03Burst scatter — pieces scatter from the click point at differing angle values before fading

<main class="stage">
<div class="ctacfb is-demo" id="ctacfb">
  <div class="ctacfb__panel">
    <div class="ctacfb__wrap">
      <canvas class="ctacfb__canvas" id="ctacfbCanvas" width="220" height="120"></canvas>
      <button class="ctacfb__btn" id="ctacfbBtn" type="button">Complete purchase</button>
    </div>
    <span class="ctacfb__hint">Click to scatter pieces in every direction</span>
  </div>
</div>
</main>

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

// 계산 겹(중력·감쇠·회전)은 JS 캔버스에 있다 — 여기는 정적 배치만.
@include stage($stage-orange);

.stage { position: relative; }

.ctacfb__panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
  padding: $sp-5;
  border-radius: $r-card;
  background: $stage-paper;
}

.ctacfb__wrap {
  position: relative;
  width: 220px;
  height: 120px;
  display: grid;
  place-items: center;
}

.ctacfb__canvas {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.ctacfb__btn {
  position: relative;
  z-index: 1;
  border: 0;
  border-radius: $r-control;
  background: $subject-blue-deep;
  color: $subject-cream;
  font-family: inherit;
  font-weight: 700;
  font-size: 15px;
  padding: $sp-3 $sp-5;
  cursor: pointer;
}

.ctacfb__hint {
  color: rgba($subject-ink, .72);
  font-size: 12px;
  text-align: center;
}

@media (max-width: 340px) {
  .ctacfb__panel { padding: $sp-4; gap: $sp-2; }
  .ctacfb__wrap { width: 180px; height: 100px; }
  .ctacfb__btn { padding: $sp-2 $sp-4; font-size: 14px; }
}

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

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.stage {
  position: relative;
}

.ctacfb__panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 20px;
  border-radius: 16px;
  background: #ffffff;
}

.ctacfb__wrap {
  position: relative;
  width: 220px;
  height: 120px;
  display: grid;
  place-items: center;
}

.ctacfb__canvas {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.ctacfb__btn {
  position: relative;
  z-index: 1;
  border: 0;
  border-radius: 12px;
  background: #0a4fe8;
  color: #fff7e6;
  font-family: inherit;
  font-weight: 700;
  font-size: 15px;
  padding: 12px 20px;
  cursor: pointer;
}

.ctacfb__hint {
  color: rgba(23, 20, 26, 0.72);
  font-size: 12px;
  text-align: center;
}

@media (max-width: 340px) {
  .ctacfb__panel {
    padding: 16px;
    gap: 8px;
  }
  .ctacfb__wrap {
    width: 180px;
    height: 100px;
  }
  .ctacfb__btn {
    padding: 8px 16px;
    font-size: 14px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ctacfb__btn {
    transition: none !important;
  }
}

(function () {
  var root = document.getElementById('ctacfb');
  var btn = document.getElementById('ctacfbBtn');
  var canvas = document.getElementById('ctacfbCanvas');
  var ctx = canvas.getContext('2d');
  var COLORS = ['#5b8cf8', '#ff9ebb', '#4cd4a6', '#b9a0ff'];

  // 계산 겹: 조각마다 각도·속도 값을 난수로 부여하고, 매 프레임 중력(GRAVITY)을 속도에
  // 더하고 속도에 감쇠(DRAG)를 곱해 궤적을 계산한다. 회전 값도 각자 다른 속도로 누적하고
  // 투명도 값은 남은 수명 비율로 계산해 사라진다.
  var GRAVITY = 420, DRAG = 0.985, LIFE = 900;
  var particles = [];
  var raf = null, lastT = 0;

  function burst() {
    var cx = canvas.width / 2, cy = canvas.height * 0.35;
    particles = [];
    for (var i = 0; i < 18; i++) {
      var angle = (Math.PI * 2 * i) / 18 + (Math.random() - 0.5) * 0.5;
      var speed = 90 + Math.random() * 110;
      particles.push({
        x: cx, y: cy,
        vx: Math.cos(angle) * speed,
        vy: Math.sin(angle) * speed - 60,
        rot: Math.random() * Math.PI,
        vrot: (Math.random() - 0.5) * 10,
        color: COLORS[i % COLORS.length],
        age: 0
      });
    }
    if (!raf) { lastT = performance.now(); raf = requestAnimationFrame(tick); }
  }

  function tick(now) {
    var dt = Math.min((now - lastT) / 1000, 0.05);
    lastT = now;
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    var alive = false;
    for (var i = 0; i < particles.length; i++) {
      var p = particles[i];
      p.age += dt * 1000;
      if (p.age >= LIFE) { continue; }
      alive = true;
      p.vy += GRAVITY * dt;
      p.vx *= DRAG; p.vy *= DRAG;
      p.x += p.vx * dt; p.y += p.vy * dt;
      p.rot += p.vrot * dt;
      var op = Math.max(0, 1 - p.age / LIFE);
      ctx.save();
      ctx.globalAlpha = op;
      ctx.translate(p.x, p.y);
      ctx.rotate(p.rot);
      ctx.fillStyle = p.color;
      ctx.fillRect(-4, -3, 8, 6);
      ctx.restore();
    }
    if (alive) {
      raf = requestAnimationFrame(tick);
    } else {
      raf = null;
    }
  }

  function wireReal() {
    btn.addEventListener('click', function () { root.classList.remove('is-demo'); stopAutoplay(); burst(); });
  }
  wireReal();

  var autoplayTimer = null;
  function stopAutoplay() { if (autoplayTimer) { clearInterval(autoplayTimer); autoplayTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoplayTimer = setInterval(burst, 1100); }
})();

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

type Particle = {
  x: number; y: number; vx: number; vy: number;
  rot: number; vrot: number; color: string; age: number;
};

export type CtaBtnConfettiBurstProps = {
  color?: string;
};

export default function CtaBtnConfettiBurst({
  color = "#0a4fe8",
}: CtaBtnConfettiBurstProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const btn = root.querySelector<HTMLButtonElement>(`.${styles.btn}`);
    const canvas = root.querySelector<HTMLCanvasElement>(`.${styles.canvas}`);
    if (!btn || !canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    const COLORS = ["#5b8cf8", "#ff9ebb", "#4cd4a6", "#b9a0ff"];

    // 계산 겹: 조각마다 각도·속도 값을 난수로 부여하고, 매 프레임 중력(GRAVITY)을 속도에
    // 더하고 속도에 감쇠(DRAG)를 곱해 궤적을 계산한다. 회전 값도 각자 다른 속도로 누적하고
    // 투명도 값은 남은 수명 비율로 계산해 사라진다.
    const GRAVITY = 420, DRAG = 0.985, LIFE = 900;
    let particles: Particle[] = [];
    let raf: number | null = null;
    let lastT = 0;

    function burst() {
      const cx = canvas!.width / 2, cy = canvas!.height * 0.35;
      particles = [];
      for (let i = 0; i < 18; i++) {
        const angle = (Math.PI * 2 * i) / 18 + (Math.random() - 0.5) * 0.5;
        const speed = 90 + Math.random() * 110;
        particles.push({
          x: cx, y: cy,
          vx: Math.cos(angle) * speed,
          vy: Math.sin(angle) * speed - 60,
          rot: Math.random() * Math.PI,
          vrot: (Math.random() - 0.5) * 10,
          color: COLORS[i % COLORS.length],
          age: 0,
        });
      }
      if (raf === null) { lastT = performance.now(); raf = requestAnimationFrame(tick); }
    }

    function tick(now: number) {
      const dt = Math.min((now - lastT) / 1000, 0.05);
      lastT = now;
      ctx!.clearRect(0, 0, canvas!.width, canvas!.height);
      let alive = false;
      for (const p of particles) {
        p.age += dt * 1000;
        if (p.age >= LIFE) continue;
        alive = true;
        p.vy += GRAVITY * dt;
        p.vx *= DRAG; p.vy *= DRAG;
        p.x += p.vx * dt; p.y += p.vy * dt;
        p.rot += p.vrot * dt;
        const op = Math.max(0, 1 - p.age / LIFE);
        ctx!.save();
        ctx!.globalAlpha = op;
        ctx!.translate(p.x, p.y);
        ctx!.rotate(p.rot);
        ctx!.fillStyle = p.color;
        ctx!.fillRect(-4, -3, 8, 6);
        ctx!.restore();
      }
      raf = alive ? requestAnimationFrame(tick) : null;
    }

    function onClick() { stopAutoplay(); burst(); }
    btn.addEventListener("click", onClick);

    let autoplayTimer: number | null = null;
    function stopAutoplay() { if (autoplayTimer !== null) { window.clearInterval(autoplayTimer); autoplayTimer = null; } }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoplayTimer = window.setInterval(burst, 1100); }

    return () => {
      stopAutoplay();
      if (raf !== null) { cancelAnimationFrame(raf); }
      btn.removeEventListener("click", onClick);
    };
  }, []);

  return (
    <div ref={rootRef} className={styles.stage}>
      <div className={styles.panel}>
        <div className={styles.wrap}>
          <canvas className={styles.canvas} width={220} height={120} />
          <button className={styles.btn} type="button" style={{ background: color }}>구매 완료</button>
        </div>
        <span className={styles.hint}>클릭하면 조각이 사방으로 흩어집니다</span>
      </div>
    </div>
  );
}