05パドルバウンド

<svg width="0" height="0" style="position:absolute" aria-hidden="true">
  <defs>
    <symbol id="ico-ball" viewBox="0 0 256 256" fill="currentColor"><g><path d="M224 128a96 96 0 1 1-96-96a96 96 0 0 1 96 96" opacity=".2"/><path d="M128 24a104 104 0 1 0 104 104A104.11 104.11 0 0 0 128 24m0 192a88 88 0 1 1 88-88a88.1 88.1 0 0 1-88 88"/></g></symbol>
    <symbol id="ico-reset" viewBox="0 0 256 256" fill="currentColor"><g><path d="M232 136a104 104 0 1 1-38.17-80.55L208 60v-4a8 8 0 0 1 16 0v34a8 8 0 0 1-8 8h-34a8 8 0 0 1 0-16h7.6l-8.89-7.4A88 88 0 1 0 216 136a8 8 0 0 1 16 0Z" opacity=".2"/><path d="M232 136a104 104 0 1 1-38.17-80.55L208 60v-4a8 8 0 0 1 16 0v34a8 8 0 0 1-8 8h-34a8 8 0 0 1 0-16h7.6l-8.89-7.4A88 88 0 1 0 216 136a8 8 0 0 1 16 0Z"/></g></symbol>
  </defs>
</svg>
<main class="stage">
<div class="pb is-demo" id="pb">
  <p class="pb__hint"><svg class="pb__ico" aria-hidden="true"><use href="#ico-ball"/></svg><span>パドルがマウスを追い、ボールがレンガに当たるたびスコアが上がります</span></p>
  <div class="pb__field" id="field" role="application" aria-label="レンガのゲーム盤" tabindex="0">
    <p class="pb__score" aria-live="polite"><span class="pb__scoreVal" id="scoreText">スコア 0</span><span class="pb__scoreLoop" aria-hidden="true"><i>スコア 0</i><i>スコア 1</i><i>スコア 2</i></span></p>
    <div class="pb__bricks" id="bricks" aria-hidden="true"></div>
    <span class="pb__ball" id="ball" aria-hidden="true"></span>
    <span class="pb__paddle" id="paddle" aria-hidden="true"></span>
  </div>
  <div class="pb__bar">
    <button class="pb__launch" id="launch" type="button">
      <svg class="pb__ico" aria-hidden="true"><use href="#ico-ball"/></svg><span>ボールを放つ</span>
    </button>
    <button class="pb__reset" id="reset" type="button">
      <svg class="pb__ico" aria-hidden="true"><use href="#ico-reset"/></svg><span>最初へ</span>
    </button>
  </div>
</div>
</main>

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

// 패들 튕기기 — 공은 속도 벡터를 법선으로 되돌리는 반사, 패들은 맞은 칸에 따라 수평 성분이 꺾인다.
// 패들은 pointermove(마우스) 와 keydown(방향키) 두 경로가 같은 px 값을 공유한다.
// 격자 미리보기(.is-demo)는 실제 게임의 왕복을 표본 추출한 공 경로 + 패들 추적 + 벽돌 섬광을 키프레임으로 재생한다.
// 루프의 시작과 끝을 패들 접촉점 한 곳에 두어 경계가 곧 패들 튕김이라 순간이동이 보이지 않는다.

$duration: $dur-loop;
$easing: linear;      // 공은 등속 — 왕복 속도는 키프레임 간 거리 비율로 표본화했다
$color: $stage-yellow;

@include stage($stage-ink);

.pb { --kx: 1; --ky: 1; display: flex; flex-direction: column; gap: $sp-3; width: 100%; max-width: 424px; }
.pb__hint {
  display: flex; align-items: center; gap: $sp-1; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); color: $subject-cream;
}
.pb__ico { width: 16px; height: 16px; flex: 0 0 auto; color: $color; }

.pb__field {
  position: relative; height: 176px; border-radius: $r-card;
  background: rgba($subject-cream, .06);
  box-shadow: inset 0 0 0 1px rgba($subject-cream, .14);
  overflow: hidden; touch-action: none; cursor: none;
}
.pb__field:focus-visible { outline: 2px solid $color; outline-offset: 2px; }

.pb__bricks { position: absolute; inset: 0; }
.pb__brick {
  position: absolute; left: 0; top: 0; width: 60px; height: 14px;
  border-radius: $r-xs;
}
.pb__brick--r0 { background: $stage-orange; }
.pb__brick--r1 { background: $color; }
.pb__brick--r2 { background: $subject-cream; }
.pb__brick.is-hit { visibility: hidden; }

.pb__ball {
  position: absolute; left: 0; top: 0; width: 12px; height: 12px;
  border-radius: 50%; background: $subject-cream;
}
.pb__paddle {
  position: absolute; left: 0; top: 0; width: 68px; height: 10px;
  border-radius: $r-pill; background: $color;
}

.pb__score {
  position: absolute; left: $sp-2; top: $sp-1; margin: 0;
  font-weight: 800; font-size: clamp(10px, 2.6vw, 11px); color: $subject-cream;
  z-index: 1;
}
.pb__scoreLoop { position: absolute; inset: 0; display: grid; visibility: hidden; }
.pb__scoreLoop i { grid-area: 1 / 1; font-style: normal; visibility: hidden; }

.pb__bar { display: flex; align-items: center; justify-content: flex-end; gap: $sp-2; flex-wrap: wrap; }
.pb__launch, .pb__reset {
  display: inline-flex; align-items: center; gap: $sp-1; border: 0; border-radius: $r-pill;
  padding: $sp-1 $sp-3; background: $color; color: $subject-ink; cursor: pointer;
  font-family: inherit; font-weight: 800; font-size: clamp(10px, 2.6vw, 11px); line-height: 1;
}
.pb__launch .pb__ico, .pb__reset .pb__ico { color: $subject-ink; }

// ── 격자 미리보기 루프 ─────────────────────────────────────────────
// 공 경로: 패들 접촉(0%) → 벽돌 3회 섬광 → 벽 2회 → 패들 접촉 2회 → 하강(94%) → 같은 접촉점(100%).
// 100% 와 0% 가 같은 점이라 경계가 닫혀 있고, 그 모서리는 패들 튕김으로 읽힌다.
.pb.is-demo .pb__ball {
  animation-name: pbBall; animation-duration: $duration; animation-timing-function: $easing;
  animation-iteration-count: infinite; animation-fill-mode: backwards;
}
@keyframes pbBall {
  0%   { transform: translate(calc(var(--kx) * 210px), calc(var(--ky) * 158px)); }
  9%   { transform: translate(calc(var(--kx) * 318px), calc(var(--ky) * 40px)); }
  17%  { transform: translate(calc(var(--kx) * 398px), calc(var(--ky) * 116px)); }
  25%  { transform: translate(calc(var(--kx) * 306px), calc(var(--ky) * 158px)); }
  33%  { transform: translate(calc(var(--kx) * 252px), calc(var(--ky) * 48px)); }
  41%  { transform: translate(calc(var(--kx) * 128px), calc(var(--ky) * 52px)); }
  49%  { transform: translate(calc(var(--kx) * 24px), calc(var(--ky) * 116px)); }
  57%  { transform: translate(calc(var(--kx) * 110px), calc(var(--ky) * 158px)); }
  65%  { transform: translate(calc(var(--kx) * 196px), calc(var(--ky) * 100px)); }
  73%  { transform: translate(calc(var(--kx) * 280px), calc(var(--ky) * 20px)); }
  81%  { transform: translate(calc(var(--kx) * 398px), calc(var(--ky) * 84px)); }
  89%  { transform: translate(calc(var(--kx) * 330px), calc(var(--ky) * 130px)); }
  94%  { transform: translate(calc(var(--kx) * 160px), calc(var(--ky) * 134px)); }
  100% { transform: translate(calc(var(--kx) * 210px), calc(var(--ky) * 158px)); }
}
// 패들 추적 — 공이 패들 선에 닿는 순간(0/25/57/96%) 의 x 로 맞춰 간다
.pb.is-demo .pb__paddle {
  animation-name: pbPaddle; animation-duration: $duration; animation-timing-function: ease-in-out;
  animation-iteration-count: infinite;
}
@keyframes pbPaddle {
  0%   { transform: translate(calc(var(--kx) * 176px), calc(var(--ky) * 158px)); }
  9%   { transform: translate(calc(var(--kx) * 284px), calc(var(--ky) * 158px)); }
  25%  { transform: translate(calc(var(--kx) * 272px), calc(var(--ky) * 158px)); }
  41%  { transform: translate(calc(var(--kx) * 94px),  calc(var(--ky) * 158px)); }
  57%  { transform: translate(calc(var(--kx) * 76px),  calc(var(--ky) * 158px)); }
  73%  { transform: translate(calc(var(--kx) * 246px), calc(var(--ky) * 158px)); }
  89%  { transform: translate(calc(var(--kx) * 296px), calc(var(--ky) * 158px)); }
  96%  { transform: translate(calc(var(--kx) * 136px), calc(var(--ky) * 158px)); }
  100% { transform: translate(calc(var(--kx) * 176px), calc(var(--ky) * 158px)); }
}
// 벽돌 섬광 — 공이 닿는 9%(r1c4)·33%(r2c3)·41%(r2c1)·73%(r0c4) 에 반투명 스윕.
// 사라지지 않고 반짝이기만 해서 루프 경계에 되살아나는 순간이동이 없다.
.pb.is-demo .pb__brick--r1c4 { animation: pbFlash $duration linear infinite; animation-delay: 0ms; }
.pb.is-demo .pb__brick--r2c3 { animation: pbFlash $duration linear infinite; animation-delay: 460ms; }
.pb.is-demo .pb__brick--r2c1 { animation: pbFlash $duration linear infinite; animation-delay: 620ms; }
.pb.is-demo .pb__brick--r0c4 { animation: pbFlash $duration linear infinite; animation-delay: 1260ms; }
@keyframes pbFlash {
  0%, 7%, 13%, 100% { opacity: 1; }
  10% { opacity: .3; }
}
// 점수 교체 — 0→1(9%)→2(33%)→0(96%). steps 컷이라 반투명 겹침이 없다
.pb.is-demo .pb__scoreVal { color: transparent; }
.pb.is-demo .pb__scoreLoop { visibility: visible; }
.pb.is-demo .pb__scoreLoop i {
  animation-duration: $duration; animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.pb.is-demo .pb__scoreLoop i:nth-child(1) { animation-name: pbScore0; }
.pb.is-demo .pb__scoreLoop i:nth-child(2) { animation-name: pbScore1; }
.pb.is-demo .pb__scoreLoop i:nth-child(3) { animation-name: pbScore2; }
@keyframes pbScore0 { 0%, 8% { visibility: visible; } 9%, 95% { visibility: hidden; } 96%, 100% { visibility: visible; } }
@keyframes pbScore1 { 0%, 8% { visibility: hidden; } 9%, 32% { visibility: visible; } 33%, 100% { visibility: hidden; } }
@keyframes pbScore2 { 0%, 32% { visibility: hidden; } 33%, 95% { visibility: visible; } 96%, 100% { visibility: hidden; } }

@media (max-width: 340px) {
  .pb { --kx: .68; --ky: .59; gap: $sp-2; }
  .pb__field { height: 104px; }
  .pb__brick { width: 40px; height: 10px; }
  .pb__paddle { width: 52px; height: 8px; }
  .pb__ball { width: 10px; height: 10px; }
}

// reduce 에서는 패들 위에 공이 얹힌 정지 상태 한 장을 둔다
@media (prefers-reduced-motion: reduce) {
  .pb.is-demo .pb__ball,
  .pb.is-demo .pb__paddle,
  .pb.is-demo .pb__brick,
  .pb.is-demo .pb__scoreLoop i { animation: none !important; }
  .pb.is-demo .pb__ball { transform: translate(calc(var(--kx) * 210px), calc(var(--ky) * 144px)) !important; }
  .pb.is-demo .pb__paddle { transform: translate(calc(var(--kx) * 176px), calc(var(--ky) * 158px)) !important; }
  .pb.is-demo .pb__scoreVal { color: $subject-cream !important; }
  .pb.is-demo .pb__scoreLoop { visibility: hidden !important; }
}

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);
}

.pb {
  --kx: 1;
  --ky: 1;
  display: flex;
  flex-direction: column;
  gap: 12px;
  width: 100%;
  max-width: 424px;
}

.pb__hint {
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  color: #fff7e6;
}

.pb__ico {
  width: 16px;
  height: 16px;
  flex: 0 0 auto;
  color: #ffd23f;
}

.pb__field {
  position: relative;
  height: 176px;
  border-radius: 16px;
  background: rgba(255, 247, 230, 0.06);
  box-shadow: inset 0 0 0 1px rgba(255, 247, 230, 0.14);
  overflow: hidden;
  touch-action: none;
  cursor: none;
}

.pb__field:focus-visible {
  outline: 2px solid #ffd23f;
  outline-offset: 2px;
}

.pb__bricks {
  position: absolute;
  inset: 0;
}

.pb__brick {
  position: absolute;
  left: 0;
  top: 0;
  width: 60px;
  height: 14px;
  border-radius: 4px;
}

.pb__brick--r0 {
  background: #ff4d1f;
}

.pb__brick--r1 {
  background: #ffd23f;
}

.pb__brick--r2 {
  background: #fff7e6;
}

.pb__brick.is-hit {
  visibility: hidden;
}

.pb__ball {
  position: absolute;
  left: 0;
  top: 0;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: #fff7e6;
}

.pb__paddle {
  position: absolute;
  left: 0;
  top: 0;
  width: 68px;
  height: 10px;
  border-radius: 999px;
  background: #ffd23f;
}

.pb__score {
  position: absolute;
  left: 8px;
  top: 4px;
  margin: 0;
  font-weight: 800;
  font-size: clamp(10px, 2.6vw, 11px);
  color: #fff7e6;
  z-index: 1;
}

.pb__scoreLoop {
  position: absolute;
  inset: 0;
  display: grid;
  visibility: hidden;
}

.pb__scoreLoop i {
  grid-area: 1/1;
  font-style: normal;
  visibility: hidden;
}

.pb__bar {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 8px;
  flex-wrap: wrap;
}

.pb__launch, .pb__reset {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  border: 0;
  border-radius: 999px;
  padding: 4px 12px;
  background: #ffd23f;
  color: #17141a;
  cursor: pointer;
  font-family: inherit;
  font-weight: 800;
  font-size: clamp(10px, 2.6vw, 11px);
  line-height: 1;
}

.pb__launch .pb__ico, .pb__reset .pb__ico {
  color: #17141a;
}

.pb.is-demo .pb__ball {
  animation-name: pbBall;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
  animation-fill-mode: backwards;
}

@keyframes pbBall {
  0% {
    transform: translate(calc(var(--kx) * 210px), calc(var(--ky) * 158px));
  }
  9% {
    transform: translate(calc(var(--kx) * 318px), calc(var(--ky) * 40px));
  }
  17% {
    transform: translate(calc(var(--kx) * 398px), calc(var(--ky) * 116px));
  }
  25% {
    transform: translate(calc(var(--kx) * 306px), calc(var(--ky) * 158px));
  }
  33% {
    transform: translate(calc(var(--kx) * 252px), calc(var(--ky) * 48px));
  }
  41% {
    transform: translate(calc(var(--kx) * 128px), calc(var(--ky) * 52px));
  }
  49% {
    transform: translate(calc(var(--kx) * 24px), calc(var(--ky) * 116px));
  }
  57% {
    transform: translate(calc(var(--kx) * 110px), calc(var(--ky) * 158px));
  }
  65% {
    transform: translate(calc(var(--kx) * 196px), calc(var(--ky) * 100px));
  }
  73% {
    transform: translate(calc(var(--kx) * 280px), calc(var(--ky) * 20px));
  }
  81% {
    transform: translate(calc(var(--kx) * 398px), calc(var(--ky) * 84px));
  }
  89% {
    transform: translate(calc(var(--kx) * 330px), calc(var(--ky) * 130px));
  }
  94% {
    transform: translate(calc(var(--kx) * 160px), calc(var(--ky) * 134px));
  }
  100% {
    transform: translate(calc(var(--kx) * 210px), calc(var(--ky) * 158px));
  }
}
.pb.is-demo .pb__paddle {
  animation-name: pbPaddle;
  animation-duration: 2s;
  animation-timing-function: ease-in-out;
  animation-iteration-count: infinite;
}

@keyframes pbPaddle {
  0% {
    transform: translate(calc(var(--kx) * 176px), calc(var(--ky) * 158px));
  }
  9% {
    transform: translate(calc(var(--kx) * 284px), calc(var(--ky) * 158px));
  }
  25% {
    transform: translate(calc(var(--kx) * 272px), calc(var(--ky) * 158px));
  }
  41% {
    transform: translate(calc(var(--kx) * 94px), calc(var(--ky) * 158px));
  }
  57% {
    transform: translate(calc(var(--kx) * 76px), calc(var(--ky) * 158px));
  }
  73% {
    transform: translate(calc(var(--kx) * 246px), calc(var(--ky) * 158px));
  }
  89% {
    transform: translate(calc(var(--kx) * 296px), calc(var(--ky) * 158px));
  }
  96% {
    transform: translate(calc(var(--kx) * 136px), calc(var(--ky) * 158px));
  }
  100% {
    transform: translate(calc(var(--kx) * 176px), calc(var(--ky) * 158px));
  }
}
.pb.is-demo .pb__brick--r1c4 {
  animation: pbFlash 2s linear infinite;
  animation-delay: 0ms;
}

.pb.is-demo .pb__brick--r2c3 {
  animation: pbFlash 2s linear infinite;
  animation-delay: 460ms;
}

.pb.is-demo .pb__brick--r2c1 {
  animation: pbFlash 2s linear infinite;
  animation-delay: 620ms;
}

.pb.is-demo .pb__brick--r0c4 {
  animation: pbFlash 2s linear infinite;
  animation-delay: 1260ms;
}

@keyframes pbFlash {
  0%, 7%, 13%, 100% {
    opacity: 1;
  }
  10% {
    opacity: 0.3;
  }
}
.pb.is-demo .pb__scoreVal {
  color: transparent;
}

.pb.is-demo .pb__scoreLoop {
  visibility: visible;
}

.pb.is-demo .pb__scoreLoop i {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.pb.is-demo .pb__scoreLoop i:nth-child(1) {
  animation-name: pbScore0;
}

.pb.is-demo .pb__scoreLoop i:nth-child(2) {
  animation-name: pbScore1;
}

.pb.is-demo .pb__scoreLoop i:nth-child(3) {
  animation-name: pbScore2;
}

@keyframes pbScore0 {
  0%, 8% {
    visibility: visible;
  }
  9%, 95% {
    visibility: hidden;
  }
  96%, 100% {
    visibility: visible;
  }
}
@keyframes pbScore1 {
  0%, 8% {
    visibility: hidden;
  }
  9%, 32% {
    visibility: visible;
  }
  33%, 100% {
    visibility: hidden;
  }
}
@keyframes pbScore2 {
  0%, 32% {
    visibility: hidden;
  }
  33%, 95% {
    visibility: visible;
  }
  96%, 100% {
    visibility: hidden;
  }
}
@media (max-width: 340px) {
  .pb {
    --kx: .68;
    --ky: .59;
    gap: 8px;
  }
  .pb__field {
    height: 104px;
  }
  .pb__brick {
    width: 40px;
    height: 10px;
  }
  .pb__paddle {
    width: 52px;
    height: 8px;
  }
  .pb__ball {
    width: 10px;
    height: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .pb.is-demo .pb__ball,
  .pb.is-demo .pb__paddle,
  .pb.is-demo .pb__brick,
  .pb.is-demo .pb__scoreLoop i {
    animation: none !important;
  }
  .pb.is-demo .pb__ball {
    transform: translate(calc(var(--kx) * 210px), calc(var(--ky) * 144px)) !important;
  }
  .pb.is-demo .pb__paddle {
    transform: translate(calc(var(--kx) * 176px), calc(var(--ky) * 158px)) !important;
  }
  .pb.is-demo .pb__scoreVal {
    color: #fff7e6 !important;
  }
  .pb.is-demo .pb__scoreLoop {
    visibility: hidden !important;
  }
}

var root = document.getElementById('pb');
var field = document.getElementById('field');
var bricksBox = document.getElementById('bricks');
var ball = document.getElementById('ball');
var paddle = document.getElementById('paddle');
var scoreText = document.getElementById('scoreText');
var SCORE_LABEL = 'スコア';
var reduce = window.matchMedia('(prefers-reduced-motion: reduce)');
// 벽돌 3×6 — 左 여백 22, 위 여백 24, 칸 60×14, 간격 4. 행 색은 CSS 클래스가 정한다.
// 격자의 원점은 여기 한 곳뿐이다 — 그리는 자리(laid)와 충돌 판정(step)이 같은 BX·BY 를 본다.
// 두 곳에 따로 적으면 위 여백만 옮기는 순간 공이 보이지 않는 띠에서 튕긴다
var COLS = 6, ROWS = 3, BX = 22, BY = 24, BW = 60, BH = 14, GAP = 4;
var bricks = [];
for (var r = 0; r < ROWS; r++) {
  for (var c = 0; c < COLS; c++) {
    var el = document.createElement('i');
    el.className = 'pb__brick pb__brick--r' + r + ' pb__brick--r' + r + 'c' + c;
    el.style.transform = 'translate(0, 0)';  // 실제 위치는 laid() 가 판 폭에 맞춰 넣는다
    bricksBox.appendChild(el);
    bricks.push({ el: el, r: r, c: c, alive: true });
  }
}
var PW = 68, PH = 10, SPEED = 240;
function padY() { return field.clientHeight - 18; }
var px = 176, bx = 210, by = 150, vx = SPEED * 0.66, vy = -SPEED * 0.75;
var stuck = true, score = 0, last = 0, running = false;

function scaled(n) { return n * field.clientWidth / 424; }
function laid() {
  for (var i = 0; i < bricks.length; i++) {
    var b = bricks[i];
    b.el.style.transform = 'translate(' + scaled(BX + b.c * (BW + GAP)) + 'px, ' + (BY + b.r * (BH + GAP)) + 'px)';
  }
}
function paint() {
  paddle.style.transform = 'translate(' + px + 'px, ' + padY() + 'px)';
  ball.style.transform = 'translate(' + bx + 'px, ' + by + 'px)';
}
function paintScore() {
  // 라벨을 낱말로 떼어 둬야 문구 사전(demo/문구.json)이 en·ja 로 바꿔 준다 — 붙여 쓴 'スコア ' 는 사전 키가 못 된다
  scoreText.textContent = SCORE_LABEL + ' ' + score;
}
function step(now) {
  var dt = Math.min((now - last) / 1000, 0.033);
  last = now;
  var w = field.clientWidth, h = field.clientHeight;
  if (stuck) { bx = px + PW / 2 - 6; by = padY() - 14; paint(); requestAnimationFrame(step); return; }
  bx += vx * dt; by += vy * dt;
  // 벽 반사 — 좌우와 천장
  if (bx < 0) { bx = 0; vx = Math.abs(vx); }
  if (bx > w - 12) { bx = w - 12; vx = -Math.abs(vx); }
  if (by < 0) { by = 0; vy = Math.abs(vy); }
  // 패들 반사 — 맞은 칸에 따라 수평 성분이 꺾인다 (법선 반사의 게임판 버전)
  var pyNow = padY();
  if (vy > 0 && by + 12 >= pyNow && by + 12 <= pyNow + PH && bx + 12 > px && bx < px + PW) {
    var off = (bx + 6 - (px + PW / 2)) / (PW / 2);
    vx = SPEED * off * 0.9;
    vy = -Math.abs(vy);
    by = pyNow - 12;
  }
  // 벽돌 충돌 — 겹친 칸을 끄고 뚫은 변으로 반사한다
  for (var i = 0; i < bricks.length; i++) {
    var b = bricks[i];
    if (!b.alive) { continue; }
    var bxx = scaled(BX + b.c * (BW + GAP)), byy = BY + b.r * (BH + GAP);
    if (bx + 12 > bxx && bx < bxx + scaled(BW) && by + 12 > byy && by < byy + BH) {
      b.alive = false;
      b.el.classList.add('is-hit');
      score += 1; paintScore();
      var overX = bx + 6 - (bxx + scaled(BW) / 2), overY = by + 6 - (byy + BH / 2);
      if (Math.abs(overX) > Math.abs(overY)) { vx = overX > 0 ? Math.abs(vx) : -Math.abs(vx); }
      else { vy = overY > 0 ? Math.abs(vy) : -Math.abs(vy); }
      break;
    }
  }
  // 공을 놓쳤으면 패들 위에 다시 얹는다
  if (by > h + 8) { stuck = true; bx = px + PW / 2 - 6; by = padY() - 14; }
  paint();
  requestAnimationFrame(step);
}
function wake() {
  root.classList.remove('is-demo');
  if (reduce.matches) {
    px = 176; stuck = true; bx = px + PW / 2 - 6; by = padY() - 14;
    paint(); paintScore(); return false;
  }
  if (!running) { running = true; last = performance.now(); requestAnimationFrame(step); }
  return true;
}
function movePaddle(x) {
  px = Math.max(0, Math.min(field.clientWidth - PW, x));
  if (!running) { wake(); }
}
field.addEventListener('pointermove', function (e) {
  var r = field.getBoundingClientRect();
  movePaddle(e.clientX - r.left - PW / 2);
});
field.addEventListener('keydown', function (e) {
  var JUMP = 30;
  if (e.key === 'ArrowLeft') { movePaddle(px - JUMP); }
  else if (e.key === 'ArrowRight') { movePaddle(px + JUMP); }
  else if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); launchBall(); }
  else { return; }
  e.preventDefault();
});
function launchBall() {
  wake();
  stuck = false;
  vx = SPEED * 0.66; vy = -SPEED * 0.75;
}
document.getElementById('launch').addEventListener('click', launchBall);
document.getElementById('reset').addEventListener('click', function () {
  for (var i = 0; i < bricks.length; i++) {
    bricks[i].alive = true; bricks[i].el.classList.remove('is-hit');
  }
  score = 0; paintScore(); stuck = true; px = 176;
  wake();
});
laid();
window.addEventListener('resize', laid);
paint(); paintScore();

// PaddleBounce — vanilla 판(run/292/demo/05-physics-paddle-bounce/index.html) 의 React 포트.
// 공은 등속으로 날고 벽·패들·벽돌에 부딪히면 뚫은 변의 법선으로 속도 부호를 되돌린다.
// 패들은 맞은 칸(off) 에 따라 수평 성분이 SPEED×off×0.9 로 꺾인다. 값·수치는 vanilla 와 같다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent as ReactPointerEvent } from "react";
import styles from "./PaddleBounce.module.scss";

export type PaddleBounceProps = {
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
// useRef 는 T | null 을 돌려준다. 처음부터 값이 있고 절대 비지 않는 상자는 이렇게 좁혀 쓴다
type Box<T> = { current: T };
// React 의 KeyboardEvent 제네릭이 없는 환경이라 필요한 것만 로컬로 선언한다
type KeyEvt = { key: string; preventDefault(): void };
type Brick = { el: HTMLElement; r: number; c: number; alive: boolean };

// 벽돌 3×6 — 왼쪽 여백 22, 위 여백 24, 칸 60×14, 간격 4. 행 색은 CSS 클래스가 정한다.
// 격자의 원점은 여기 한 곳뿐이다 — 그리는 자리(laid)와 충돌 판정(step)이 같은 BX·BY 를 본다.
// 두 곳에 따로 적으면 위 여백만 옮기는 순간 공이 보이지 않는 띠에서 튕긴다
const COLS = 6;
const ROWS = 3;
const BX = 22;
const BY = 24;
const BW = 60;
const BH = 14;
const GAP = 4;
const PW = 68;
const PH = 10;
const SPEED = 240;
const JUMP = 30;   // 방향키 한 번에 옮기는 패들 거리
const FIELD_LABEL = "벽돌 게임판";
const SCORE_LABEL = "점수";   // 문구 사전이 en·ja 로 바꿔 줄 수 있게 상수 하나로 둔다
const CELLS: { r: number; c: number }[] = [];
for (let r = 0; r < ROWS; r++) {
  for (let c = 0; c < COLS; c++) CELLS.push({ r: r, c: c });
}

export default function PaddleBounce({
  duration = 2000,
  easing = "linear",
  color = "#ffd23f",
}: PaddleBounceProps) {
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const bricksBoxRef = useRef<HTMLDivElement | null>(null);
  const ballRef = useRef<HTMLSpanElement | null>(null);
  const paddleRef = useRef<HTMLSpanElement | null>(null);
  const bricksRef = useRef<Brick[]>([]) as Box<Brick[]>;
  const pxRef = useRef<number>(176) as Box<number>;
  const bxRef = useRef<number>(210) as Box<number>;
  const byRef = useRef<number>(150) as Box<number>;
  const vxRef = useRef<number>(SPEED * 0.66) as Box<number>;
  const vyRef = useRef<number>(-SPEED * 0.75) as Box<number>;
  const stuckRef = useRef<boolean>(true) as Box<boolean>;
  const scoreRef = useRef<number>(0) as Box<number>;
  const lastRef = useRef<number>(0) as Box<number>;
  const rafRef = useRef<number>(0) as Box<number>;
  const runningRef = useRef<boolean>(false) as Box<boolean>;
  const [score, setScore] = useState(0);
  const [demo, setDemo] = useState(true);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

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

  function padY(): number {
    const field = fieldRef.current;
    return (field ? field.clientHeight : 176) - 18;
  }

  function scaled(n: number): number {
    const field = fieldRef.current;
    return field ? (n * field.clientWidth) / 424 : n;
  }

  function laid(): void {
    const bricks = bricksRef.current;
    for (let i = 0; i < bricks.length; i++) {
      const b = bricks[i];
      b.el.style.transform = "translate(" + scaled(BX + b.c * (BW + GAP)) + "px, " + (BY + b.r * (BH + GAP)) + "px)";
    }
  }

  function paint(): void {
    const paddle = paddleRef.current;
    const ball = ballRef.current;
    if (paddle) paddle.style.transform = "translate(" + pxRef.current + "px, " + padY() + "px)";
    if (ball) ball.style.transform = "translate(" + bxRef.current + "px, " + byRef.current + "px)";
  }

  function step(now: number): void {
    const field = fieldRef.current;
    if (!field) { runningRef.current = false; return; }
    const dt = Math.min((now - lastRef.current) / 1000, 0.033);
    lastRef.current = now;
    const w = field.clientWidth;
    const h = field.clientHeight;
    if (stuckRef.current) {
      bxRef.current = pxRef.current + PW / 2 - 6;
      byRef.current = padY() - 14;
      paint();
      rafRef.current = requestAnimationFrame(step);
      return;
    }
    bxRef.current += vxRef.current * dt;
    byRef.current += vyRef.current * dt;
    // 벽 반사 — 좌우와 천장
    if (bxRef.current < 0) { bxRef.current = 0; vxRef.current = Math.abs(vxRef.current); }
    if (bxRef.current > w - 12) { bxRef.current = w - 12; vxRef.current = -Math.abs(vxRef.current); }
    if (byRef.current < 0) { byRef.current = 0; vyRef.current = Math.abs(vyRef.current); }
    // 패들 반사 — 맞은 칸에 따라 수평 성분이 꺾인다 (법선 반사의 게임판 버전)
    const pyNow = padY();
    if (
      vyRef.current > 0 && byRef.current + 12 >= pyNow && byRef.current + 12 <= pyNow + PH &&
      bxRef.current + 12 > pxRef.current && bxRef.current < pxRef.current + PW
    ) {
      const off = (bxRef.current + 6 - (pxRef.current + PW / 2)) / (PW / 2);
      vxRef.current = SPEED * off * 0.9;
      vyRef.current = -Math.abs(vyRef.current);
      byRef.current = pyNow - 12;
    }
    // 벽돌 충돌 — 겹친 칸을 끄고 뚫은 변으로 반사한다
    const bricks = bricksRef.current;
    for (let i = 0; i < bricks.length; i++) {
      const b = bricks[i];
      if (!b.alive) continue;
      const bxx = scaled(BX + b.c * (BW + GAP));
      const byy = BY + b.r * (BH + GAP);
      if (bxRef.current + 12 > bxx && bxRef.current < bxx + scaled(BW) && byRef.current + 12 > byy && byRef.current < byy + BH) {
        b.alive = false;
        b.el.classList.add(styles.isHit);
        scoreRef.current += 1;
        setScore(scoreRef.current);
        const overX = bxRef.current + 6 - (bxx + scaled(BW) / 2);
        const overY = byRef.current + 6 - (byy + BH / 2);
        if (Math.abs(overX) > Math.abs(overY)) { vxRef.current = overX > 0 ? Math.abs(vxRef.current) : -Math.abs(vxRef.current); }
        else { vyRef.current = overY > 0 ? Math.abs(vyRef.current) : -Math.abs(vyRef.current); }
        break;
      }
    }
    // 공을 놓쳤으면 패들 위에 다시 얹는다
    if (byRef.current > h + 8) {
      stuckRef.current = true;
      bxRef.current = pxRef.current + PW / 2 - 6;
      byRef.current = padY() - 14;
    }
    paint();
    rafRef.current = requestAnimationFrame(step);
  }

  function wake(): void {
    setDemo(false);
    if (reduced()) {
      pxRef.current = 176;
      stuckRef.current = true;
      bxRef.current = pxRef.current + PW / 2 - 6;
      byRef.current = padY() - 14;
      paint();
      return;
    }
    if (!runningRef.current) {
      runningRef.current = true;
      lastRef.current = performance.now();
      rafRef.current = requestAnimationFrame(step);
    }
  }

  function movePaddle(x: number): void {
    const field = fieldRef.current;
    if (!field) return;
    pxRef.current = Math.max(0, Math.min(field.clientWidth - PW, x));
    if (!runningRef.current) wake();
  }

  function launchBall(): void {
    wake();
    stuckRef.current = false;
    vxRef.current = SPEED * 0.66;
    vyRef.current = -SPEED * 0.75;
  }

  function restart(): void {
    const bricks = bricksRef.current;
    for (let i = 0; i < bricks.length; i++) {
      bricks[i].alive = true;
      bricks[i].el.classList.remove(styles.isHit);
    }
    scoreRef.current = 0;
    setScore(0);
    stuckRef.current = true;
    pxRef.current = 176;
    wake();
  }

  useEffect(() => {
    const box = bricksBoxRef.current;
    if (box) {
      const nodes = box.querySelectorAll("i");
      const built: Brick[] = [];
      for (let n = 0; n < nodes.length; n++) {
        built.push({ el: nodes[n], r: CELLS[n].r, c: CELLS[n].c, alive: true });
      }
      bricksRef.current = built;
    }
    laid();
    paint();
    function onResize(): void { laid(); }
    window.addEventListener("resize", onResize);
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  function onPointerMove(event: ReactPointerEvent<HTMLDivElement>): void {
    const field = fieldRef.current;
    if (!field) return;
    const r = field.getBoundingClientRect();
    movePaddle(event.clientX - r.left - PW / 2);
  }

  function onKeyDown(event: KeyEvt): void {
    if (event.key === "ArrowLeft") movePaddle(pxRef.current - JUMP);
    else if (event.key === "ArrowRight") movePaddle(pxRef.current + JUMP);
    else if (event.key === "Enter" || event.key === " ") { event.preventDefault(); launchBall(); }
    else return;
    event.preventDefault();
  }

  const cls = [styles.root, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  function brickCls(r: number, c: number): string {
    const spot = styles["brickR" + r + "C" + c] || "";
    return [styles.brick, styles["brickR" + r] || "", spot].filter(Boolean).join(" ");
  }
  return (
    <main className={styles.stage}>
      <svg width="0" height="0" style={{ position: "absolute" }} aria-hidden="true">
        <defs>
          <symbol id="ico-ball" viewBox="0 0 256 256" fill="currentColor"><g><path d="M224 128a96 96 0 1 1-96-96a96 96 0 0 1 96 96" opacity=".2"/><path d="M128 24a104 104 0 1 0 104 104A104.11 104.11 0 0 0 128 24m0 192a88 88 0 1 1 88-88a88.1 88.1 0 0 1-88 88"/></g></symbol>
          <symbol id="ico-reset" viewBox="0 0 256 256" fill="currentColor"><g><path d="M232 136a104 104 0 1 1-38.17-80.55L208 60v-4a8 8 0 0 1 16 0v34a8 8 0 0 1-8 8h-34a8 8 0 0 1 0-16h7.6l-8.89-7.4A88 88 0 1 0 216 136a8 8 0 0 1 16 0Z" opacity=".2"/><path d="M232 136a104 104 0 1 1-38.17-80.55L208 60v-4a8 8 0 0 1 16 0v34a8 8 0 0 1-8 8h-34a8 8 0 0 1 0-16h7.6l-8.89-7.4A88 88 0 1 0 216 136a8 8 0 0 1 16 0Z"/></g></symbol>
        </defs>
      </svg>
      <div className={cls} style={vars}>
        <p className={styles.hint}>
          <svg className={styles.ico} aria-hidden="true"><use href="#ico-ball" /></svg>
          <span>패들이 마우스를 따라오고 공은 벽돌에 부딪힌 만큼 점수가 오릅니다</span>
        </p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onPointerMove={onPointerMove}
          onKeyDown={onKeyDown}
        >
          <p className={styles.score} aria-live="polite">
            <span className={styles.scoreVal}>{SCORE_LABEL} {score}</span>
            <span className={styles.scoreLoop} aria-hidden="true"><i>점수 0</i><i>점수 1</i><i>점수 2</i></span>
          </p>
          <div className={styles.bricks} ref={bricksBoxRef} aria-hidden="true">
            {CELLS.map((cell) => (
              <i key={`${cell.r}-${cell.c}`} className={brickCls(cell.r, cell.c)} />
            ))}
          </div>
          <span className={styles.ball} ref={ballRef} aria-hidden="true"></span>
          <span className={styles.paddle} ref={paddleRef} aria-hidden="true"></span>
        </div>
        <div className={styles.bar}>
          <button className={styles.launch} type="button" onClick={launchBall}>
            <svg className={styles.ico} aria-hidden="true"><use href="#ico-ball" /></svg><span>공 놓기</span>
          </button>
          <button className={styles.reset} type="button" onClick={restart}>
            <svg className={styles.ico} aria-hidden="true"><use href="#ico-reset" /></svg><span>처음으로</span>
          </button>
        </div>
      </div>
    </main>
  );
}