* { margin: 0; padding: 0; box-sizing: border-box; }
:root {
  --primary: #6366f1; --primary-gradient: linear-gradient(135deg, #6366f1, #8b5cf6);
  --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-border: rgba(255,255,255,0.55);
  --text: #1e293b; --text-muted: #64748b; --text-light: #94a3b8;
  --border: rgba(148,163,184,0.25); --danger: #ef4444;
  --shadow: 0 8px 32px rgba(0,0,0,0.06); --radius: 22px; --radius-sm: 14px;
}
html, body {
  height: 100%; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, 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: #a5b4fc; 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, transform 0.4s; 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: 14px; background: linear-gradient(135deg, #1e293b, #6366f1); -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-grid { display: inline-grid; grid-template-columns: repeat(3, 28px); gap: 4px; }
.lg-x { color: #ef4444; font-size: 22px; font-weight: 800; text-align: center; }
.lg-o { color: #3b82f6; font-size: 22px; font-weight: 800; text-align: center; }
.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; outline: none; }
.btn:active { transform: scale(0.96); }
.btn-primary { background: var(--primary-gradient); color: #fff; width: 100%; box-shadow: 0 4px 18px var(--primary-glow); letter-spacing: 2px; }
.btn-accent { background: var(--primary-gradient); color: #fff; 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%; }
.btn-outline { background: rgba(255,255,255,0.5); color: var(--text); border: 1.5px solid var(--border); padding: 10px 24px; font-size: 14px; }
.btn-danger-outline { color: var(--danger); border-color: rgba(239,68,68,0.25); }
.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: #fff; border: none; transition: all 0.25s; }
.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-medium { background: linear-gradient(135deg, #fbbf24, #f59e0b); box-shadow: 0 4px 14px rgba(245,158,11,0.3); }
#btn-ai-hard { background: linear-gradient(135deg, #f87171, #ef4444); box-shadow: 0 4px 14px rgba(239,68,68,0.3); }
.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; color: var(--text); background: rgba(255,255,255,0.5); }
.join-group input:focus { border-color: var(--primary); background: rgba(255,255,255,0.8); }
.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-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; }
.btn-cancel { margin-top: 8px; color: var(--text-light); border-color: transparent; }

/* ===== 游戏界面 ===== */
#screen-game { flex-direction: column; padding: 16px; gap: 10px; overflow: hidden; }
.game-header { display: flex; align-items: center; justify-content: center; gap: 16px; }
.player-card { display: flex; align-items: center; gap: 8px; padding: 8px 14px; background: var(--card); backdrop-filter: blur(16px); border-radius: var(--radius-sm); border: 1.5px solid transparent; box-shadow: 0 2px 12px rgba(0,0,0,0.05); transition: all 0.35s; }
.player-card.active-turn { border-color: var(--primary); background: rgba(255,255,255,0.9); box-shadow: 0 4px 20px rgba(99,102,241,0.2); }
.player-token { width: 28px; height: 28px; border-radius: 50%; display: flex; align-items: center; justify-content: center; font-size: 16px; font-weight: 900; flex-shrink: 0; }
.x-token { background: linear-gradient(135deg, #fecaca, #fca5a5); color: #dc2626; border: 1.5px solid #f87171; }
.o-token { background: linear-gradient(135deg, #bfdbfe, #93c5fd); color: #2563eb; border: 1.5px solid #60a5fa; }
.player-info { display: flex; flex-direction: column; }
.player-name { font-size: 13px; font-weight: 700; }
.player-tag { font-size: 10px; color: var(--primary); font-weight: 600; }
.vs-badge { font-size: 12px; font-weight: 800; color: var(--text-light); letter-spacing: 2px; }
.game-status { font-size: 14px; font-weight: 700; color: var(--text-muted); text-align: center; letter-spacing: 1px; }
.board-wrapper { display: flex; align-items: center; justify-content: center; flex: 1; min-height: 0; }
.ttt-board { display: grid; grid-template-columns: repeat(3, 1fr); width: min(85vw, 340px); aspect-ratio: 1; }

/* 格子用边框画经典 # */
.cell { display: flex; align-items: center; justify-content: center; cursor: pointer; position: relative; transition: background 0.15s; border-right: 3px solid rgba(148,163,184,0.3); border-bottom: 3px solid rgba(148,163,184,0.3); }
.cell:nth-child(3n) { border-right: none; }
.cell:nth-child(n+7) { border-bottom: none; }
.cell:hover:not(.placed):not(.disabled) { background: rgba(99,102,241,0.06); }
.cell.disabled { cursor: default; pointer-events: none; }

/* CSS 绘制的 X 和 O */
.mark { position: absolute; inset: 16%; display: flex; align-items: center; justify-content: center; animation: mark-pop 0.3s cubic-bezier(0.34,1.56,0.64,1); }
@keyframes mark-pop { 0%{transform:scale(0);opacity:0} 100%{transform:scale(1);opacity:1} }
.mark.x::before, .mark.x::after { content: ''; position: absolute; width: clamp(5px,1.8vw,8px); height: 100%; border-radius: 4px; background: #ef4444; }
.mark.x::before { transform: rotate(45deg); }
.mark.x::after { transform: rotate(-45deg); }
.mark.x { filter: drop-shadow(0 2px 6px rgba(239,68,68,0.25)); }
.mark.o::before { content: ''; position: absolute; inset: 8%; border: clamp(4px,1.5vw,7px) solid #3b82f6; border-radius: 50%; }
.mark.o { filter: drop-shadow(0 2px 6px rgba(59,130,246,0.25)); }

/* 胜利 */
.cell.win-cell { background: rgba(250,204,21,0.12); }
.cell.win-cell .mark { animation: win-glow 0.7s ease-in-out infinite alternate; }
@keyframes win-glow { 0%{filter:drop-shadow(0 0 4px rgba(250,204,21,0.3)) brightness(1)} 100%{filter:drop-shadow(0 0 14px rgba(250,204,21,0.5)) brightness(1.1)} }

.game-footer { display: flex; gap: 10px; justify-content: center; flex-shrink: 0; }

/* 弹窗 */
.modal-overlay { position: fixed; inset: 0; background: rgba(15,23,42,0.35); 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; }
.modal-overlay.active { opacity: 1; pointer-events: auto; }
.modal-card { background: rgba(255,255,255,0.88); backdrop-filter: blur(24px); border: 1px solid var(--card-border); border-radius: var(--radius); box-shadow: 0 20px 60px rgba(0,0,0,0.1); 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; white-space: pre-line; }
.modal-actions { display: flex; gap: 12px; }
.modal-actions .btn { flex: 1; }