03Icon ripple spreading from the exact press point

<main class="stage">
  <section class="rp is-demo" id="rp" aria-label="An icon button rippling from the press point">
    <button class="rp__btn" type="button" id="rp-btn" aria-label="Open alerts">
      <span class="rp__seed" aria-hidden="true"></span>
      <span class="rp__seed rp__seed--b" aria-hidden="true"></span>
      <span class="rp__ic" aria-hidden="true"><svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor"><path d="M208,192H48a8,8,0,0,1-6.88-12C47.71,168.6,56,139.81,56,104a72,72,0,0,1,144,0c0,35.82,8.3,64.6,14.9,76A8,8,0,0,1,208,192Z" opacity=".2"/><path d="M221.8,175.94C216.25,166.38,208,139.33,208,104a80,80,0,1,0-160,0c0,35.34-8.26,62.38-13.81,71.94A16,16,0,0,0,48,200H88.81a40,40,0,0,0,78.38,0H208a16,16,0,0,0,13.8-24.06ZM128,216a24,24,0,0,1-22.62-16h45.24A24,24,0,0,1,128,216ZM48,184c7.7-13.24,16-43.92,16-80a64,64,0,1,1,128,0c0,36.05,8.28,66.73,16,80Z"/></svg></span>
      <span class="rp__dot" aria-hidden="true"></span>
    </button>
    <p class="rp__hint" id="rp-hint">Press anywhere on the button</p>
  </section>
</main>

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

// 눌린 자리에서 번지는 아이콘 리플 — 원은 transform · opacity 로만 움직인다
$duration: $dur-base;
$easing: $ease-out;
$color: $subject-cream;

@include stage($stage-orange);

.rp {
  display: grid;
  justify-items: center;
  gap: $sp-3;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.rp__btn {
  position: relative;
  display: inline-grid;
  place-items: center;
  width: 96px;
  height: 96px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: $subject-ink;
  color: $color;
  font-size: 46px;
  line-height: 1;
  cursor: pointer;
  overflow: hidden;
  transition: transform $dur-instant $ease-pop;
}
.rp__btn:focus-visible { outline: 3px solid $color; outline-offset: 3px; }
.rp__btn:active { transform: scale(.93); }

.rp__ic { display: inline-flex; }
.rp__dot {
  position: absolute;
  top: $sp-2;
  right: $sp-2;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: $stage-orange;
}

// 눌린 지점에서 퍼지는 원 — 좌표는 --x · --y 로 받고 크기는 scale
.rp__wave,
.rp__seed {
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: rgba(255, 247, 230, .5);
  transform: translate(-50%, -50%) scale(0);
  pointer-events: none;
}
@keyframes rp-grow {
  0% { transform: translate(-50%, -50%) scale(0); opacity: .55; }
  70% { opacity: .2; }
  100% { transform: translate(-50%, -50%) scale(9); opacity: 0; }
}
.rp__wave { animation-name: rp-grow; animation-duration: 600ms; animation-timing-function: $ease-out; animation-iteration-count: 1; }

.rp__hint {
  margin: 0;
  color: $subject-ink;
  font-size: 13px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
}

// ── 격자 미리보기 전용 2초 루프: 서로 다른 지점 두 곳에서 번진다 ──
.rp__seed {
  --x: 30%;
  --y: 34%;
}
.rp__seed.rp__seed--b { --x: 62%; --y: 66%; }
@keyframes rp-seed-a {
  0%, 16% { transform: translate(-50%, -50%) scale(0); opacity: 0; }
  17% { opacity: .55; }
  17.01% { transform: translate(-50%, -50%) scale(0); }
  46%, 100% { transform: translate(-50%, -50%) scale(9); opacity: 0; }
}
@keyframes rp-seed-b {
  0%, 56% { transform: translate(-50%, -50%) scale(0); opacity: 0; }
  57% { opacity: .55; }
  57.01% { transform: translate(-50%, -50%) scale(0); }
  86%, 100% { transform: translate(-50%, -50%) scale(9); opacity: 0; }
}
@keyframes rp-press {
  0%, 15% { transform: scale(1); }
  18% { transform: scale(.93); }
  26%, 55% { transform: scale(1); }
  58% { transform: scale(.93); }
  66%, 100% { transform: scale(1); }
}
.rp.is-demo .rp__seed:not(.rp__seed--b) {
  animation-name: rp-seed-a;
  animation-duration: $dur-loop;
  animation-timing-function: $ease-out;
  animation-iteration-count: infinite;
}
.rp.is-demo .rp__seed--b {
  animation-name: rp-seed-b;
  animation-duration: $dur-loop;
  animation-timing-function: $ease-out;
  animation-iteration-count: infinite;
}
.rp.is-demo .rp__btn {
  animation-name: rp-press;
  animation-duration: $dur-loop;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .rp__btn { width: 76px; height: 76px; font-size: 36px; }
  .rp__hint { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .rp.is-demo .rp__seed,
  .rp.is-demo .rp__btn { animation: none !important; transform: none !important; }
  .rp__wave { animation: none !important; opacity: 0 !important; }
  .rp__seed { opacity: 0 !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);
}

.rp {
  display: grid;
  justify-items: center;
  gap: 12px;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.rp__btn {
  position: relative;
  display: inline-grid;
  place-items: center;
  width: 96px;
  height: 96px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: #17141a;
  color: #fff7e6;
  font-size: 46px;
  line-height: 1;
  cursor: pointer;
  overflow: hidden;
  transition: transform 140ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.rp__btn:focus-visible {
  outline: 3px solid #fff7e6;
  outline-offset: 3px;
}

.rp__btn:active {
  transform: scale(0.93);
}

.rp__ic {
  display: inline-flex;
}

.rp__dot {
  position: absolute;
  top: 8px;
  right: 8px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #ff4d1f;
}

.rp__wave,
.rp__seed {
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: rgba(255, 247, 230, 0.5);
  transform: translate(-50%, -50%) scale(0);
  pointer-events: none;
}

@keyframes rp-grow {
  0% {
    transform: translate(-50%, -50%) scale(0);
    opacity: 0.55;
  }
  70% {
    opacity: 0.2;
  }
  100% {
    transform: translate(-50%, -50%) scale(9);
    opacity: 0;
  }
}
.rp__wave {
  animation-name: rp-grow;
  animation-duration: 600ms;
  animation-timing-function: ease-out;
  animation-iteration-count: 1;
}

.rp__hint {
  margin: 0;
  color: #17141a;
  font-size: 13px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
}

.rp__seed {
  --x: 30%;
  --y: 34%;
}

.rp__seed.rp__seed--b {
  --x: 62%;
  --y: 66%;
}

@keyframes rp-seed-a {
  0%, 16% {
    transform: translate(-50%, -50%) scale(0);
    opacity: 0;
  }
  17% {
    opacity: 0.55;
  }
  17.01% {
    transform: translate(-50%, -50%) scale(0);
  }
  46%, 100% {
    transform: translate(-50%, -50%) scale(9);
    opacity: 0;
  }
}
@keyframes rp-seed-b {
  0%, 56% {
    transform: translate(-50%, -50%) scale(0);
    opacity: 0;
  }
  57% {
    opacity: 0.55;
  }
  57.01% {
    transform: translate(-50%, -50%) scale(0);
  }
  86%, 100% {
    transform: translate(-50%, -50%) scale(9);
    opacity: 0;
  }
}
@keyframes rp-press {
  0%, 15% {
    transform: scale(1);
  }
  18% {
    transform: scale(0.93);
  }
  26%, 55% {
    transform: scale(1);
  }
  58% {
    transform: scale(0.93);
  }
  66%, 100% {
    transform: scale(1);
  }
}
.rp.is-demo .rp__seed:not(.rp__seed--b) {
  animation-name: rp-seed-a;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

.rp.is-demo .rp__seed--b {
  animation-name: rp-seed-b;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

.rp.is-demo .rp__btn {
  animation-name: rp-press;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .rp__btn {
    width: 76px;
    height: 76px;
    font-size: 36px;
  }
  .rp__hint {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rp.is-demo .rp__seed,
  .rp.is-demo .rp__btn {
    animation: none !important;
    transform: none !important;
  }
  .rp__wave {
    animation: none !important;
    opacity: 0 !important;
  }
  .rp__seed {
    opacity: 0 !important;
  }
}

// 눌린 지점 리플: pointerdown 이 좌표를 잡아 --x · --y 로 옮겨 적는다 (10줄 안팎)
var rp = document.getElementById('rp');
var rpBtn = document.getElementById('rp-btn');
var rpHint = document.getElementById('rp-hint');
rpBtn.addEventListener('pointerdown', function (e) {
  rp.classList.remove('is-demo');
  var box = rpBtn.getBoundingClientRect();
  var dot = document.createElement('span');
  dot.className = 'rp__wave';
  dot.style.setProperty('--x', (e.clientX - box.left) + 'px');
  dot.style.setProperty('--y', (e.clientY - box.top) + 'px');
  rpBtn.appendChild(dot);
  window.setTimeout(function () { dot.remove(); }, 620);
  rpHint.textContent = 'Alerts checked';
});
rpBtn.addEventListener('keydown', function (e) {
  if (e.key !== 'Enter' && e.key !== ' ') return;
  rpHint.textContent = 'Alerts checked';
});

import { useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent } from "react";
import styles from "./PointRippleButton.module.scss";

export type PointRippleButtonProps = {
  buttonLabel?: string;
  hintIdle?: string;
  hintDone?: string;
  groupLabel?: string;
  /** 오른쪽 위 안 읽은 표시 */
  unread?: boolean;
  /** 격자 미리보기용 2초 자동 루프. 사람이 손대면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type WaveVars = CSSProperties & { "--x": string; "--y": string };
// ambient 가 얇아 KeyboardEvent 를 못 쓴다 — 필요한 꼴만 로컬 타입으로 선언
type KeyEvt = { key: string };
type Wave = { id: number; x: number; y: number };

export default function PointRippleButton({
  buttonLabel = "Open notifications",
  hintIdle = "Press anywhere on the button",
  hintDone = "Notifications opened",
  groupLabel = "Icon button that ripples from the pressed point",
  unread = true,
  demo = true,
  duration = 300,
  easing = "ease-out",
  color = "#fff7e6",
}: PointRippleButtonProps) {
  const [waves, setWaves] = useState<Wave[]>([]);
  const [live, setLive] = useState(demo);
  const [hint, setHint] = useState(hintIdle);
  const seq = useRef<number>(0);
  const timers = useRef<number[]>([]);

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const life = duration * 2;      // 리플 한 번의 수명 — scss 의 calc(var(--duration) * 2) 와 같다

  useEffect(() => () => {
    const list = timers.current;
    if (!list) return;
    for (const t of list) window.clearTimeout(t);
  }, []);

  // 눌린 지점을 --x · --y 로 옮겨 적는다. 원은 transform · opacity 로만 커진다
  function onPointerDown(e: PointerEvent<HTMLButtonElement>) {
    setLive(false);
    const box = e.currentTarget.getBoundingClientRect();
    const id = (seq.current === null ? 0 : seq.current) + 1;   // useRef 는 T|null 이라 null 가드
    seq.current = id;
    setWaves((prev) => prev.concat([{ id, x: e.clientX - box.left, y: e.clientY - box.top }]));
    setHint(hintDone);
    const t = window.setTimeout(() => {
      setWaves((prev) => prev.filter((w) => w.id !== id));
    }, life + 20);
    const list = timers.current;
    if (list) list.push(t);
  }

  function onKeyDown(e: KeyEvt) {
    if (e.key !== "Enter" && e.key !== " ") return;
    setLive(false);
    setHint(hintDone);
  }

  const cls = [styles.rp, live ? styles.isDemo : ""].filter(Boolean).join(" ");

  return (
    <section className={cls} style={vars} aria-label={groupLabel}>
      <button
        className={styles.btn}
        type="button"
        aria-label={buttonLabel}
        onPointerDown={onPointerDown}
        onKeyDown={onKeyDown}
      >
        <span className={styles.seed} aria-hidden="true" />
        <span className={[styles.seed, styles.seedB].join(" ")} aria-hidden="true" />
        <span className={styles.ic} aria-hidden="true">
          <svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor"><path d="M208,192H48a8,8,0,0,1-6.88-12C47.71,168.6,56,139.81,56,104a72,72,0,0,1,144,0c0,35.82,8.3,64.6,14.9,76A8,8,0,0,1,208,192Z" opacity=".2"/><path d="M221.8,175.94C216.25,166.38,208,139.33,208,104a80,80,0,1,0-160,0c0,35.34-8.26,62.38-13.81,71.94A16,16,0,0,0,48,200H88.81a40,40,0,0,0,78.38,0H208a16,16,0,0,0,13.8-24.06ZM128,216a24,24,0,0,1-22.62-16h45.24A24,24,0,0,1,128,216ZM48,184c7.7-13.24,16-43.92,16-80a64,64,0,1,1,128,0c0,36.05,8.28,66.73,16,80Z"/></svg>
        </span>
        {unread && <span className={styles.dot} aria-hidden="true" />}
        {waves.map((w) => {
          const wv: WaveVars = { "--x": `${w.x}px`, "--y": `${w.y}px` };
          return <span className={styles.wave} style={wv} key={w.id} aria-hidden="true" />;
        })}
      </button>
      <p className={styles.hint}>{hint}</p>
    </section>
  );
}