:root {
  --bg: #07070f;
  --surface: #11111f;
  --surface-2: #1a1a2e;
  --line: #2a2a45;
  --ink: #ecebff;
  --muted: #9a98c3;
  --neon: #22e3ff;
  --pink: #ff3ec8;
  --lime: #b6ff3b;
  /* Chừa chỗ cho tiêu đề và dòng kết quả để khung game không phải cuộn */
  --size: min(92vw, calc(100vh - 170px), 480px);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  height: 100%;
  background: var(--bg);
  color: var(--ink);
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  -webkit-user-select: none;
  user-select: none;
  overscroll-behavior: none;
  scrollbar-width: thin;
  scrollbar-color: var(--line) var(--bg);
  color-scheme: dark;
}

.app {
  width: var(--size);
  margin: 0 auto;
  padding: 14px 0 10px;
}

.top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
}

.title {
  margin: 0;
  font-size: clamp(28px, 8vmin, 44px);
  font-weight: 800;
  letter-spacing: 1px;
  background: linear-gradient(90deg, var(--neon), var(--pink));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.scores {
  display: flex;
  gap: 8px;
}

.box {
  min-width: 72px;
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--surface);
  text-align: center;
}

.label {
  display: block;
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.value {
  display: block;
  font-size: 20px;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.btn {
  padding: 10px 20px;
  border: 0;
  border-radius: 10px;
  background: linear-gradient(90deg, var(--neon), var(--pink));
  color: var(--bg);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}

.btn.ghost {
  border: 1px solid var(--line);
  background: transparent;
  color: var(--ink);
}

.stage {
  position: relative;
  width: var(--size);
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  background: var(--surface);
  touch-action: none;
}

canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.overlay {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 20px;
  background: rgb(7 7 15 / 0.78);
  backdrop-filter: blur(3px);
  text-align: center;
}

.overlay-title {
  margin: 0;
  font-size: clamp(24px, 7vmin, 36px);
  font-weight: 800;
}

.overlay-text {
  margin: 0 0 10px;
  color: var(--muted);
}

.result {
  margin: 12px 0 0;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: var(--surface);
  font-size: 13px;
  text-align: center;
}

.result.ok {
  border-color: rgb(182 255 59 / 0.5);
  color: var(--lime);
}

.result.err {
  border-color: rgb(255 62 200 / 0.5);
  color: var(--pink);
}

.note {
  margin: 12px 0 0;
  font-size: 12px;
  color: var(--muted);
  text-align: center;
}

.hidden {
  display: none !important;
}

/* Memory: lưới thẻ 4 x 4 */
.box {
  min-width: 64px;
  padding: 6px 8px;
}

.value {
  font-size: 17px;
}

.bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 12px;
}

.hint {
  margin: 0;
  font-size: 13px;
  color: var(--muted);
}

.btn.ghost {
  padding: 8px 14px;
  white-space: nowrap;
}

.stage {
  aspect-ratio: 1 / 1;
  padding: clamp(6px, 2vmin, 12px);
  touch-action: manipulation;
}

.grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(4, 1fr);
  gap: clamp(6px, 2vmin, 12px);
  height: 100%;
}

.card {
  padding: 0;
  border: 0;
  background: transparent;
  perspective: 600px;
  cursor: pointer;
}

.inner {
  position: relative;
  display: block;
  width: 100%;
  height: 100%;
  transition: transform 0.28s ease;
  transform-style: preserve-3d;
}

.card.up .inner {
  transform: rotateY(180deg);
}

.face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: 10px;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}

.back {
  border: 1px solid var(--line);
  background:
    radial-gradient(circle at 30% 30%, rgb(34 227 255 / 0.25), transparent 60%),
    radial-gradient(circle at 70% 70%, rgb(255 62 200 / 0.25), transparent 60%),
    var(--surface-2);
}

.card:hover .back {
  border-color: var(--neon);
}

.front {
  transform: rotateY(180deg);
  border: 1px solid var(--neon);
  background: var(--surface-2);
  font-size: clamp(26px, 9vmin, 48px);
}

.card.matched .front {
  border-color: var(--lime);
  box-shadow: 0 0 14px rgb(182 255 59 / 0.45);
}

.card:focus-visible {
  outline: 2px solid var(--neon);
  outline-offset: 2px;
  border-radius: 10px;
}

:root {
  --size: min(92vw, calc(100vh - 215px), 480px);
}