05三角片ごとの落下を計算する破片トランジション

<main class="stage">
<div class="rv is-demo" id="rv">
  <p class="rv__hint"><span>クリックまたはEnterキーを押すと、三角の破片が距離順に砕けて落ち下の場面が現れます</span></p>
  <div class="rv__panel" id="panel" tabindex="0" role="button" aria-label="三角の破片ごとに落下を計算するフラグメント転換をもう一度再生">
    <canvas class="rv__cv" id="cv" aria-hidden="true"></canvas>
  </div>
</div>
</main>

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

// 계산 겹(리빌 판정)은 index.html 의 PRECOMPUTE()/RENDER() 에 있다. 여기는 무대·레이아웃만.
$duration: $dur-loop;
$easing:   $ease-out;
$color:    $subject-mint;

@include stage($stage-ink);

.rv {
  --img-a1: #{$stage-orange};
  --img-a2: #{$subject-cream};
  --img-b1: #{$subject-blue};
  --img-b2: #{$subject-sky};
  --accent: #{$color};
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  width: min(400px, 92vw);
}

.rv__hint {
  margin: 0;
  color: rgba($subject-cream, .78);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.35;
  text-align: center;
}

.rv__panel {
  position: relative;
  width: 100%;
  height: 176px;
  border-radius: $r-card;
  overflow: hidden;
  cursor: pointer;
  box-shadow: 0 0 0 1px rgba($subject-cream, .14);
  transition: box-shadow $duration $easing;
}

.rv__panel:hover {
  box-shadow: 0 0 0 1px $color;
}

.rv__panel:focus-visible {
  outline: 2px solid $color;
  outline-offset: 2px;
}

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

@media (max-width: 340px) {
  .rv__hint { font-size: 11px; }
  .rv__panel, .rv__cv { height: 120px; }
}

@media (prefers-reduced-motion: reduce) {
  .rv__panel { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.rv {
  --img-a1: #ff4d1f;
  --img-a2: #fff7e6;
  --img-b1: #2f6df6;
  --img-b2: #6ec8ff;
  --accent: #4cd4a6;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  width: min(400px, 92vw);
}

.rv__hint {
  margin: 0;
  color: rgba(255, 247, 230, 0.78);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.35;
  text-align: center;
}

.rv__panel {
  position: relative;
  width: 100%;
  height: 176px;
  border-radius: 16px;
  overflow: hidden;
  cursor: pointer;
  box-shadow: 0 0 0 1px rgba(255, 247, 230, 0.14);
  transition: box-shadow 2s ease-out;
}

.rv__panel:hover {
  box-shadow: 0 0 0 1px #4cd4a6;
}

.rv__panel:focus-visible {
  outline: 2px solid #4cd4a6;
  outline-offset: 2px;
}

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

@media (max-width: 340px) {
  .rv__hint {
    font-size: 11px;
  }
  .rv__panel, .rv__cv {
    height: 120px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rv__panel {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('rv');
  var panel = document.getElementById('panel');
  var cv = document.getElementById('cv');
  var ctx = cv.getContext('2d');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var isDemo = true;

  // 결정론 난수 — 이 데모는 Math.random 을 쓰지 않는다. LCG(선형합동생성기) 하나로 장면을 만든다.
  function makeLcg(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }

  var css = getComputedStyle(root);
  function tok(name, fb) { var v = css.getPropertyValue(name); return v ? (v.trim() || fb) : fb; }
  var COLOR_A1 = tok('--img-a1', '#ff5a2e');
  var COLOR_A2 = tok('--img-a2', '#fff3e6');
  var COLOR_B1 = tok('--img-b1', '#2e6bff');
  var COLOR_B2 = tok('--img-b2', '#bfe4ff');

  var W = 0, H = 0, dpr = 1;
  var bufA = document.createElement('canvas');
  var bufB = document.createElement('canvas');
  var bctxA = bufA.getContext('2d');
  var bctxB = bufB.getContext('2d');

  // 장면 A(따뜻한 톤)·B(차가운 톤) — 전부 캔버스로 직접 그린다. 외부 사진·파일 0.
  function paintScene(bctx, w, h, seed, warm) {
    var rng = makeLcg(seed);
    var g = bctx.createLinearGradient(0, 0, w, h);
    if (warm) { g.addColorStop(0, COLOR_A1); g.addColorStop(1, COLOR_A2); }
    else { g.addColorStop(0, COLOR_B1); g.addColorStop(1, COLOR_B2); }
    bctx.fillStyle = g;
    bctx.fillRect(0, 0, w, h);
    bctx.globalAlpha = 0.55;
    if (warm) {
      for (var i = 0; i < 8; i++) {
        bctx.fillStyle = i % 2 ? COLOR_A2 : COLOR_A1;
        bctx.beginPath();
        bctx.arc(rng() * w, rng() * h, 12 + rng() * 30, 0, Math.PI * 2);
        bctx.fill();
      }
    } else {
      var bandW = Math.max(14, w * 0.05);
      for (var x = -h; x < w + h; x += bandW * 2) {
        bctx.fillStyle = COLOR_B2;
        bctx.beginPath();
        bctx.moveTo(x, 0); bctx.lineTo(x + bandW, 0); bctx.lineTo(x + bandW - h, h); bctx.lineTo(x - h, h);
        bctx.closePath(); bctx.fill();
      }
      for (var j = 0; j < 6; j++) {
        bctx.fillStyle = COLOR_A2;
        bctx.beginPath(); bctx.arc(rng() * w, rng() * h, 5 + rng() * 9, 0, Math.PI * 2); bctx.fill();
      }
    }
    bctx.globalAlpha = 1;
  }

  var SEED_A = 501, SEED_B = 502;
  var PLAY_MS = 1100;
  var SHARD_PX = 30; // 조각 크기 — 변형: 30px -> 46px(더 굵은 파편)
  var FALL_WINDOW = 0.22;
  var FALL_DIST_PX = 60;
  var shards;

  function PRECOMPUTE() {
    var cols = Math.ceil(W / SHARD_PX), rows = Math.ceil(H / SHARD_PX);
    var maxDist = Math.hypot(W, H);
    shards = [];
    for (var r = 0; r < rows; r++) {
      for (var c = 0; c < cols; c++) {
        var x0 = c * SHARD_PX, y0 = r * SHARD_PX, x1 = x0 + SHARD_PX, y1 = y0 + SHARD_PX;
        var tris = [[[x0, y0], [x1, y0], [x0, y1]], [[x1, y0], [x1, y1], [x0, y1]]];
        for (var i = 0; i < tris.length; i++) {
          var tri = tris[i];
          var cx = (tri[0][0] + tri[1][0] + tri[2][0]) / 3;
          var cy = (tri[0][1] + tri[1][1] + tri[2][1]) / 3;
          shards.push({ tri: tri, dist: Math.hypot(cx, cy) / maxDist });
        }
      }
    }
  }

  function clipTri(tri) {
    ctx.beginPath();
    ctx.moveTo(tri[0][0], tri[0][1]);
    ctx.lineTo(tri[1][0], tri[1][1]);
    ctx.lineTo(tri[2][0], tri[2][1]);
    ctx.closePath();
    ctx.clip();
  }

  function RENDER(p) {
    ctx.drawImage(bufB, 0, 0, W, H);
    for (var i = 0; i < shards.length; i++) {
      var s = shards[i];
      if (s.dist > p) {
        ctx.save(); clipTri(s.tri);
        ctx.drawImage(bufA, 0, 0, cv.width, cv.height, 0, 0, W, H);
        ctx.restore();
      } else {
        var u = Math.min(1, (p - s.dist) / FALL_WINDOW);
        if (u < 1) {
          var off = u * u * FALL_DIST_PX;
          ctx.save();
          ctx.globalAlpha = 1 - u;
          ctx.translate(0, off);
          clipTri(s.tri);
          ctx.drawImage(bufA, 0, 0, cv.width, cv.height, 0, -off, W, H);
          ctx.restore();
        }
      }
    }
  }

  function fit() {
    var r = panel.getBoundingClientRect();
    dpr = window.devicePixelRatio || 1;
    W = r.width; H = r.height;
    cv.width = Math.round(W * dpr); cv.height = Math.round(H * dpr);
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    bufA.width = bufB.width = cv.width;
    bufA.height = bufB.height = cv.height;
    bctxA.setTransform(dpr, 0, 0, dpr, 0, 0);
    bctxB.setTransform(dpr, 0, 0, dpr, 0, 0);
    paintScene(bctxA, W, H, SEED_A, true);
    paintScene(bctxB, W, H, SEED_B, false);
    PRECOMPUTE();
  }

  function human() { if (isDemo) { root.classList.remove('is-demo'); isDemo = false; } }

  var progress = 0, target = 0, playT0 = 0, playFrom = 0, playing = false;

  function easeInOut(t) { return t < 0.5 ? 2 * t * t : 1 - Math.pow(-2 * t + 2, 2) / 2; }

  function play() {
    // 실사용 경로 — 클릭·Enter·Space 로 두 장면을 다시 전환한다.
    human();
    playFrom = progress; target = progress < 0.5 ? 1 : 0;
    playT0 = 0; playing = true;
  }

  function stepPlay(now) {
    if (!playing) return;
    if (!playT0) playT0 = now;
    var t = Math.min(1, (now - playT0) / PLAY_MS);
    progress = playFrom + (target - playFrom) * easeInOut(t);
    if (t >= 1) { playing = false; progress = target; }
  }

  var DRIVE_PERIOD_MS = 2000; // 렌더 캐처 창(설정 초=2.0)과 같은 주기 — 시연 전용
  var driveStart = 0;
  function triangle(frac) { return frac < 0.5 ? frac * 2 : 2 - frac * 2; }
  function driveTick(now) {
    if (!driveStart) driveStart = now;
    if (isDemo) { // .is-demo && !reduce 경로에서만 실행된다(아래 reduce 분기)
      var frac = ((now - driveStart) % DRIVE_PERIOD_MS) / DRIVE_PERIOD_MS;
      progress = triangle(frac);
    }
    requestAnimationFrame(driveTick);
  }

  function frame(now) {
    stepPlay(now);
    RENDER(progress);
    requestAnimationFrame(frame);
  }

  window.addEventListener('resize', fit);
  fit();

  if (reduce) {
    // reduce — 자동 루프 없음, 계산은 그대로 둘고 즉시 전환만 허용한다.
    root.classList.add('is-still');
    progress = 0.5; RENDER(progress);
    panel.addEventListener('click', function () { human(); progress = progress < 0.5 ? 1 : 0; RENDER(progress); });
    panel.addEventListener('keydown', function (e) {
      if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); human(); progress = progress < 0.5 ? 1 : 0; RENDER(progress); }
    });
  } else {
    panel.addEventListener('click', play);
    panel.addEventListener('keydown', function (e) {
      if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); play(); }
    });
    requestAnimationFrame(frame);
    requestAnimationFrame(driveTick);
  }
})();

import { useEffect, useRef } from "react";
import styles from "./ShardFractureFall.module.scss";

type Shard = { tri: number[][]; dist: number };

export default function ShardFractureFall() {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const panelRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    const panel = panelRef.current;
    const cv = cvRef.current;
    if (!root || !panel || !cv) return;
    const ctx = cv.getContext("2d");
    if (!ctx) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let isDemo = true;

    // 결정론 난수 — 이 데모는 Math.random 을 쓰지 않는다. LCG(선형합동생성기) 하나로 장면을 만든다.
    function makeLcg(seed: number) {
      let s = seed >>> 0;
      return function () {
        s = (s * 1664525 + 1013904223) >>> 0;
        return s / 4294967296;
      };
    }

    const css = getComputedStyle(root);
    function tok(name: string, fb: string) {
      const v = css.getPropertyValue(name);
      return v ? v.trim() || fb : fb;
    }
    const COLOR_A1 = tok("--img-a1", "#ff5a2e");
    const COLOR_A2 = tok("--img-a2", "#fff3e6");
    const COLOR_B1 = tok("--img-b1", "#2e6bff");
    const COLOR_B2 = tok("--img-b2", "#bfe4ff");

    let W = 0;
    let H = 0;
    let dpr = 1;
    const bufA = document.createElement("canvas");
    const bufB = document.createElement("canvas");
    const bctxA = bufA.getContext("2d");
    const bctxB = bufB.getContext("2d");
    if (!bctxA || !bctxB) return;

    // 장면 A(따뜻한 톤)·B(차가운 톤) — 전부 캔버스로 직접 그린다. 외부 사진·파일 0.
    function paintScene(bctx: CanvasRenderingContext2D, w: number, h: number, seed: number, warm: boolean) {
      const rng = makeLcg(seed);
      const g = bctx.createLinearGradient(0, 0, w, h);
      if (warm) {
        g.addColorStop(0, COLOR_A1);
        g.addColorStop(1, COLOR_A2);
      } else {
        g.addColorStop(0, COLOR_B1);
        g.addColorStop(1, COLOR_B2);
      }
      bctx.fillStyle = g;
      bctx.fillRect(0, 0, w, h);
      bctx.globalAlpha = 0.55;
      if (warm) {
        for (let i = 0; i < 8; i++) {
          bctx.fillStyle = i % 2 ? COLOR_A2 : COLOR_A1;
          bctx.beginPath();
          bctx.arc(rng() * w, rng() * h, 12 + rng() * 30, 0, Math.PI * 2);
          bctx.fill();
        }
      } else {
        const bandW = Math.max(14, w * 0.05);
        for (let x = -h; x < w + h; x += bandW * 2) {
          bctx.fillStyle = COLOR_B2;
          bctx.beginPath();
          bctx.moveTo(x, 0);
          bctx.lineTo(x + bandW, 0);
          bctx.lineTo(x + bandW - h, h);
          bctx.lineTo(x - h, h);
          bctx.closePath();
          bctx.fill();
        }
        for (let j = 0; j < 6; j++) {
          bctx.fillStyle = COLOR_A2;
          bctx.beginPath();
          bctx.arc(rng() * w, rng() * h, 5 + rng() * 9, 0, Math.PI * 2);
          bctx.fill();
        }
      }
      bctx.globalAlpha = 1;
    }

    const SEED_A = 501;
    const SEED_B = 502;
    const PLAY_MS = 1100;
    const SHARD_PX = 30; // 조각 크기 — 변형: 30px -> 46px(더 굵은 파편)
    const FALL_WINDOW = 0.22;
    const FALL_DIST_PX = 60;
    let shards: Shard[] = [];

    function PRECOMPUTE() {
      const cols = Math.ceil(W / SHARD_PX);
      const rows = Math.ceil(H / SHARD_PX);
      const maxDist = Math.hypot(W, H);
      shards = [];
      for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
          const x0 = c * SHARD_PX;
          const y0 = r * SHARD_PX;
          const x1 = x0 + SHARD_PX;
          const y1 = y0 + SHARD_PX;
          const tris: number[][][] = [
            [[x0, y0], [x1, y0], [x0, y1]],
            [[x1, y0], [x1, y1], [x0, y1]],
          ];
          for (let i = 0; i < tris.length; i++) {
            const tri = tris[i];
            const cx = (tri[0][0] + tri[1][0] + tri[2][0]) / 3;
            const cy = (tri[0][1] + tri[1][1] + tri[2][1]) / 3;
            shards.push({ tri, dist: Math.hypot(cx, cy) / maxDist });
          }
        }
      }
    }

    function clipTri(tri: number[][]) {
      ctx!.beginPath();
      ctx!.moveTo(tri[0][0], tri[0][1]);
      ctx!.lineTo(tri[1][0], tri[1][1]);
      ctx!.lineTo(tri[2][0], tri[2][1]);
      ctx!.closePath();
      ctx!.clip();
    }

    function RENDER(p: number) {
      ctx!.drawImage(bufB, 0, 0, W, H);
      for (let i = 0; i < shards.length; i++) {
        const s = shards[i];
        if (s.dist > p) {
          ctx!.save();
          clipTri(s.tri);
          ctx!.drawImage(bufA, 0, 0, cv!.width, cv!.height, 0, 0, W, H);
          ctx!.restore();
        } else {
          const u = Math.min(1, (p - s.dist) / FALL_WINDOW);
          if (u < 1) {
            const off = u * u * FALL_DIST_PX;
            ctx!.save();
            ctx!.globalAlpha = 1 - u;
            ctx!.translate(0, off);
            clipTri(s.tri);
            ctx!.drawImage(bufA, 0, 0, cv!.width, cv!.height, 0, -off, W, H);
            ctx!.restore();
          }
        }
      }
    }

    function fit() {
      const r = panel!.getBoundingClientRect();
      dpr = window.devicePixelRatio || 1;
      W = r.width;
      H = r.height;
      cv!.width = Math.round(W * dpr);
      cv!.height = Math.round(H * dpr);
      ctx!.setTransform(dpr, 0, 0, dpr, 0, 0);
      bufA.width = bufB.width = cv!.width;
      bufA.height = bufB.height = cv!.height;
      bctxA!.setTransform(dpr, 0, 0, dpr, 0, 0);
      bctxB!.setTransform(dpr, 0, 0, dpr, 0, 0);
      paintScene(bctxA!, W, H, SEED_A, true);
      paintScene(bctxB!, W, H, SEED_B, false);
      PRECOMPUTE();
    }

    function human() {
      if (isDemo) {
        root!.classList.remove("is-demo");
        isDemo = false;
      }
    }

    let progress = 0;
    let target = 0;
    let playT0 = 0;
    let playFrom = 0;
    let playing = false;

    function easeInOut(t: number) {
      return t < 0.5 ? 2 * t * t : 1 - Math.pow(-2 * t + 2, 2) / 2;
    }

    function play() {
      // 실사용 경로 — 클릭·Enter·Space 로 두 장면을 다시 전환한다.
      human();
      playFrom = progress;
      target = progress < 0.5 ? 1 : 0;
      playT0 = 0;
      playing = true;
    }

    function stepPlay(now: number) {
      if (!playing) return;
      if (!playT0) playT0 = now;
      const t = Math.min(1, (now - playT0) / PLAY_MS);
      progress = playFrom + (target - playFrom) * easeInOut(t);
      if (t >= 1) {
        playing = false;
        progress = target;
      }
    }

    const DRIVE_PERIOD_MS = 2000; // 렌더 캐처 창(설정 초=2.0)과 같은 주기 — 시연 전용
    let driveStart = 0;
    let rafFrame = 0;
    let rafDrive = 0;

    function triangle(frac: number) {
      return frac < 0.5 ? frac * 2 : 2 - frac * 2;
    }

    function driveTick(now: number) {
      if (!driveStart) driveStart = now;
      if (isDemo) {
        // .is-demo && !reduce 경로에서만 실행된다(아래 reduce 분기)
        const frac = ((now - driveStart) % DRIVE_PERIOD_MS) / DRIVE_PERIOD_MS;
        progress = triangle(frac);
      }
      rafDrive = requestAnimationFrame(driveTick);
    }

    function frame(now: number) {
      stepPlay(now);
      RENDER(progress);
      rafFrame = requestAnimationFrame(frame);
    }

    function onClick() {
      play();
    }
    function onKeyDown(e: Event) {
      const ke = e as KeyboardEvent;
      if (ke.key === "Enter" || ke.key === " ") {
        ke.preventDefault();
        play();
      }
    }
    function onClickReduce() {
      human();
      progress = progress < 0.5 ? 1 : 0;
      RENDER(progress);
    }
    function onKeyDownReduce(e: Event) {
      const ke = e as KeyboardEvent;
      if (ke.key === "Enter" || ke.key === " ") {
        ke.preventDefault();
        human();
        progress = progress < 0.5 ? 1 : 0;
        RENDER(progress);
      }
    }

    window.addEventListener("resize", fit);
    fit();

    if (reduce) {
      // reduce — 자동 루프 없음, 계산은 그대로 두고 즉시 전환만 허용한다.
      root.classList.add("is-still");
      progress = 0.5;
      RENDER(progress);
      panel.addEventListener("click", onClickReduce);
      panel.addEventListener("keydown", onKeyDownReduce);
    } else {
      panel.addEventListener("click", onClick);
      panel.addEventListener("keydown", onKeyDown);
      rafFrame = requestAnimationFrame(frame);
      rafDrive = requestAnimationFrame(driveTick);
    }

    return () => {
      window.removeEventListener("resize", fit);
      cancelAnimationFrame(rafFrame);
      cancelAnimationFrame(rafDrive);
      if (reduce) {
        panel.removeEventListener("click", onClickReduce);
        panel.removeEventListener("keydown", onKeyDownReduce);
      } else {
        panel.removeEventListener("click", onClick);
        panel.removeEventListener("keydown", onKeyDown);
      }
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.root} is-demo`} ref={rootRef}>
        <p className={styles.hint}>
          <span>클릭하거나 Enter 를 누르면 삼각 조각이 거리 순으로 부서져 떨어지며 아래 장면이 드러납니다</span>
        </p>
        <div
          className={styles.panel}
          ref={panelRef}
          tabIndex={0}
          role="button"
          aria-label="삼각 조각마다 낙하를 계산하는 파편 전환 다시 재생"
        >
          <canvas className={styles.cv} ref={cvRef} aria-hidden="true" />
        </div>
      </div>
    </main>
  );
}