* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        }
        
        body {
            background: linear-gradient(135deg, #1a1a2e, #16213e);
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
            color: #e6e6e6;
        }
        
        .game-container {
            width: 100%;
            max-width: 1000px;
            background: rgba(255, 255, 255, 0.05);
            backdrop-filter: blur(10px);
            border-radius: 20px;
            box-shadow: 0 15px 35px rgba(0, 0, 0, 0.5);
            overflow: hidden;
            padding: 30px;
            display: flex;
            flex-direction: column;
            gap: 25px;
        }
        
        .game-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding-bottom: 15px;
            border-bottom: 1px solid rgba(255, 255, 255, 0.1);
        }
        
        .game-title {
            font-size: 2.5rem;
            font-weight: 800;
            background: linear-gradient(45deg, #00b4db, #0083b0);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
            text-transform: uppercase;
            letter-spacing: 1px;
        }
        
        .header-controls {
            display: flex;
            gap: 15px;
            align-items: center;
        }
        
        .header-btn {
            padding: 10px 15px;
            border: none;
            border-radius: 8px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            display: flex;
            justify-content: center;
            align-items: center;
            gap: 8px;
        }
        
        .btn-primary {
            background: linear-gradient(135deg, #00b4db, #0083b0);
            color: white;
            box-shadow: 0 4px 10px rgba(0, 180, 219, 0.4);
        }
        
        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 15px rgba(0, 180, 219, 0.6);
        }
        
        .btn-secondary {
            background: rgba(255, 255, 255, 0.05);
            color: #e6e6e6;
        }
        
        .btn-secondary:hover {
            background: rgba(255, 255, 255, 0.1);
        }
        
        select {
            padding: 10px 15px;
            border-radius: 8px;
            background: rgba(0, 0, 0, 0.2);
            color: white;
            border: 1px solid rgba(255, 255, 255, 0.1);
            cursor: pointer;
        }
        
        .score-board {
            display: flex;
            gap: 20px;
            background: rgba(0, 0, 0, 0.2);
            padding: 10px 20px;
            border-radius: 50px;
        }
        
        .score {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 5px;
        }
        
        .score-value {
            font-size: 1.8rem;
            font-weight: 700;
        }
        
        .score-label {
            font-size: 0.9rem;
            opacity: 0.8;
        }
        
        .main-content {
            display: flex;
            gap: 30px;
            min-height: 400px;
        }
        
        .board-container {
            flex: 1;
            display: flex;
            justify-content: center;
            align-items: center;
        }
        
        .game-board {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            grid-template-rows: repeat(3, 1fr);
            gap: 12px;
            width: 100%;
            max-width: 400px;
            aspect-ratio: 1;
            background: linear-gradient(135deg, #0f3460, #1a1a2e);
            padding: 15px;
            border-radius: 15px;
            box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
        }
        
        .cell {
            background: rgba(255, 255, 255, 0.05);
            border-radius: 10px;
            display: flex;
            justify-content: center;
            align-items: center;
            font-size: 4rem;
            cursor: pointer;
            transition: all 0.3s ease;
            position: relative;
            overflow: hidden;
        }
        
        .cell:hover {
            background: rgba(255, 255, 255, 0.1);
            transform: translateY(-3px);
        }
        
        .cell.x::before, .cell.x::after {
            content: '';
            position: absolute;
            width: 70%;
            height: 8%;
            background: #00b4db;
            border-radius: 10px;
        }
        
        .cell.x::before {
            transform: rotate(45deg);
        }
        
        .cell.x::after {
            transform: rotate(-45deg);
        }
        
        .cell.o::before {
            content: '';
            position: absolute;
            width: 60%;
            height: 60%;
            border: 8px solid #0083b0;
            border-radius: 50%;
        }
        
        .cell.win {
            animation: winPulse 1.5s infinite;
        }
        
        @keyframes winPulse {
            0% { box-shadow: 0 0 0 0 rgba(0, 180, 219, 0.4); }
            70% { box-shadow: 0 0 0 15px rgba(0, 180, 219, 0); }
            100% { box-shadow: 0 0 0 0 rgba(0, 180, 219, 0); }
        }
        
        .game-controls {
            width: 300px;
            display: flex;
            flex-direction: column;
            gap: 20px;
        }
        
        .game-status {
            background: rgba(0, 0, 0, 0.2);
            padding: 20px;
            border-radius: 15px;
        }
        
        .status-text {
            font-size: 1.2rem;
            text-align: center;
            margin-bottom: 15px;
            min-height: 60px;
            display: flex;
            align-items: center;
            justify-content: center;
        }
        
        .player-turn {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 10px;
            margin-top: 15px;
        }
        
        .turn-indicator {
            width: 20px;
            height: 20px;
            border-radius: 50%;
        }
        
        .turn-x {
            background: #00b4db;
        }
        
        .turn-o {
            background: #0083b0;
        }
        
        .mode-selection {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            gap: 30px;
            width: 100%;
            min-height: 400px;
        }
        
        .mode-title {
            font-size: 2.5rem;
            font-weight: 700;
            background: linear-gradient(45deg, #00b4db, #0083b0);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
            margin-bottom: 20px;
        }
        
        .mode-options {
            display: flex;
            gap: 30px;
            flex-wrap: wrap;
            justify-content: center;
        }
        
        .mode-option {
            width: 200px;
            height: 200px;
            background: rgba(255, 255, 255, 0.05);
            border-radius: 15px;
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            gap: 15px;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .mode-option:hover {
            background: rgba(255, 255, 255, 0.1);
            transform: translateY(-5px);
            box-shadow: 0 10px 20px rgba(0, 0, 0, 0.3);
        }
        
        .mode-icon {
            font-size: 4rem;
            color: #00b4db;
        }
        
        .mode-name {
            font-size: 1.5rem;
            font-weight: 600;
        }
        
        .custom-settings {
            display: flex;
            flex-direction: column;
            gap: 20px;
            align-items: center;
            width: 100%;
        }
        
        .setting-group {
            display: flex;
            flex-direction: column;
            gap: 10px;
            width: 100%;
            max-width: 500px;
        }
        
        .setting-label {
            font-size: 1.1rem;
            font-weight: 600;
            color: #00b4db;
            text-align: center;
        }
        
        .size-options {
            display: flex;
            flex-wrap: wrap;
            gap: 10px;
            justify-content: center;
        }
        
        .size-option {
            padding: 12px 20px;
            background: rgba(255, 255, 255, 0.05);
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .size-option:hover {
            background: rgba(255, 255, 255, 0.1);
        }
        
        .size-option.selected {
            background: linear-gradient(135deg, #00b4db, #0083b0);
            color: white;
            box-shadow: 0 4px 10px rgba(0, 180, 219, 0.4);
        }
        
        .win-options {
            display: flex;
            flex-wrap: wrap;
            gap: 10px;
            justify-content: center;
        }
        
        .win-option {
            padding: 12px 20px;
            background: rgba(255, 255, 255, 0.05);
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .win-option:hover {
            background: rgba(255, 255, 255, 0.1);
        }
        
        .win-option.selected {
            background: linear-gradient(135deg, #00b4db, #0083b0);
            color: white;
            box-shadow: 0 4px 10px rgba(0, 180, 219, 0.4);
        }
        
        .start-btn {
            padding: 15px 30px;
            background: linear-gradient(135deg, #00b4db, #0083b0);
            color: white;
            border: none;
            border-radius: 50px;
            font-size: 1.2rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            box-shadow: 0 5px 15px rgba(0, 180, 219, 0.4);
            margin-top: 20px;
        }
        
        .start-btn:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 20px rgba(0, 180, 219, 0.6);
        }
        
        .hidden {
            display: none;
        }
        
        @media (max-width: 900px) {
            .game-container {
                max-width: 95%;
                padding: 20px;
            }
            
            .main-content {
                flex-direction: column;
            }
            
            .game-controls {
                width: 100%;
            }
            
            .game-board {
                max-width: 300px;
            }
            
            .cell {
                font-size: 3rem;
            }
            
            .mode-options {
                flex-direction: column;
                align-items: center;
            }
            
            .game-header {
                flex-direction: column;
                gap: 15px;
            }
            
            .header-controls {
                flex-wrap: wrap;
                justify-content: center;
            }
            
            .mode-option {
                width: 250px;
            }
        }
        
        @media (max-width: 480px) {
            .game-title {
                font-size: 2rem;
            }
            
            .score-board {
                flex-direction: column;
                gap: 10px;
                border-radius: 15px;
            }
            
            .mode-option {
                width: 200px;
                height: 150px;
            }
            
            .mode-icon {
                font-size: 3rem;
            }
        }
        
        /* Animations */
        @keyframes fadeIn {
            from { opacity: 0; transform: scale(0.9); }
            to { opacity: 1; transform: scale(1); }
        }
        
        .fade-in {
            animation: fadeIn 0.5s ease-out;
        }
        
        @keyframes confetti {
            0% { transform: translateY(0) rotate(0); opacity: 1; }
            100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
        }
        
        .confetti {
            position: fixed;
            width: 10px;
            height: 10px;
            background: #00b4db;
            opacity: 0;
            z-index: 1000;
        }