:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
    --success-color: #27ae60;
    --board-bg: #dcb35c;
    --board-border: #8b4513;
    --bg-color: #f5f7fa;
    --text-color: #2c3e50;
    --shadow-color: rgba(0,0,0,0.1);
    --glass-bg: rgba(255,255,255,0.9);
    --glass-border: rgba(255,255,255,0.3);
    --cell-size: 40px;
}

html[data-theme="dark"], [data-theme="dark"] {
    --bg-color: #1a1a2e;
    --text-color: #eaeaea;
    --glass-bg: rgba(26,26,46,0.9);
    --glass-border: rgba(255,255,255,0.1);
    --shadow-color: rgba(0,0,0,0.3);
}

* { margin:0; padding:0; box-sizing:border-box; }

body {
    font-family: 'Noto Sans TC', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: var(--text-color);
}

.container { max-width:1400px; margin:0 auto; padding:20px; }

/* ── Header ── */
.game-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 20px;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border-radius: 15px;
    margin-bottom: 20px;
    box-shadow: 0 8px 32px var(--shadow-color);
    border: 1px solid var(--glass-border);
    flex-wrap: wrap;
    gap: 10px;
}

.logo { display:flex; align-items:center; gap:12px; }
.logo-icon { font-size:2rem; animation:pulse 2s infinite; }
.logo h1 {
    font-size: 2rem; font-weight: 700;
    background: linear-gradient(135deg,#2c3e50,#3498db);
    -webkit-background-clip: text; background-clip: text;
    -webkit-text-fill-color: transparent; color: transparent;
}

/* 線上狀態列 */
.online-status {
    display: flex; align-items: center; gap: 10px;
    background: rgba(39,174,96,0.15);
    border: 1px solid rgba(39,174,96,0.4);
    border-radius: 20px; padding: 6px 14px;
    font-size: 0.9rem; font-weight: 600;
}
.online-dot {
    width: 8px; height: 8px; border-radius: 50%;
    background: #27ae60; animation: pulse 1.5s infinite;
}
.room-code-badge {
    background: rgba(0,0,0,0.1);
    border-radius: 6px; padding: 2px 8px;
    font-family: monospace; font-size: 0.95rem; letter-spacing: 2px;
}
.btn-sm-danger {
    background: rgba(231,76,60,0.15); border: 1px solid rgba(231,76,60,0.4);
    color: #e74c3c; border-radius: 8px; padding: 4px 10px;
    font-size: 0.8rem; cursor: pointer; font-weight: 600;
    transition: all 0.2s;
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
}
.btn-sm-danger:hover { background: rgba(231,76,60,0.3); }

.icon-btn {
    background: transparent; border: none; cursor: pointer;
    font-size: 1.5rem; padding: 8px; border-radius: 50%;
    transition: all 0.3s;
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
}
.icon-btn:hover { background: rgba(0,0,0,0.1); transform: rotate(15deg); }

/* ── Game Area ── */
.game-area {
    display: grid;
    grid-template-columns: 280px 1fr 280px;
    gap: 20px;
    align-items: start;
}

/* ── Info Panel ── */
.info-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border-radius: 15px; padding: 20px;
    box-shadow: 0 8px 32px var(--shadow-color);
    border: 1px solid var(--glass-border);
    height: fit-content;
}

.player-card {
    display: flex; align-items: center; gap: 15px;
    padding: 15px; background: rgba(255,255,255,0.5);
    border-radius: 12px; margin-bottom: 15px;
    transition: all 0.3s; border: 2px solid transparent;
}
.player-card.active {
    border-color: var(--secondary-color);
    background: rgba(52,152,219,0.1);
    transform: scale(1.02);
}
.player-card.my-turn { border-color: #27ae60; background: rgba(39,174,96,0.1); }

.player-avatar {
    width: 50px; height: 50px; border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-size: 1.5rem; background: white;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}
.player-info h3 { font-size:1.1rem; margin-bottom:4px; }
.player-status { font-size:0.85rem; color:var(--secondary-color); font-weight:500; }

.vs-badge { text-align:center; font-size:1.5rem; font-weight:700; color:var(--accent-color); margin:10px 0; }

.stats-panel {
    display: grid; grid-template-columns: 1fr 1fr 1fr;
    gap: 10px; margin: 20px 0; padding: 15px;
    background: rgba(0,0,0,0.05); border-radius: 12px;
}
.stat-item { text-align:center; }
.stat-label { display:block; font-size:0.75rem; color:var(--text-color); opacity:0.7; margin-bottom:4px; }
.stat-value { font-size:1.2rem; font-weight:700; color:var(--secondary-color); }

/* Steps counter uses primary color */
.stat-item:first-child .stat-value { color: var(--primary-color); }

.ai-controls { margin-top:20px; padding-top:20px; border-top:1px solid rgba(0,0,0,0.1); }
.ai-label { display:block; font-size:0.9rem; font-weight:600; margin-bottom:8px; }

/* ── Difficulty segmented control ── */
.diff-segmented {
    display: flex;
    background: rgba(0,0,0,0.06);
    border-radius: 8px;
    padding: 3px;
    gap: 3px;
}
html[data-theme="dark"] .diff-segmented { background: rgba(255,255,255,0.08); }
.diff-seg-btn {
    flex: 1; padding: 8px 4px;
    border: none; border-radius: 6px;
    font-size: 0.85rem; font-weight: 500;
    cursor: pointer;
    background: transparent;
    color: var(--text-color);
    transition: all 0.2s;
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
    font-family: 'Noto Sans TC', sans-serif;
}
.diff-seg-btn.is-active {
    background: white;
    box-shadow: 0 1px 4px rgba(0,0,0,0.15);
    color: var(--primary-color);
    font-weight: 700;
}
html[data-theme="dark"] .diff-seg-btn.is-active {
    background: rgba(255,255,255,0.15);
    box-shadow: none;
}
#ai-difficulty:focus { outline:none; border-color:var(--secondary-color); }

/* ── Turn Banner (mobile only) ── */
.turn-banner {
    display: none;
}

/* ── Board ── */
.board-container {
    position: relative; padding: 20px;
    background: var(--glass-bg); backdrop-filter: blur(10px);
    border-radius: 15px;
    box-shadow: 0 8px 32px var(--shadow-color);
    border: 1px solid var(--glass-border);
    display: flex; justify-content: center; align-items: center;
}

.board {
    position: relative;
    width: 600px; height: 600px;
    background: linear-gradient(135deg, #dcb35c 0%, #b8860b 100%);
    border: 8px solid var(--board-border);
    border-radius: 8px;
    box-shadow: inset 0 0 20px rgba(0,0,0,0.2), 0 10px 30px rgba(0,0,0,0.3);
    cursor: crosshair; overflow: hidden;
    touch-action: none;
    -webkit-tap-highlight-color: transparent;
    user-select: none;
}

.board::before {
    content: '';
    position: absolute;
    top: 20px; left: 20px; right: 20px; bottom: 20px;
    background-image:
        linear-gradient(rgba(139,69,19,0.3) 1px, transparent 1px),
        linear-gradient(90deg, rgba(139,69,19,0.3) 1px, transparent 1px);
    background-size: var(--cell-size, 40px) var(--cell-size, 40px);
    pointer-events: none;
}

.star-point {
    position: absolute; width: 8px; height: 8px;
    background: rgba(139,69,19,0.6); border-radius: 50%;
    transform: translate(-50%,-50%); pointer-events: none;
}

/* ── Pieces ── */
.piece {
    position: absolute;
    width: calc(var(--cell-size, 40px) * 0.82);
    height: calc(var(--cell-size, 40px) * 0.82);
    border-radius: 50%; transform: translate(-50%,-50%);
    cursor: pointer; animation: dropIn 0.3s ease-out; z-index: 10;
    transition: transform 0.15s;
}
.piece.black {
    background: radial-gradient(circle at 30% 30%, #666, #1a1a1a);
    box-shadow: 2px 2px 6px rgba(0,0,0,0.4), inset -2px -2px 6px rgba(255,255,255,0.1);
}
.piece.white {
    background: radial-gradient(circle at 30% 30%, #fff, #e0e0e0);
    box-shadow: 2px 2px 6px rgba(0,0,0,0.3), inset -2px -2px 6px rgba(0,0,0,0.1);
}
.piece:hover { transform: translate(-50%,-50%) scale(1.1); z-index: 20; }

.piece.last-move::after {
    content: ''; position: absolute; top:50%; left:50%;
    transform: translate(-50%,-50%); width:10px; height:10px;
    background: rgba(231,76,60,0.8); border-radius:50%; animation: pulse 1.2s infinite;
}
.piece.winning {
    animation: winPulse 0.6s ease-out forwards;
    box-shadow: 0 0 0 3px rgba(231,76,60,0.9), 0 0 16px rgba(231,76,60,0.6);
    z-index: 30;
}

.win-line {
    position: absolute; background: rgba(231,76,60,0.8);
    border-radius: 4px; transform: translate(-50%,-50%);
    z-index: 5; animation: highlight 0.5s ease-out;
}

/* ── Buttons ── */
.controls-panel { display:flex; flex-direction:column; gap:15px; }
.control-group { display:flex; flex-direction:column; gap:10px; }

.btn {
    display: flex; align-items: center; justify-content: center; gap: 8px;
    padding: 12px 20px; border: none; border-radius: 10px;
    font-size: 1rem; font-weight: 600; cursor: pointer;
    transition: all 0.3s; font-family: 'Noto Sans TC', sans-serif;
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
    user-select: none;
}
.btn-primary  { background: linear-gradient(135deg,#2c3e50,#34495e); color:white; box-shadow:0 4px 6px rgba(0,0,0,0.2); }
.btn-secondary{ background: linear-gradient(135deg,#95a5a6,#7f8c8d); color:white; box-shadow:0 4px 6px rgba(0,0,0,0.2); }
.btn-accent   { background: linear-gradient(135deg,#e74c3c,#c0392b); color:white; box-shadow:0 4px 6px rgba(0,0,0,0.2); }
.btn-online   { background: linear-gradient(135deg,#27ae60,#1e8449); color:white; box-shadow:0 4px 6px rgba(0,0,0,0.2); }
.btn-outline  { background: transparent; border: 2px solid var(--secondary-color); color: var(--secondary-color); }

.btn-primary:hover,.btn-secondary:hover,.btn-accent:hover,.btn-online:hover {
    transform: translateY(-2px); box-shadow: 0 6px 12px rgba(0,0,0,0.3);
}
.btn-outline:hover { background: var(--secondary-color); color: white; transform: translateY(-2px); }
.btn:disabled { opacity:0.5; cursor:not-allowed; transform:none !important; }
.btn-full { width:100%; }

/* ── AI Status ── */
.ai-status {
    position: fixed; top:50%; left:50%; transform: translate(-50%,-50%);
    background: rgba(0,0,0,0.88); color: white;
    padding: 20px 40px; border-radius: 15px; z-index: 1001; text-align:center;
    backdrop-filter: blur(6px);
    border: 1px solid rgba(255,255,255,0.1);
}
.ai-thinking { display:flex; align-items:center; gap:15px; font-size:1.2rem; }
.spinner {
    width:24px; height:24px; border:3px solid rgba(255,255,255,0.3);
    border-top-color:white; border-radius:50%; animation: spin 1s linear infinite;
}
.hidden { display:none !important; }

/* ── Modals ── */
.modal {
    position: fixed; top:0; left:0; width:100%; height:100%;
    background: rgba(0,0,0,0.7); display: none;
    align-items: center; justify-content: center;
    z-index: 1000; backdrop-filter: blur(5px);
}
.modal-content {
    background: white; border-radius: 20px; padding: 30px;
    max-width: 420px; width: 90%; text-align: center;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3); animation: slideUp 0.3s ease-out;
}
.winner-icon { font-size:4rem; margin-bottom:10px; animation: bounce 1s ease-out; }
.modal-content h2 { font-size:1.8rem; color:var(--primary-color); margin-bottom:10px; }
.winner-stats {
    display:grid; grid-template-columns:1fr 1fr; gap:15px;
    margin:20px 0; padding:15px; background:rgba(0,0,0,0.05); border-radius:12px;
}
.winner-stats .stat { text-align:center; }
.modal-footer { display:flex; gap:10px; margin-top:20px; }

/* ── Lobby ── */
.lobby-content { max-width: 400px; }
.lobby-title { font-size:1.6rem; margin-bottom:20px; }

.lobby-divider {
    text-align:center; margin:20px 0; position:relative;
    color: #999; font-size:0.9rem;
}
.lobby-divider::before {
    content:''; position:absolute; top:50%; left:0; right:0; height:1px;
    background:rgba(0,0,0,0.15); z-index:0;
}
.lobby-divider span { background:white; padding:0 12px; position:relative; z-index:1; }

.join-room-group { display:flex; gap:8px; }
.room-input {
    flex:1; padding:12px; border-radius:10px;
    border: 2px solid rgba(0,0,0,0.15); font-size:1.1rem;
    text-align:center; letter-spacing:3px; font-weight:700;
    text-transform: uppercase; font-family: monospace;
    transition: border 0.2s;
}
.room-input:focus { outline:none; border-color:var(--secondary-color); }

.room-created-box {
    background: linear-gradient(135deg, rgba(39,174,96,0.1), rgba(46,204,113,0.1));
    border: 2px solid rgba(39,174,96,0.3);
    border-radius: 15px; padding: 20px; margin-bottom: 20px;
}
.room-label { font-size:0.9rem; color:#666; margin-bottom:8px; }
.room-code-display {
    font-size: 2.8rem; font-weight: 900; letter-spacing: 8px;
    font-family: monospace; color: #27ae60;
    margin: 10px 0 15px;
}
.copy-hint { font-size:0.8rem; color:#888; margin-top:10px; }

.waiting-animation {
    display:flex; align-items:center; justify-content:center;
    gap:12px; font-size:1rem; color:#555;
}

.joined-box { padding:20px 0; }
.joined-box p { font-size:1.1rem; margin:8px 0; }

.lobby-error {
    color: #e74c3c; font-size:0.9rem;
    margin-top:10px; padding:8px; border-radius:8px;
    background: rgba(231,76,60,0.1);
}

/* ── Animations ── */
@keyframes dropIn {
    0%   { transform:translate(-50%,-50%) scale(0); opacity:0; }
    50%  { transform:translate(-50%,-50%) scale(1.2); }
    100% { transform:translate(-50%,-50%) scale(1); opacity:1; }
}
@keyframes winPulse {
    0%   { transform:translate(-50%,-50%) scale(1); }
    40%  { transform:translate(-50%,-50%) scale(1.25); }
    100% { transform:translate(-50%,-50%) scale(1.1); }
}
@keyframes pulse { 0%,100%{opacity:1} 50%{opacity:0.5} }
@keyframes spin { to{transform:rotate(360deg)} }
@keyframes slideUp { from{transform:translateY(50px);opacity:0} to{transform:translateY(0);opacity:1} }
@keyframes bounce {
    0%,20%,50%,80%,100%{transform:translateY(0)}
    40%{transform:translateY(-20px)} 60%{transform:translateY(-10px)}
}
@keyframes highlight {
    0%{opacity:0;transform:translate(-50%,-50%) scale(0.5)}
    100%{opacity:1;transform:translate(-50%,-50%) scale(1)}
}

/* ── Responsive ── */
@media (max-width:1200px) {
    .game-area { grid-template-columns: 240px 1fr 240px; }
    .board { width:500px; height:500px; }
}
@media (max-width:900px) {
    /* ── Layout ── */
    .game-area {
        grid-template-columns: 1fr;
        /* 88px = button bar; env() handles iPhone home indicator */
        padding-bottom: calc(88px + env(safe-area-inset-bottom, 0px));
    }
    .info-panel,.controls-panel { order: 2; }
    .board-container { order: 1; padding: 10px; flex-direction: column; align-items: center; }
    /* Also constrain by viewport height so header never scrolls off.
       360px ≈ header + banner + info-panel + bar. On phones ≥700px tall
       the 92vw value still wins so board size is unchanged. */
    .board {
        width:  min(92vw, calc(100dvh - 360px), 500px);
        height: min(92vw, calc(100dvh - 360px), 500px);
    }

    /* ── Turn Banner ── */
    .turn-banner {
        display: flex;
        align-items: center;
        justify-content: center;
        gap: 8px;
        width: 100%;
        padding: 8px 16px;
        margin-bottom: 10px;
        border-radius: 10px;
        font-size: 1rem;
        font-weight: 700;
        letter-spacing: 0.5px;
        background: rgba(255,255,255,0.75);
        backdrop-filter: blur(8px);
        border: 1px solid rgba(255,255,255,0.5);
        color: var(--primary-color);
        transition: all 0.3s;
    }
    .turn-banner.is-my-turn {
        background: rgba(39,174,96,0.2);
        border-color: rgba(39,174,96,0.4);
        color: #1a7a42;
    }
    .turn-banner.is-ai-turn {
        background: rgba(231,76,60,0.1);
        border-color: rgba(231,76,60,0.2);
        color: #a93226;
    }
    .turn-banner-dot {
        width: 10px; height: 10px;
        border-radius: 50%;
        background: var(--secondary-color);
        animation: pulse 1.2s infinite;
        flex-shrink: 0;
    }

    /* ── Info Panel ── */
    .info-panel {
        display: flex;
        flex-direction: row;
        flex-wrap: wrap;
        align-items: center;
        gap: 8px;
        padding: 12px;
    }
    .player-card {
        flex: 1; min-width: 130px;
        margin-bottom: 0; padding: 10px;
    }
    .vs-badge { margin: 0; }
    .stats-panel { width: 100%; margin: 8px 0 0; padding: 10px; }
    .ai-controls { width: 100%; margin-top: 8px; padding-top: 8px; }

    /* ── Controls Panel → Fixed Bottom Bar ── */
    .controls-panel {
        position: fixed;
        bottom: 0; left: 0; right: 0;
        z-index: 500;
        display: flex;
        flex-direction: row;
        gap: 0;
        padding: 8px 8px;
        padding-bottom: calc(8px + env(safe-area-inset-bottom, 0px));
        background: var(--glass-bg);
        backdrop-filter: blur(20px);
        -webkit-backdrop-filter: blur(20px);
        border-top: 1px solid var(--glass-border);
        box-shadow: 0 -4px 24px var(--shadow-color);
        border-radius: 0;
    }
    /* 底部工具列：把 control-group 展平，讓四顆按鈕平分空間 */
    .control-group {
        display: contents;
    }
    /* ⚠️ 以下樣式只限底部工具列的按鈕（.controls-panel .btn）
       不可套用在 modal 等其他地方的 .btn，否則純文字按鈕的文字會消失 */
    .controls-panel .btn {
        flex: 1;
        flex-direction: column;
        gap: 2px;
        padding: 6px 4px;
        border-radius: 10px;
        font-size: 0;        /* 隱藏預設大小，由 .btn-icon/.btn-text 覆蓋 */
        min-height: 56px;
    }
    /* 用 px 而非 rem，避免部分 Android WebKit 在父 font-size:0 時 rem 解析為 0 */
    .controls-panel .btn .btn-icon {
        font-size: 22px;
        line-height: 1;
        color: inherit;
        display: block;
    }
    .controls-panel .btn .btn-text {
        font-size: 11px;
        font-weight: 600;
        line-height: 1.2;
        color: inherit;
        display: block;
        white-space: nowrap;
    }

    /* Keep hover/active effects but no translateY on mobile */
    .btn-primary:hover,.btn-secondary:hover,.btn-accent:hover,.btn-online:hover {
        transform: none;
        filter: brightness(1.08);
    }
    .btn-outline:hover { transform: none; }
}
@media (max-width:600px) {
    .container { padding: 10px; }
    .modal-footer { flex-direction: column; }
    .join-room-group { flex-direction: column; }
    .logo h1 { font-size: 1.5rem; }
    .player-avatar { width: 40px; height: 40px; font-size: 1.2rem; }
    .player-info h3 { font-size: 0.95rem; }
}