:root {
  color-scheme: dark;
  --bg: #07111f;
  --bg-soft: #0e1a31;
  --panel: rgba(10, 16, 32, 0.78);
  --panel-strong: rgba(14, 22, 42, 0.95);
  --border: rgba(175, 195, 255, 0.16);
  --border-strong: rgba(175, 195, 255, 0.32);
  --text: #eff4ff;
  --text-soft: #a9b7d8;
  --accent: #8ce6d8;
  --accent-strong: #52d9c6;
  --x: #8db8ff;
  --o: #ffd66c;
  --win: #5ef0a7;
  --shadow: 0 30px 80px rgba(0, 0, 0, 0.35);
  --radius-xl: 32px;
  --radius-lg: 24px;
  --radius-md: 18px;
  --radius-sm: 14px;
  --space-1: 0.5rem;
  --space-2: 0.75rem;
  --space-3: 1rem;
  --space-4: 1.5rem;
  --space-5: 2rem;
  --space-6: 2.75rem;
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
}

body {
  margin: 0;
  min-height: 100dvh;
  font-family: "Segoe UI Variable", "Segoe UI", system-ui, sans-serif;
  background:
    radial-gradient(circle at top left, rgba(82, 217, 198, 0.18), transparent 34%),
    radial-gradient(circle at top right, rgba(141, 184, 255, 0.16), transparent 28%),
    linear-gradient(160deg, #060d18 0%, #0a1527 48%, #0c1830 100%);
  color: var(--text);
}

button,
input,
textarea,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

.page-shell {
  position: relative;
  min-height: 100dvh;
  padding: clamp(1rem, 2vw + 0.5rem, 2rem);
  overflow: hidden;
}

.page-shell::before,
.page-shell::after {
  content: "";
  position: absolute;
  inset: auto;
  width: min(44vw, 36rem);
  aspect-ratio: 1;
  border-radius: 50%;
  filter: blur(70px);
  opacity: 0.35;
  pointer-events: none;
}

.page-shell::before {
  top: -10rem;
  left: -10rem;
  background: rgba(82, 217, 198, 0.35);
}

.page-shell::after {
  right: -10rem;
  bottom: -10rem;
  background: rgba(141, 184, 255, 0.26);
}

.app-shell {
  position: relative;
  z-index: 1;
  max-width: 1180px;
  margin: 0 auto;
  display: grid;
  gap: var(--space-4);
}

.card {
  position: relative;
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.06), transparent 22%),
    var(--panel);
  box-shadow: var(--shadow);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  overflow: hidden;
  animation: rise 0.7s ease both;
}

.hero-card,
.game-card {
  padding: clamp(1.25rem, 2vw + 0.8rem, 2rem);
}

.game-card {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.04), transparent 18%),
    var(--panel-strong);
}

.eyebrow {
  margin: 0 0 0.75rem;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

h1,
h2,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0.75rem;
  font-size: clamp(2.4rem, 5vw, 4.8rem);
  line-height: 0.95;
  letter-spacing: -0.05em;
  max-width: 9ch;
}

h2 {
  margin-bottom: 0;
  font-size: clamp(1.35rem, 2vw, 2rem);
  letter-spacing: -0.03em;
}

.lede {
  max-width: 44rem;
  color: var(--text-soft);
  font-size: clamp(1rem, 1.5vw, 1.15rem);
  line-height: 1.65;
}

.status-grid {
  display: grid;
  gap: var(--space-3);
  margin-top: var(--space-4);
  grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr));
}

.status-tile,
.feature-card,
.status-banner {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: rgba(255, 255, 255, 0.045);
}

.status-tile {
  padding: 1rem 1.05rem;
}

.tile-label,
.status-label,
.feature-title {
  display: block;
  color: var(--text-soft);
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.tile-value {
  display: block;
  margin-top: 0.45rem;
  font-size: clamp(1.5rem, 2.7vw, 2.25rem);
  letter-spacing: -0.05em;
}

.feature-card {
  margin-top: var(--space-4);
  padding: 1rem 1.1rem 1.15rem;
}

.feature-title {
  margin-bottom: 0.9rem;
}

.feature-list {
  margin: 0;
  padding-left: 1.2rem;
  display: grid;
  gap: 0.7rem;
  color: var(--text-soft);
  line-height: 1.55;
}

.game-header {
  display: flex;
  gap: var(--space-3);
  align-items: start;
  justify-content: space-between;
  margin-bottom: var(--space-3);
}

.restart-button {
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  padding: 0.8rem 1.15rem;
  color: var(--text);
  background: linear-gradient(180deg, rgba(82, 217, 198, 0.18), rgba(82, 217, 198, 0.08));
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.08);
  transition:
    transform 160ms ease,
    border-color 160ms ease,
    background 160ms ease;
}

.restart-button:hover {
  transform: translateY(-1px);
  border-color: rgba(140, 230, 216, 0.55);
}

.restart-button:active {
  transform: translateY(0);
}

.restart-button:focus-visible,
.square:focus-visible {
  outline: 3px solid rgba(140, 230, 216, 0.8);
  outline-offset: 3px;
}

.status-banner {
  display: grid;
  gap: 0.4rem;
  padding: 1rem 1.05rem;
  margin-bottom: var(--space-4);
}

.status-message,
.board-hint {
  margin: 0;
  color: var(--text-soft);
  line-height: 1.55;
}

.board {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
}

.square {
  aspect-ratio: 1;
  display: grid;
  place-items: center;
  border: 1px solid rgba(178, 193, 230, 0.2);
  border-radius: var(--radius-md);
  background:
    radial-gradient(circle at top, rgba(255, 255, 255, 0.09), transparent 42%),
    rgba(255, 255, 255, 0.05);
  color: var(--text);
  font-size: clamp(2.5rem, 8vw, 4.5rem);
  font-weight: 800;
  letter-spacing: -0.08em;
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.1),
    0 18px 30px rgba(0, 0, 0, 0.18);
  transition:
    transform 160ms ease,
    border-color 160ms ease,
    background 160ms ease,
    box-shadow 160ms ease;
}

.square:hover:not(:disabled) {
  transform: translateY(-2px);
  border-color: rgba(140, 230, 216, 0.42);
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.14),
    0 20px 34px rgba(0, 0, 0, 0.26);
}

.square:disabled {
  cursor: default;
}

.square.is-x {
  color: var(--x);
}

.square.is-o {
  color: var(--o);
}

.square.is-winning {
  border-color: rgba(94, 240, 167, 0.85);
  background:
    radial-gradient(circle at top, rgba(94, 240, 167, 0.24), transparent 44%),
    rgba(94, 240, 167, 0.11);
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.18),
    0 0 0 1px rgba(94, 240, 167, 0.2),
    0 18px 38px rgba(0, 0, 0, 0.26);
}

.square.is-last-move {
  border-color: rgba(140, 230, 216, 0.5);
}

.board-hint {
  margin-top: var(--space-4);
}

@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(14px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (min-width: 760px) {
  .app-shell {
    gap: var(--space-5);
  }

  .hero-card,
  .game-card {
    padding: clamp(1.5rem, 2vw + 1rem, 2.5rem);
  }
}

@media (min-width: 980px) {
  .app-shell {
    grid-template-columns: minmax(0, 1.02fr) minmax(0, 0.98fr);
    align-items: start;
  }

  .hero-card {
    position: sticky;
    top: 1rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation: none !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}