* { margin: 0; padding: 0; box-sizing: border-box; }
:root {
  --primary: #6366f1;
  --primary-hover: #4f46e5;
  --primary-gradient: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
  --primary-glow: rgba(99, 102, 241, 0.35);
  --bg: linear-gradient(160deg, #dbeafe 0%, #e8e0ff 35%, #fce7f3 70%, #fef3c7 100%);
  --card: rgba(255, 255, 255, 0.72);
  --card-hover: rgba(255, 255, 255, 0.85);
  --card-border: rgba(255, 255, 255, 0.55);
  --text: #1e293b;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  --border: rgba(148, 163, 184, 0.25);
  --danger: #ef4444;
  --success: #22c55e;
  --warning: #f59e0b;
  --shadow: 0 8px 32px rgba(0,0,0,0.06);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.1);
  --radius: 22px;
  --radius-sm: 14px;
  --red-piece: #c0392b;
  --dark-piece: #2c3e50;
}
html, body {
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif;
  background: var(--bg);
  background-attachment: fixed;
  color: var(--text);
  overflow: hidden;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
}
#app { height: 100%; position: relative; }

.bg-shapes { position: fixed; inset: 0; pointer-events: none; z-index: 0; overflow: hidden; }
.shape { position: absolute; border-radius: 50%; filter: blur(80px); opacity: 0.45; animation: float 20s ease-in-out infinite; }
.shape-1 { width: 300px; height: 300px; background: #fca5a5; top: -80px; right: -60px; }
.shape-2 { width: 250px; height: 250px; background: #c4b5fd; bottom: 10%; left: -80px; animation-delay: -7s; }
.shape-3 { width: 200px; height: 200px; background: #fde68a; bottom: -50px; right: 20%; animation-delay: -14s; }
@keyframes float {
  0%,100% { transform: translateY(0) scale(1); }
  33% { transform: translateY(-25px) scale(1.05); }
  66% { transform: translateY(15px) scale(0.95); }
}

.screen {
  position: absolute; inset: 0; display: flex; align-items: center; justify-content: center;
  padding: 20px; opacity: 0; pointer-events: none;
  transition: opacity 0.4s ease, transform 0.4s ease; transform: scale(0.97); z-index: 1;
}
.screen.active { opacity: 1; pointer-events: auto; transform: scale(1); }

.card {
  background: var(--card); backdrop-filter: blur(24px); -webkit-backdrop-filter: blur(24px);
  border: 1px solid var(--card-border); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 44px 34px; width: 100%; max-width: 390px; text-align: center;
}

.logo { margin-bottom: 36px; }
.logo h1 {
  font-size: 36px; font-weight: 800; letter-spacing: 6px; margin-top: 16px;
  background: linear-gradient(135deg, var(--red-piece) 0%, #e74c3c 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.logo .subtitle { color: var(--text-muted); font-size: 13px; margin-top: 8px; letter-spacing: 10px; font-weight: 500; }
.logo-pieces { display: flex; justify-content: center; gap: 14px; }
.logo-piece {
  width: 52px; height: 52px; border-radius: 50%; display: inline-flex; align-items: center; justify-content: center;
  font-size: 24px; font-weight: 700;
  font-family: "KaiTi","STKaiti","楷体","SimSun","Noto Serif SC",serif;
  box-shadow: 2px 3px 12px rgba(0,0,0,0.2), inset 0 -2px 4px rgba(0,0,0,0.08);
  transition: transform 0.3s ease; position: relative;
}
.logo-piece:hover { transform: scale(1.12); }
.logo-piece.red {
  background: radial-gradient(circle at 35% 35%, #fff5ee, #f0c8a8 60%, #d4956b);
  border: 2.5px solid #8b2500; color: #8b1a1a;
}
.logo-piece.dark {
  background: radial-gradient(circle at 35% 35%, #f0f0f0, #b0b8c4 60%, #6b7a8d);
  border: 2.5px solid #3a4a5c; color: #1a2a3a;
}

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 15px 28px; border: none; border-radius: var(--radius-sm);
  font-size: 16px; font-weight: 600; cursor: pointer;
  transition: all 0.25s ease; outline: none; -webkit-tap-highlight-color: transparent; position: relative;
}
.btn:active { transform: scale(0.96); }
.btn-primary {
  background: var(--primary-gradient); color: white; width: 100%;
  box-shadow: 0 4px 18px var(--primary-glow); letter-spacing: 2px;
}
.btn-primary:hover { box-shadow: 0 8px 28px rgba(99,102,241,0.5); transform: translateY(-1px); }
.btn-accent { background: var(--primary-gradient); color: white; width: 100%; box-shadow: 0 4px 14px var(--primary-glow); }
.btn-ghost {
  background: rgba(255,255,255,0.6); color: var(--primary); border: 1px solid var(--border); width: 100%;
  backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px);
}
.btn-ghost:hover { background: rgba(255,255,255,0.85); border-color: var(--primary); }
.btn-outline {
  background: rgba(255,255,255,0.5); color: var(--text); border: 1.5px solid var(--border);
  padding: 10px 24px; font-size: 14px; backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px);
}
.btn-outline:hover { background: rgba(255,255,255,0.8); }
.btn-danger-outline { color: var(--danger); border-color: rgba(239,68,68,0.25); }
.btn-danger-outline:hover { background: rgba(254,242,242,0.7); }

.home-actions { display: flex; flex-direction: column; gap: 14px; }
.mode-section { display: flex; flex-direction: column; gap: 10px; }
.mode-label { font-size: 13px; font-weight: 600; color: var(--text-muted); letter-spacing: 2px; text-align: left; }
.ai-levels { display: flex; gap: 10px; }
.btn-ai {
  flex: 1; padding: 14px 0; border-radius: var(--radius-sm); font-size: 15px; font-weight: 700;
  letter-spacing: 2px; color: white; border: none; transition: all 0.25s ease;
}
.btn-ai:active { transform: scale(0.95); }
#btn-ai-easy { background: linear-gradient(135deg,#34d399,#10b981); box-shadow: 0 4px 14px rgba(16,185,129,0.3); }
#btn-ai-easy:hover { box-shadow: 0 6px 22px rgba(16,185,129,0.45); transform: translateY(-1px); }
#btn-ai-medium { background: linear-gradient(135deg,#fbbf24,#f59e0b); box-shadow: 0 4px 14px rgba(245,158,11,0.3); }
#btn-ai-medium:hover { box-shadow: 0 6px 22px rgba(245,158,11,0.45); transform: translateY(-1px); }
#btn-ai-hard { background: linear-gradient(135deg,#f87171,#ef4444); box-shadow: 0 4px 14px rgba(239,68,68,0.3); }
#btn-ai-hard:hover { box-shadow: 0 6px 22px rgba(239,68,68,0.45); transform: translateY(-1px); }

.divider { display: flex; align-items: center; gap: 14px; color: var(--text-light); font-size: 13px; font-weight: 500; }
.divider::before, .divider::after { content: ""; flex: 1; height: 1px; background: linear-gradient(90deg,transparent,var(--border),transparent); }
.join-group { display: flex; flex-direction: column; gap: 10px; }
.join-group input {
  width: 100%; padding: 15px 16px; border: 2px solid rgba(148,163,184,0.2); border-radius: var(--radius-sm);
  font-size: 22px; text-align: center; letter-spacing: 12px; font-weight: 700; outline: none;
  transition: all 0.25s ease; color: var(--text); background: rgba(255,255,255,0.5);
  backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px);
}
.join-group input:focus { border-color: var(--primary); background: rgba(255,255,255,0.8); box-shadow: 0 0 0 4px rgba(99,102,241,0.1); }
.join-group input::placeholder { letter-spacing: 1px; font-size: 14px; font-weight: 400; color: #94a3b8; }
.join-group .btn { width: 100%; }
.error-msg { color: var(--danger); font-size: 13px; margin-top: 12px; min-height: 20px; font-weight: 500; }
.btn-back-lobby {
  display: inline-block; margin-top: 18px; color: var(--text-light); font-size: 14px; font-weight: 500;
  text-decoration: none; letter-spacing: 1px; transition: color 0.2s;
}
.btn-back-lobby:hover { color: var(--primary); }

.waiting-card h2 { font-size: 21px; font-weight: 700; margin-bottom: 28px; }
.waiting-icon { position: relative; width: 70px; height: 70px; margin: 0 auto 28px; }
.pulse-dot { position: absolute; inset: 23px; border-radius: 50%; background: var(--primary-gradient); box-shadow: 0 0 16px var(--primary-glow); }
.pulse-ring { position: absolute; inset: 0; border-radius: 50%; border: 3px solid var(--primary); animation: pulse-ring 1.8s ease-out infinite; }
@keyframes pulse-ring { 0% { transform: scale(0.5); opacity: 1; } 100% { transform: scale(1.4); opacity: 0; } }
.room-code-display { background: linear-gradient(135deg,rgba(248,250,252,0.8),rgba(241,245,249,0.8)); border: 1px solid rgba(148,163,184,0.15); border-radius: var(--radius-sm); padding: 22px; margin-bottom: 18px; }
.room-code-label { display: block; font-size: 11px; color: var(--text-light); margin-bottom: 10px; text-transform: uppercase; letter-spacing: 3px; font-weight: 600; }
.room-code-value { font-size: 46px; font-weight: 800; letter-spacing: 16px; background: var(--primary-gradient); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.hint { color: var(--text-muted); font-size: 13px; margin-bottom: 22px; line-height: 1.6; }
.btn-cancel { margin-top: 8px; color: var(--text-light); border-color: transparent; }
.btn-cancel:hover { color: var(--danger); background: rgba(254,226,226,0.5); }

#screen-game { flex-direction: column; padding: 12px 12px 16px; gap: 6px; overflow: hidden; }
.game-header { display: flex; align-items: center; justify-content: space-between; width: 100%; max-width: 440px; gap: 8px; }
.player-card {
  display: flex; align-items: center; gap: 10px; padding: 8px 14px; border-radius: var(--radius-sm);
  background: var(--card); backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px);
  border: 1.5px solid transparent; box-shadow: 0 2px 12px rgba(0,0,0,0.05); transition: all 0.35s ease;
}
.player-card.active-turn { border-color: var(--primary); box-shadow: 0 4px 20px rgba(99,102,241,0.2); background: rgba(255,255,255,0.9); }
.player-token {
  width: 34px; height: 34px; border-radius: 50%; flex-shrink: 0;
  display: flex; align-items: center; justify-content: center;
  font-size: 17px; font-weight: 700; font-family: "KaiTi","STKaiti","楷体","SimSun","Noto Serif SC",serif;
  box-shadow: 1px 2px 6px rgba(0,0,0,0.15);
}
.red-token {
  background: radial-gradient(circle at 35% 35%, #fff5ee, #f0c8a8 65%, #d4956b);
  border: 2px solid #8b2500; color: #8b1a1a;
}
.dark-token {
  background: radial-gradient(circle at 35% 35%, #f0f0f0, #b0b8c4 65%, #6b7a8d);
  border: 2px solid #3a4a5c; color: #1a2a3a;
}
.player-info { display: flex; flex-direction: column; min-width: 0; }
.player-name { font-size: 14px; font-weight: 700; white-space: nowrap; }
.player-tag { font-size: 11px; color: var(--primary); font-weight: 600; }

.timer-display {
  display: flex; align-items: baseline; gap: 3px; padding: 10px 20px;
  border-radius: var(--radius-sm); background: var(--card); backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px); box-shadow: 0 2px 12px rgba(0,0,0,0.05);
  flex-shrink: 0; transition: all 0.3s ease;
}
.timer-value { font-size: 32px; font-weight: 800; font-variant-numeric: tabular-nums; color: var(--text); transition: color 0.3s; }
.timer-display.warning .timer-value { color: var(--warning); }
.timer-display.danger .timer-value { color: var(--danger); }
.timer-display.danger { animation: timer-pulse 0.5s ease-in-out infinite alternate; box-shadow: 0 2px 20px rgba(239,68,68,0.15); }
@keyframes timer-pulse { from { transform: scale(1); } to { transform: scale(1.06); } }
.timer-label { font-size: 12px; color: var(--text-light); font-weight: 600; }

.game-status { font-size: 15px; font-weight: 700; color: var(--text-muted); text-align: center; padding: 2px 0; transition: color 0.3s; letter-spacing: 1px; }
.board-wrapper { display: flex; align-items: center; justify-content: center; flex: 1; width: 100%; min-height: 0; overflow: hidden; }
#game-board { border-radius: 10px; box-shadow: 0 8px 32px rgba(0,0,0,0.12), 0 2px 8px rgba(0,0,0,0.06); touch-action: none; cursor: pointer; }
.game-footer { display: flex; gap: 14px; justify-content: center; padding-top: 4px; flex-shrink: 0; }

.modal-overlay {
  position: fixed; inset: 0; background: rgba(15,23,42,0.35); backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px);
  display: flex; align-items: center; justify-content: center; padding: 24px; z-index: 1000;
  opacity: 0; pointer-events: none; transition: opacity 0.3s ease;
}
.modal-overlay.active { opacity: 1; pointer-events: auto; }
.modal-card {
  background: rgba(255,255,255,0.88); backdrop-filter: blur(24px); -webkit-backdrop-filter: blur(24px);
  border: 1px solid var(--card-border); border-radius: var(--radius); box-shadow: var(--shadow-lg);
  padding: 40px 34px; max-width: 350px; width: 100%; text-align: center;
  transform: scale(0.88) translateY(20px); transition: transform 0.35s cubic-bezier(0.34,1.56,0.64,1);
}
.modal-overlay.active .modal-card { transform: scale(1) translateY(0); }
.modal-card h3 { font-size: 24px; font-weight: 800; margin-bottom: 10px; }
.modal-card p { color: var(--text-muted); font-size: 14px; margin-bottom: 30px; line-height: 1.6; }
.modal-actions { display: flex; gap: 12px; }
.modal-actions .btn { flex: 1; }

@media (max-height: 640px) {
  #screen-game { padding: 6px 8px 8px; gap: 3px; }
  .player-card { padding: 6px 10px; }
  .timer-value { font-size: 26px; }
  .game-status { font-size: 13px; }
  .card { padding: 32px 26px; }
}
@media (min-width: 768px) {
  .card { padding: 52px 44px; max-width: 420px; }
  .game-header { max-width: 520px; }
}