:root {
  color-scheme: light dark;
  --bg-gradient: radial-gradient(circle at top left, #1f6feb, #0a2540 55%, #050b18 100%);
  --surface: rgba(15, 23, 42, 0.65);
  --surface-strong: rgba(15, 23, 42, 0.85);
  --surface-muted: rgba(255, 255, 255, 0.08);
  --border: rgba(255, 255, 255, 0.15);
  --text-primary: #f8fafc;
  --text-secondary: rgba(248, 250, 252, 0.72);
  --accent: #38bdf8;
  --accent-strong: #0ea5e9;
  --danger: #f43f5e;
  --success: #a3e635;
  --shadow: 0 22px 45px rgba(2, 6, 23, 0.55);
  --radius-lg: 28px;
  --radius-md: 18px;
  --radius-sm: 12px;
  --transition: 160ms ease-in-out;
  font-family: "Inter", "Segoe UI", Roboto, "Helvetica Neue", sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg-gradient);
  color: var(--text-primary);
  display: flex;
  align-items: stretch;
  justify-content: center;
  padding: clamp(16px, 4vw, 48px);
}

.ttt-app {
  width: min(1100px, 100%);
  min-height: 92vh;
  backdrop-filter: blur(20px) saturate(150%);
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  border-radius: var(--radius-lg);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: clamp(12px, 2vw, 32px);
  padding: clamp(20px, 4vw, 32px);
  border-bottom: 1px solid var(--border);
  background: linear-gradient(115deg, rgba(56, 189, 248, 0.25), rgba(15, 23, 42, 0.7));
}

.branding {
  display: flex;
  align-items: center;
  gap: 16px;
}

.branding .icon {
  display: grid;
  place-items: center;
  width: clamp(48px, 6vw, 64px);
  height: clamp(48px, 6vw, 64px);
  border-radius: 50%;
  background: rgba(15, 23, 42, 0.4);
  font-size: clamp(24px, 4vw, 32px);
  color: var(--accent);
  filter: drop-shadow(0 8px 18px rgba(14, 165, 233, 0.45));
}

.branding h1 {
  margin: 0;
  font-size: clamp(24px, 5vw, 32px);
  letter-spacing: 0.03em;
}

.branding p {
  margin: 4px 0 0;
  color: var(--text-secondary);
  font-size: clamp(14px, 2.5vw, 16px);
}

.connection-indicator {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 10px 18px;
  border-radius: 999px;
  background: var(--surface-muted);
  border: 1px solid var(--border);
  font-size: 14px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.connection-indicator .dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: #f97316;
  box-shadow: 0 0 12px rgba(249, 115, 22, 0.6);
}

.connection-indicator[data-state="connected"] .dot {
  background: var(--success);
  box-shadow: 0 0 14px rgba(163, 230, 53, 0.7);
}

.connection-indicator[data-state="error"] .dot {
  background: var(--danger);
  box-shadow: 0 0 14px rgba(244, 63, 94, 0.7);
}

.app-content {
  flex: 1 1 auto;
  display: flex;
  flex-direction: column;
  gap: clamp(16px, 3vw, 28px);
  padding: clamp(20px, 4vw, 32px);
  min-height: 0;
}

.panel {
  display: grid;
  gap: clamp(16px, 3vw, 24px);
}

.panel--lobby {
  grid-template-columns: repeat(auto-fit, minmax(min(280px, 100%), 1fr));
}

.panel--game {
  display: flex;
  flex-direction: column;
  gap: clamp(16px, 3vw, 24px);
  flex: 1 1 auto;
  min-height: 0;
}

.card {
  background: rgba(10, 17, 36, 0.76);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-md);
  padding: clamp(18px, 3vw, 28px);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.06);
}

.card--accent {
  background: linear-gradient(145deg, rgba(56, 189, 248, 0.28), rgba(10, 17, 36, 0.9));
  border-color: rgba(56, 189, 248, 0.35);
}

.card--join {
  max-width: 430px;
  padding: clamp(16px, 2.8vw, 22px);
  align-self: start;
}

.card--join h2 {
  margin-bottom: 10px;
}

.card--join .form-join {
  gap: 10px;
}

.card--join .input {
  padding: 10px 12px;
  font-size: 15px;
  letter-spacing: 0.06em;
}

.card--join .btn--primary {
  padding: 10px 16px;
}

.card--info {
  background: rgba(8, 15, 30, 0.7);
}

.card h2,
.card h3 {
  margin: 0 0 12px;
  font-size: clamp(20px, 3vw, 22px);
}

.card p {
  margin: 0 0 12px;
  color: var(--text-secondary);
  line-height: 1.4;
  font-size: 15px;
}

.room-code {
  font-family: "Fira Mono", "SFMono-Regular", ui-monospace, monospace;
  font-size: clamp(20px, 4vw, 24px);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
}

.share-links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin: 12px 0;
}

.form-join {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.input {
  flex: 1 1 180px;
  min-width: 0;
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(255, 255, 255, 0.16);
  background: rgba(15, 23, 42, 0.55);
  color: var(--text-primary);
  font-size: 16px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 4px rgba(56, 189, 248, 0.22);
}

.btn {
  border: none;
  cursor: pointer;
  border-radius: var(--radius-sm);
  padding: 12px 18px;
  font-weight: 600;
  letter-spacing: 0.04em;
  font-size: 15px;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition);
}

.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
}

.btn--primary {
  background: linear-gradient(120deg, #38bdf8, #0ea5e9);
  color: #041021;
  box-shadow: 0 15px 35px rgba(14, 165, 233, 0.35);
}

.btn--primary:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 18px 40px rgba(14, 165, 233, 0.5);
}

.btn--ghost {
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-primary);
  border: 1px solid rgba(255, 255, 255, 0.18);
}

.btn--ghost:hover:not(:disabled) {
  transform: translateY(-1px);
  background: rgba(255, 255, 255, 0.16);
}

.btn--danger {
  background: rgba(244, 63, 94, 0.18);
  color: var(--text-primary);
  border: 1px solid rgba(244, 63, 94, 0.55);
  box-shadow: 0 14px 28px rgba(244, 63, 94, 0.25);
}

.btn--danger:hover:not(:disabled) {
  transform: translateY(-2px);
  background: rgba(244, 63, 94, 0.26);
  box-shadow: 0 18px 38px rgba(244, 63, 94, 0.35);
}

.hint {
  font-size: 13px;
  color: rgba(248, 250, 252, 0.6);
}

.game-topbar {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: center;
  justify-content: space-between;
  background: rgba(15, 23, 42, 0.7);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-md);
  padding: 16px 20px;
}

.countdown {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: "Fira Mono", "SFMono-Regular", ui-monospace, monospace;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  background: rgba(8, 145, 178, 0.2);
  border-radius: 999px;
  padding: 8px 16px;
  border: 1px solid rgba(56, 189, 248, 0.4);
}

.countdown[data-critical="true"] {
  background: rgba(244, 63, 94, 0.18);
  border-color: rgba(244, 63, 94, 0.6);
}

.game-status {
  font-size: clamp(16px, 3vw, 18px);
  font-weight: 600;
  flex: 1 1 auto;
  text-align: center;
}

.game-controls {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  width: 100%;
}

.game-controls .btn {
  flex: 1 1 0;
  min-width: 0;
}

.game-layout {
  display: grid;
  grid-template-columns: minmax(0, 2fr) minmax(260px, 1fr);
  gap: clamp(18px, 4vw, 28px);
  flex: 1 1 auto;
}

.board-wrapper {
  display: flex;
  flex-direction: column;
  gap: 18px;
  min-height: 0;
}

.board {
  position: relative;
  width: 100%;
  aspect-ratio: 1;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  grid-auto-rows: 1fr;
  gap: clamp(12px, 2vw, 18px);
  padding: clamp(18px, 4vw, 24px);
  background: rgba(8, 15, 30, 0.45);
  border-radius: var(--radius-lg);
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: inset 0 12px 24px rgba(2, 6, 23, 0.4);
}

.board-cell {
  display: grid;
  place-items: center;
  min-width: 0;
  min-height: 0;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: clamp(18px, 3vw, 24px);
  color: var(--text-primary);
  font-size: clamp(42px, 8vw, 72px);
  font-weight: 700;
  cursor: pointer;
  transition: transform var(--transition), background var(--transition), border-color var(--transition);
}

.board-cell:hover:not(:disabled) {
  transform: translateY(-4px);
  background: rgba(56, 189, 248, 0.16);
  border-color: rgba(56, 189, 248, 0.5);
}

.board-cell:disabled {
  cursor: default;
  opacity: 0.9;
  transform: none;
}

.board-cell .mark {
  filter: drop-shadow(0 8px 18px rgba(14, 165, 233, 0.4));
}

.board-cell[data-mark="X"] .mark {
  color: #facc15;
}

.board-cell[data-mark="O"] .mark {
  color: #a855f7;
}

.board-cell[data-winning="true"] {
  background: rgba(163, 230, 53, 0.16);
  border-color: rgba(163, 230, 53, 0.65);
  box-shadow: 0 12px 25px rgba(163, 230, 53, 0.25);
}

.turn-indicator {
  text-align: center;
  font-size: 16px;
  padding: 14px 16px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.12);
}

.sidebar {
  display: grid;
  gap: 16px;
}

.mobile-tabs {
  display: none;
}

.mobile-tab {
  flex: 1 1 auto;
  border: none;
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  background: rgba(15, 23, 42, 0.6);
  color: var(--text-secondary);
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), transform var(--transition);
}

.mobile-tab.is-active {
  background: rgba(56, 189, 248, 0.22);
  color: var(--text-primary);
  transform: translateY(-1px);
  box-shadow: 0 10px 18px rgba(14, 165, 233, 0.25);
}

.mobile-tab:not(.is-active):hover {
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-primary);
}

.history {
  margin: 0;
  padding-left: 18px;
  display: grid;
  gap: 8px;
}

.history li {
  font-size: 14px;
  color: var(--text-secondary);
}

.members {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 8px;
}

.members li {
  display: flex;
  justify-content: space-between;
  font-size: 14px;
  color: var(--text-secondary);
}

.members .badge {
  padding: 4px 10px;
  border-radius: 999px;
  background: rgba(56, 189, 248, 0.2);
  border: 1px solid rgba(56, 189, 248, 0.35);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.members .badge-wrap {
  display: flex;
  gap: 6px;
}

.members .badge--host {
  background: rgba(250, 204, 21, 0.2);
  border-color: rgba(250, 204, 21, 0.45);
}

.app-footer {
  border-top: 1px solid var(--border);
  padding: 16px 24px;
  font-size: 13px;
  color: rgba(248, 250, 252, 0.55);
  text-align: center;
  background: rgba(10, 17, 36, 0.75);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 960px) {
  .game-layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  body {
    padding: 12px;
    align-items: stretch;
    justify-content: stretch;
  }

  .ttt-app {
    border-radius: 20px;
    min-height: 100vh;
  }

  .app-header {
    flex-direction: column;
    align-items: stretch;
    text-align: center;
    padding: 18px;
  }

  .app-header .branding p {
    display: none;
  }

  .connection-indicator {
    align-self: flex-end;
    width: auto;
    justify-content: flex-end;
  }

  .board {
    padding: 16px;
  }
}

@media (max-width: 640px) {
  body {
    padding: 0;
    justify-content: stretch;
  }

  .ttt-app {
    border-radius: 0;
    min-height: 100vh;
  }

  .app-content {
    padding: 16px 16px 20px;
    gap: 18px;
  }

  .panel--lobby {
    gap: 16px;
  }

  .panel--game {
    gap: 16px;
    flex: 1 1 auto;
  }

  .card--join {
    max-width: 100%;
    padding: 14px 16px;
  }

  .card--join .input {
    padding: 9px 12px;
    font-size: 14.5px;
    letter-spacing: 0.05em;
  }

  .card--join .btn--primary {
    padding: 9px 14px;
  }

  .card--join p {
    font-size: 14px;
    margin-bottom: 10px;
  }

  .card--join .form-join {
    gap: 8px;
  }

  .branding h1 {
    font-size: 20px;
  }

  .connection-indicator {
    align-self: flex-end;
    padding: 6px 12px;
    font-size: 11px;
    letter-spacing: 0.05em;
    gap: 6px;
  }

  .connection-indicator .dot {
    width: 9px;
    height: 9px;
  }

  .game-topbar {
    flex-direction: row;
    flex-wrap: wrap;
    align-items: center;
    text-align: left;
    gap: 12px;
    padding: 14px;
    justify-content: space-between;
  }

  .countdown {
    padding: 6px 14px;
    font-size: 13px;
    letter-spacing: 0.06em;
  }

  .game-status {
    font-size: 15px;
    text-align: left;
  }

  .game-controls {
    width: 100%;
    justify-content: space-between;
    gap: 8px;
    flex-wrap: nowrap;
  }

  .game-controls .btn {
    flex: 1 1 0;
    min-width: 0;
  }

  .game-layout {
    display: flex;
    flex-direction: column;
    gap: 14px;
    flex: 1 1 auto;
  }

  .board-wrapper {
    order: 1;
    flex: 1 1 auto;
  }

  .sidebar {
    order: 2;
    display: grid;
    gap: 0;
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-md);
    background: rgba(10, 17, 36, 0.65);
  }

  .mobile-tabs {
    display: flex;
    gap: 8px;
    padding: 10px;
  }

  .sidebar .card {
    padding: 16px;
  }

  .sidebar .card[data-panel] {
    display: none;
  }

  .sidebar[data-active-panel="info"] .card[data-panel="info"],
  .sidebar[data-active-panel="history"] .card[data-panel="history"],
  .sidebar[data-active-panel="members"] .card[data-panel="members"] {
    display: block;
  }

  .sidebar .card h3 {
    display: none;
  }

  .board {
    padding: 12px;
    gap: 10px;
    max-height: 58vh;
    align-self: center;
  }

  .board-cell {
    border-radius: 18px;
    font-size: clamp(32px, 15vw, 48px);
  }

  .turn-indicator {
    font-size: 14px;
  }

  .history,
  .members {
    max-height: 180px;
    overflow-y: auto;
  }
}

@media (max-width: 520px) {
  .game-topbar {
    align-items: center;
    gap: 8px;
    justify-content: space-between;
  }

  .countdown {
    justify-content: center;
    text-align: left;
  }

  .game-controls {
    width: 100%;
    flex-wrap: wrap;
    align-items: center;
    gap: 8px;
  }

  .game-controls .btn {
    flex: 1 1 calc(50% - 8px);
    min-width: 0;
  }

  .board {
    padding: 10px;
    gap: 8px;
    max-height: 54vh;
  }

  .card {
    padding: 12px;
  }

  .history li,
  .members li {
    font-size: 13px;
  }

  .app-footer {
    display: none;
  }

  .form-join {
    flex-direction: column;
  }

  .input {
    width: 100%;
  }
}

@media (max-width: 420px) {
  body {
    padding: 0;
  }

  .branding {
    flex-direction: column;
    align-items: center;
    gap: 12px;
  }

  .branding h1 {
    font-size: 20px;
  }

  .branding p {
    font-size: 14px;
  }

  .app-header {
    gap: 14px;
    padding: 14px;
  }

  .card {
    padding: 12px;
  }

  .btn {
    padding: 10px 14px;
  }

  .turn-indicator {
    font-size: 13px;
  }

  .mobile-tabs {
    padding: 6px;
    gap: 6px;
  }

  .board {
    max-height: 48vh;
  }

  .connection-indicator {
    font-size: 10px;
    padding: 5px 10px;
    gap: 5px;
  }

  .card--join .input {
    font-size: 14px;
    padding: 8px 11px;
  }

  .app-footer {
    padding: 10px 12px;
    font-size: 11px;
    display: none;
  }
}