸이다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./MagicEyeScrollLandscapeReveal.module.scss";

export type MagicEyeScrollLandscapeRevealProps = {
  duration?: string;
  easing?: string;
  color?: string;
  maxshift?: number;  // 산 높이(px)
  speed?: number;     // 자동 주행 속도(px/초)
};

// ── 변형 상수(기본값) — vanilla 판과 동일 ──
const MAXSHIFT = 12;   // 산 높이(px)
const SPEED    = 90;   // 자동 주행 속도(px/초)

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type RGB = [number, number, number];

const FIELD_LABEL = "스크롤 지형 탐사판";
const META_LEFT = "휠·드래그로 이동 · 무빙 램프 3옥타브 · 깊이 12px";
const META_RIGHT = "ImageData · 이동 오프셋";
const HINT_TITLE = "스크롤 지형";
const HINT_DESC = "스크롤 위치를 지형 이동 거리에 묶으면 산맥과 골짜기가 노이즈 너머로 흐릅니다";
const GUIDE = "휠이나 드래그로 지형을 지나가 보세요";

export default function MagicEyeScrollLandscapeReveal({
  duration = "2s",
  easing = "ease-out",
  color = "#ccd8ea",
  maxshift = MAXSHIFT,
  speed = SPEED
}: MagicEyeScrollLandscapeRevealProps) {
  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 palRef = useRef<RGB[] | null>(null);
  const imgRef = useRef<ImageData | null>(null);
  const travelRef = useRef(0) as Box<number>;
  const hoverRef = useRef(false) as Box<boolean>;
  const dragRef = useRef<number | null>(null) as Box<number | null>;
  const wRef = useRef(0) as Box<number>;
  const hRef = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  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();
    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)];
  }

  function baseIdx(x: number, y: number): number {
    const pal = palRef.current;
    if (!pal) return 0;
    let h = (Math.imul(x + 11, 374761393) + Math.imul(y + 7, 668265263)) >>> 0;
    h ^= h >>> 13;
    h = Math.imul(h, 1274126177) >>> 0;
    h ^= h >>> 16;
    return ((h % pal.length) + pal.length) % pal.length;
  }

  function fit(): void {
    const field = fieldRef.current;
    const cv = cvRef.current;
    const ctx = ctxRef.current;
    if (!field || !cv || !ctx) return;
    const r = field.getBoundingClientRect();
    wRef.current = Math.round(r.width);
    hRef.current = Math.round(r.height);
    cv.width = wRef.current;
    cv.height = hRef.current;
    imgRef.current = ctx.createImageData(wRef.current, hRef.current);
  }

  // 지형 — 3옥타브 무빙 램프. wx = 세계 좌표(여행 오프셋 더한 x)
  function terrain(wx: number, y: number): number {
    const H = hRef.current;
    let v = 0;
    v += Math.sin(wx * 0.011 + y * 0.004) * 0.45;
    v += Math.sin(wx * 0.031 + 1.7 + y * 0.010) * 0.30;
    v += Math.sin(wx * 0.074 + 4.2) * 0.18;
    v += (Math.cos(wx * 0.005 + y * 0.006) * 0.5 + 0.5) * 0.35;
    const front = y / H;                       // 화면 하단(앞쪽)이 더 높게 솟는다
    return Math.max(0, Math.min(1, v * 0.5 + 0.5)) * (0.35 + 0.65 * front * front);
  }

  function draw(travel: number, hover: boolean): void {
    const ctx = ctxRef.current;
    const img = imgRef.current;
    const pal = palRef.current;
    const W = wRef.current, H = hRef.current;
    if (!ctx || !img || !pal) return;
    const d = img.data;
    const col = new Int32Array(W);
    for (let y = 0; y < H; y++) {
      for (let x = 0; x < W; x++) {
        const s = Math.round(terrain(x + travel, y) * maxshift);
        if (s <= 0) {
          col[x] = baseIdx(x, y);
        } else {
          const from = x - s;
          col[x] = from >= 0 ? col[from] : baseIdx(from + W, y);
        }
      }
      for (let x = 0; x < W; x++) {
        const c = pal[col[x]];
        const di = (y * W + x) * 4;
        d[di] = c[0]; d[di + 1] = c[1]; d[di + 2] = c[2]; d[di + 3] = 255;
      }
    }
    ctx.putImageData(img, 0, 0);

    if (!hover) {
      ctx.fillStyle = "rgba(214, 222, 236, 0.8)";
      ctx.font = '500 11px "Segoe UI", sans-serif';
      ctx.textAlign = "center";
      ctx.fillText(GUIDE, W / 2, H - 10);
    }
  }

  let t0 = -1;
  let lastNow = -1;
  function frame(now: number): void {
    if (t0 < 0) { t0 = now; lastNow = now; }
    const dt = Math.min(0.05, (now - lastNow) / 1000 || 0.016);
    lastNow = now;
    travelRef.current += dt * speed;   // 자동 주행 — 손이 있으면 휠·드래그가 겹쳐 더해진다
    draw(travelRef.current, hoverRef.current);
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    const cv = cvRef.current;
    const field = fieldRef.current;
    if (!root || !cv || !field) return;
    const pal: RGB[] = [];
    for (let i = 0; i < 5; i++) pal.push(tokRGB(root, "--me-p" + i));
    palRef.current = pal;
    ctxRef.current = cv.getContext("2d");
    fit();

    // ── 입력 — 휠 · 가로 드래그 ──
    function onWheel(ev: WheelEvent): void {
      ev.preventDefault();
      travelRef.current += (ev.deltaY + ev.deltaX) * 0.6;
      hoverRef.current = true;
    }
    function onPointerDown(ev: PointerEvent): void {
      dragRef.current = ev.clientX; hoverRef.current = true;
      ev.preventDefault();
    }
    function onPointerMove(ev: PointerEvent): void {
      if (dragRef.current === null) return;
      travelRef.current -= (ev.clientX - dragRef.current) * 1.2;
      dragRef.current = ev.clientX;
    }
    function onPointerUp(): void { dragRef.current = null; }
    function onPointerEnter(): void { hoverRef.current = true; }

    field.addEventListener("wheel", onWheel, { passive: false });
    field.addEventListener("pointerdown", onPointerDown);
    window.addEventListener("pointermove", onPointerMove);
    window.addEventListener("pointerup", onPointerUp);
    field.addEventListener("pointerenter", onPointerEnter);

    function onResize(): void {
      fit();
      if (reduced()) draw(0, true);
    }
    window.addEventListener("resize", onResize);
    if (reduced()) {
      draw(0, true);                               // reduce — 골짜기 한 장만 고정
      setStill(true);
    } else {
      t0 = -1;
      lastNow = -1;
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      field.removeEventListener("wheel", onWheel);
      field.removeEventListener("pointerdown", onPointerDown);
      window.removeEventListener("pointermove", onPointerMove);
      window.removeEventListener("pointerup", onPointerUp);
      field.removeEventListener("pointerenter", onPointerEnter);
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [maxshift, speed]);

  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}>
          <span>{HINT_TITLE}</span>
          <span className={styles.desc}>{HINT_DESC}</span>
        </p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
        >
          <canvas className={styles.cv} ref={cvRef}></canvas>
        </div>
        <div className={styles.bar}>
          <span className={styles.meta}>{META_LEFT}</span>
          <span className={styles.metaDim}>{META_RIGHT}</span>
        </div>
      </div>
    </main>
  );
}