:root {
  color-scheme: light dark;
  --bg-gradient: linear-gradient(145deg, #022c22, #0f766e 45%, #064e3b 85%);
  --surface: rgba(3, 30, 21, 0.78);
  --surface-strong: rgba(4, 47, 35, 0.92);
  --surface-muted: rgba(255, 255, 255, 0.08);
  --border: rgba(148, 213, 189, 0.18);
  --text-primary: #f4fdf9;
  --text-secondary: rgba(228, 255, 244, 0.72);
  --accent: #34d399;
  --accent-strong: #10b981;
  --danger: #f43f5e;
  --success: #22c55e;
  --shadow: 0 22px 45px rgba(2, 44, 34, 0.5);
  --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, 44px);
}

.c4-app {
  width: min(1100px, 100%);
  min-height: 92vh;
  backdrop-filter: blur(20px) saturate(145%);
  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(52, 211, 153, 0.25), rgba(2, 44, 34, 0.9));
}

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

.branding .icon {
  display: grid;
  place-items: center;
  width: clamp(52px, 6vw, 68px);
  height: clamp(52px, 6vw, 68px);
  border-radius: 50%;
  background: rgba(15, 118, 110, 0.35);
  font-size: clamp(26px, 4vw, 36px);
  color: var(--accent);
  filter: drop-shadow(0 10px 22px rgba(16, 185, 129, 0.35));
}

.branding h1 {
  margin: 0;
  font-size: clamp(24px, 5vw, 34px);
  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: 6px;
  padding: 6px 12px;
  border-radius: 999px;
  background: var(--surface-muted);
  border: 1px solid var(--border);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.connection-indicator .dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px rgba(16, 185, 129, 0.55);
}

.connection-indicator[data-state="connected"] .dot {
  background: var(--success);
  box-shadow: 0 0 10px rgba(34, 197, 94, 0.6);
}

.connection-indicator[data-state="error"] .dot {
  background: var(--danger);
  box-shadow: 0 0 10px rgba(244, 63, 94, 0.6);
}

.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(280px, 1fr));
  justify-content: center;
  justify-items: center;
}

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

.card {
  background: rgba(4, 47, 35, 0.78);
  border: 1px solid rgba(148, 213, 189, 0.12);
  border-radius: var(--radius-md);
  padding: clamp(18px, 3vw, 28px);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.06);
  width: min(420px, 100%);
}

.card--accent {
  background: linear-gradient(145deg, rgba(52, 211, 153, 0.3), rgba(2, 44, 34, 0.92));
  border-color: rgba(52, 211, 153, 0.38);
}

.card--join {
  max-width: 380px;
  padding: clamp(16px, 2.8vw, 22px);
}

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

.card--info {
  background: rgba(8, 15, 30, 0.72);
}

.card h2,
.card h3 {
  margin: 0 0 12px;
  font-size: clamp(20px, 3vw, 24px);
}

.card p {
  margin: 0 0 12px;
  color: var(--text-secondary);
  line-height: 1.45;
  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(52, 211, 153, 0.25);
}

.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, #34d399, #10b981);
  color: #022c22;
  box-shadow: 0 14px 30px rgba(16, 185, 129, 0.35);
}

.btn--primary:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 18px 40px rgba(16, 185, 129, 0.5);
}

.btn--ghost {
  background: rgba(148, 213, 189, 0.12);
  color: var(--text-primary);
  border: 1px solid rgba(148, 213, 189, 0.24);
}

.btn--ghost:hover:not(:disabled) {
  transform: translateY(-1px);
  background: rgba(148, 213, 189, 0.22);
}

.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(4, 47, 35, 0.82);
  border: 1px solid rgba(148, 213, 189, 0.16);
  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(16, 185, 129, 0.22);
  border-radius: 999px;
  padding: 8px 16px;
  border: 1px solid rgba(16, 185, 129, 0.42);
}

.countdown[data-critical="true"] {
  background: rgba(244, 63, 94, 0.24);
  border-color: rgba(244, 63, 94, 0.65);
}

.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: 14px;
  min-height: 0;
}

.column-controls {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: clamp(8px, 1.8vw, 16px);
  padding: 0 clamp(12px, 3vw, 20px);
}

.column-button {
  border: 1px solid rgba(52, 211, 153, 0.5);
  background: rgba(52, 211, 153, 0.18);
  color: var(--accent);
  font-size: clamp(18px, 3vw, 24px);
  border-radius: var(--radius-sm);
  padding: 8px 0;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition);
}

.column-button:hover:not(:disabled) {
  background: rgba(52, 211, 153, 0.35);
  transform: translateY(-2px);
  box-shadow: 0 10px 20px rgba(16, 185, 129, 0.22);
}

.column-button:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.board {
  position: relative;
  width: 100%;
  max-width: min(720px, 100%);
  aspect-ratio: calc(7 / 6);
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  grid-template-rows: repeat(6, 1fr);
  grid-auto-rows: 1fr;
  gap: clamp(8px, 1.6vw, 16px);
  padding: clamp(18px, 3.8vw, 28px);
  background: linear-gradient(160deg, rgba(16, 185, 129, 0.75), rgba(5, 150, 105, 0.95));
  border-radius: var(--radius-lg);
  border: 1px solid rgba(148, 213, 189, 0.16);
  box-shadow: inset 0 18px 28px rgba(2, 44, 34, 0.5);
  margin: 0 auto;
}

.board::after {
  content: "";
  position: absolute;
  inset: clamp(10px, 2vw, 18px);
  border-radius: calc(var(--radius-lg) - 10px);
  border: 1px solid rgba(255, 255, 255, 0.08);
  pointer-events: none;
}

.board-cell {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  aspect-ratio: 1;
  min-width: 0;
  min-height: 0;
  padding: 0;
  background: rgba(6, 95, 70, 0.9);
  border: 1px solid rgba(148, 213, 189, 0.26);
  border-radius: 50%;
  cursor: pointer;
  overflow: hidden;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.board-cell[data-mark="R"],
.board-cell[data-mark="Y"] {
  border-color: transparent;
}

.board-cell:hover:not(:disabled) {
  transform: translateY(-4px);
  box-shadow: 0 12px 22px rgba(52, 211, 153, 0.22);
  border-color: rgba(148, 213, 189, 0.36);
}

.board-cell:disabled {
  cursor: default;
  transform: none;
  box-shadow: none;
}

.board-cell[data-winning="true"] {
  border-color: rgba(52, 211, 153, 0.6);
  box-shadow: 0 0 0 3px rgba(52, 211, 153, 0.35), 0 14px 24px rgba(16, 185, 129, 0.35);
}

.board-cell .mark {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  z-index: 1;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  font-size: clamp(28px, 6vw, 48px);
  font-weight: 700;
  color: transparent;
  background: transparent;
  border: none;
  box-sizing: border-box;
  transition: transform var(--transition), background var(--transition), box-shadow var(--transition);
}

.board-cell[data-mark="R"] .mark {
  background: transparent;
}

.board-cell[data-mark="Y"] .mark {
  background: transparent;
}

.board-cell[data-winning="true"] .mark {
  transform: scale(1.05);
  box-shadow: 0 12px 24px rgba(16, 185, 129, 0.42);
}

.board-cell[data-mark="R"] {
  background: #dc2626;
  box-shadow: 0 8px 16px rgba(220, 38, 38, 0.4);
}

.board-cell[data-mark="Y"] {
  background: #f59e0b;
  box-shadow: 0 8px 16px rgba(245, 158, 11, 0.35);
}

.turn-indicator {
  text-align: center;
  font-size: 16px;
  padding: 14px 16px;
  border-radius: var(--radius-sm);
  background: rgba(148, 213, 189, 0.12);
  border: 1px solid rgba(148, 213, 189, 0.2);
}

.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(52, 211, 153, 0.28);
  color: var(--text-primary);
  transform: translateY(-1px);
  box-shadow: 0 10px 18px rgba(16, 185, 129, 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(16, 185, 129, 0.18);
  border: 1px solid rgba(16, 185, 129, 0.35);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

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

.badge--player-r {
  background: rgba(239, 68, 68, 0.18);
  border-color: rgba(239, 68, 68, 0.45);
  color: #fecaca;
}

.badge--player-y {
  background: rgba(250, 204, 21, 0.2);
  border-color: rgba(250, 204, 21, 0.45);
  color: #fef9c3;
}

.members .badge--host {
  background: rgba(34, 197, 94, 0.24);
  border-color: rgba(34, 197, 94, 0.55);
}

.app-footer {
  border-top: 1px solid var(--border);
  padding: 16px 24px;
  text-align: center;
  font-size: 14px;
  color: var(--text-secondary);
  background: rgba(3, 30, 21, 0.78);
}

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

@media (max-width: 920px) {
  .game-layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    order: -1;
  }

  .mobile-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 12px;
  }

  .board {
    max-width: min(640px, 100%);
  }
}

@media (max-width: 768px) {
  body {
    padding: 18px;
  }

  .c4-app {
    min-height: 100vh;
  }

  .app-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 18px;
  }

  .connection-indicator {
    width: 100%;
    justify-content: center;
  }

  .game-topbar {
    flex-direction: column;
    align-items: stretch;
    text-align: center;
  }

  .game-controls {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
  }

  .game-controls .btn {
    width: 100%;
  }

  .board {
    padding: clamp(14px, 5vw, 22px);
  }
}

@media (max-width: 560px) {
  body {
    padding: 12px;
  }

  .app-header {
    align-items: center;
    text-align: center;
  }

  .branding {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }

  .app-content {
    padding: clamp(16px, 6vw, 22px);
  }

  .panel--lobby {
    grid-template-columns: 1fr;
  }

  .column-controls {
    gap: 8px;
  }

  .column-button {
    font-size: 18px;
  }

  .board {
    gap: clamp(6px, 2vw, 12px);
    padding: clamp(12px, 4vw, 18px);
  }

  .board-cell .mark {
    width: 86%;
    height: 86%;
  }
}

@media (max-width: 420px) {
  body {
    padding: 10px;
  }

  .c4-app {
    border-radius: 22px;
  }

  .game-topbar,
  .card {
    padding: 14px;
  }

  .column-controls {
    padding: 0 4px;
  }

  .turn-indicator {
    font-size: 15px;
  }
}