* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    user-select: none;
}

body {
    background: #f5f7fb;
    font-family: 'Roboto', system-ui, -apple-system, 'Segoe UI', sans-serif;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    margin: 0;
}

.game-container {
    max-width: 600px;
    width: 100%;
    background: #ffffff;
    border-radius: 36px;
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.1), 0 4px 8px rgba(0, 0, 0, 0.02);
    transition: all 0.2s ease;
    padding: 28px 24px 36px;
}

.game-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    margin-bottom: 20px;
    gap: 12px;
}

h1 {
    font-size: 1.9rem;
    font-weight: 700;
    background: linear-gradient(135deg, #202124, #3c4043);
    background-clip: text;
    -webkit-background-clip: text;
    color: transparent;
    letter-spacing: -0.3px;
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

h1::before {
    content: "🎮";
    background: none;
    -webkit-background-clip: unset;
    color: #5f6368;
}

/* 模式切换滑动胶囊 */
.mode-slider-container {
    background: #e8eaed;
    border-radius: 48px;
    padding: 4px;
    width: 280px;
    position: relative;
    display: flex;
    cursor: default;
    box-shadow: inset 0 1px 2px rgba(0,0,0,0.05), 0 1px 2px rgba(0,0,0,0.02);
}
.mode-slider-options {
    display: flex;
    width: 100%;
    position: relative;
    z-index: 2;
}
.mode-option {
    flex: 1;
    text-align: center;
    padding: 6px 0;
    font-weight: 500;
    font-size: 0.85rem;
    border-radius: 40px;
    transition: color 0.2s ease;
    z-index: 3;
    cursor: pointer;
    color: #5f6368;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
}
.mode-slider-container.active-twoPlayer .mode-option[data-mode="twoPlayer"],
.mode-slider-container.active-vsAI .mode-option[data-mode="vsAI"],
.mode-slider-container.active-online .mode-option[data-mode="online"] {
    color: #ffffff;
    text-shadow: 0 1px 2px rgba(0,0,0,0.1);
    font-weight: 600;
}
.mode-slider-bg {
    position: absolute;
    top: 4px;
    left: 4px;
    width: calc(33.33% - 4px);
    height: calc(100% - 8px);
    background: #1a73e8;
    border-radius: 40px;
    transition: transform 0.25s cubic-bezier(0.2, 0.9, 0.4, 1.1);
    z-index: 1;
    box-shadow: 0 1px 4px rgba(0,0,0,0.2);
}
.mode-slider-container.active-vsAI .mode-slider-bg {
    transform: translateX(100%);
}
.mode-slider-container.active-online .mode-slider-bg {
    transform: translateX(200%);
}
.mode-slider-container.active-twoPlayer .mode-slider-bg {
    transform: translateX(0%);
}

.action-group {
    display: flex;
    gap: 12px;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 8px;
}

.reset-btn, .ai-first-btn {
    background: rgba(26, 115, 232, 0.08);
    border: none;
    font-family: 'Roboto', sans-serif;
    font-weight: 500;
    font-size: 0.85rem;
    padding: 8px 18px;
    border-radius: 40px;
    color: #1a73e8;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 6px;
    transition: all 0.2s ease;
    backdrop-filter: blur(4px);
}

.reset-btn:hover, .ai-first-btn:hover {
    background: rgba(26, 115, 232, 0.16);
    transform: scale(0.97);
}

.status-area {
    background: #f8f9fa;
    border-radius: 60px;
    padding: 12px 20px;
    margin: 16px 0 28px 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
    box-shadow: inset 0 1px 2px rgba(0,0,0,0.02), 0 2px 4px rgba(0,0,0,0.02);
}

.turn-indicator {
    display: flex;
    align-items: center;
    gap: 14px;
    font-weight: 500;
}

.turn-label {
    color: #5f6368;
    font-size: 0.95rem;
}

/* 玩家滑动胶囊 */
.players-slider-container {
    background: #e8eaed;
    border-radius: 48px;
    padding: 4px;
    width: 140px;
    position: relative;
    display: flex;
    cursor: default;
    box-shadow: inset 0 1px 2px rgba(0,0,0,0.05), 0 1px 2px rgba(0,0,0,0.02);
}

.slider-options {
    display: flex;
    width: 100%;
    position: relative;
    z-index: 2;
}

.player-option {
    flex: 1;
    text-align: center;
    padding: 6px 0;
    font-weight: 700;
    font-size: 1.1rem;
    border-radius: 40px;
    transition: color 0.2s ease;
    z-index: 3;
    cursor: default;
    letter-spacing: 0.5px;
}

.player-option.x-opt {
    color: #b85c4a;
}
.player-option.o-opt {
    color: #4c8fbf;
}

.players-slider-container.active-x .player-option.x-opt,
.players-slider-container.active-o .player-option.o-opt {
    color: white;
    text-shadow: 0 1px 2px rgba(0,0,0,0.1);
}

.slider-bg {
    position: absolute;
    top: 4px;
    left: 4px;
    width: calc(50% - 4px);
    height: calc(100% - 8px);
    background: #e34234;
    border-radius: 40px;
    transition: transform 0.25s cubic-bezier(0.2, 0.9, 0.4, 1.1), background 0.2s;
    z-index: 1;
    box-shadow: 0 1px 4px rgba(0,0,0,0.2);
}

.players-slider-container.active-o .slider-bg {
    transform: translateX(100%);
    background: #1e88e5;
}

.players-slider-container.active-x .slider-bg {
    transform: translateX(0%);
    background: #e34234;
}

.status-message {
    font-size: 0.85rem;
    font-weight: 500;
    background: #e8eaed;
    padding: 6px 16px;
    border-radius: 32px;
    color: #3c4043;
}

.board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 14px;
    margin-bottom: 28px;
}

.cell {
    aspect-ratio: 1 / 1;
    background: #ffffff;
    border-radius: 28px;
    box-shadow: 0 8px 18px rgba(0, 0, 0, 0.05), 0 1px 2px rgba(0, 0, 0, 0.03);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: clamp(2.8rem, 12vw, 5rem);
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.2, 0.9, 0.4, 1.1);
    border: 1px solid rgba(0, 0, 0, 0.02);
}

.cell:hover {
    transform: translateY(-3px);
    box-shadow: 0 16px 24px rgba(0, 0, 0, 0.08), 0 4px 8px rgba(0, 0, 0, 0.02);
    background: #fefefe;
}

.cell:active {
    transform: scale(0.97);
}

.cell[data-value="X"] {
    color: #e34234;
    text-shadow: 0 2px 6px rgba(227, 66, 52, 0.2);
}

.cell[data-value="O"] {
    color: #1e88e5;
    text-shadow: 0 2px 6px rgba(30, 136, 229, 0.2);
}

.cell.winner-highlight {
    background: linear-gradient(145deg, #e9f5e9, #d4ecd4);
    box-shadow: 0 0 0 2px #34a853, 0 12px 24px rgba(52, 168, 83, 0.2);
    transform: scale(1.01);
    color: #1e7e34;
}

.board.inactive .cell {
    cursor: default;
}

.footer-note {
    text-align: center;
    font-size: 0.75rem;
    color: #9aa0a6;
    margin-top: 20px;
    font-weight: 400;
    letter-spacing: 0.3px;
}

@media (max-width: 520px) {
    .game-container {
        padding: 20px 18px 28px;
    }
    .board {
        gap: 10px;
    }
    .cell {
        border-radius: 20px;
    }
    .players-slider-container {
        width: 120px;
    }
    .mode-slider-container {
        width: 240px;
    }
    .status-message {
        font-size: 0.7rem;
    }
}

@keyframes gentlePop {
    0% { transform: scale(0.98); opacity: 0.9; }
    100% { transform: scale(1); opacity: 1; }
}
.board-refresh {
    animation: gentlePop 0.2s ease-out;
}

/* 联机面板样式 */
#onlinePanel {
    margin-top: 16px;
    padding: 12px;
    background: #f1f3f4;
    border-radius: 24px;
}
#onlinePanel input {
    flex: 1;
    padding: 8px 12px;
    border-radius: 40px;
    border: 1px solid #dadce0;
    font-family: inherit;
    font-size: 0.9rem;
}
#onlinePanel button {
    background: rgba(26, 115, 232, 0.08);
    border: none;
    font-family: 'Roboto', sans-serif;
    font-weight: 500;
    font-size: 0.85rem;
    padding: 8px 18px;
    border-radius: 40px;
    color: #1a73e8;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    transition: all 0.2s ease;
}
#onlinePanel button:hover {
    background: rgba(26, 115, 232, 0.16);
    transform: scale(0.97);
}
#onlineRoomDisplay {
    font-size: 0.9rem;
    color: #1a73e8;
    margin-top: 8px;
}
#onlineStatus {
    font-size: 0.8rem;
    color: #5f6368;
    margin-top: 4px;
    }