body {
            box-sizing: border-box;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            margin: 0;
            padding: 20px;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
        }

        /* Intro Animation */
        .intro-overlay {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100vh;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            display: flex;
            align-items: center;
            justify-content: center;
            z-index: 9999;
            animation: slideUp 2s ease-in-out 2s forwards;
        }

        .intro-content {
            text-align: center;
            color: white;
        }

        .intro-text {
            font-size: 4rem;
            font-weight: bold;
            opacity: 0;
            animation: fadeInUp 1s ease-out 0.5s forwards;
            margin-bottom: 20px;
        }

        .intro-subtitle {
            font-size: 1.5rem;
            opacity: 0;
            animation: fadeInUp 1s ease-out 1s forwards;
        }

        @keyframes fadeInUp {
            from { opacity: 0; transform: translateY(30px); }
            to { opacity: 1; transform: translateY(0); }
        }

        @keyframes slideUp {
            to { transform: translateY(-100%); }
        }

        .main-content {
            opacity: 0;
            animation: fadeIn 1s ease-out 2.5s forwards;
        }

        @keyframes fadeIn {
            to { opacity: 1; }
        }

        .container {
            max-width: 500px;
            width: 100%;
            text-align: center;
        }

        .game-title {
            color: white;
            font-size: 3rem;
            font-weight: bold;
            margin-bottom: 10px;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .game-subtitle {
            color: rgba(255,255,255,0.9);
            font-size: 1.2rem;
            margin-bottom: 30px;
        }

        .game-container {
            background: white;
            border-radius: 25px;
            padding: 40px;
            box-shadow: 0 15px 35px rgba(0,0,0,0.2);
            margin-bottom: 30px;
        }

        /* Game Mode Selection Styles */
        .game-mode-selection {
            margin-bottom: 25px;
            padding: 20px;
            background: #f8f9fa;
            border-radius: 15px;
        }

        .mode-btn, .difficulty-btn {
            background: #e9ecef;
            border: 2px solid #dee2e6;
            border-radius: 20px;
            padding: 10px 15px;
            font-size: 0.9rem;
            font-weight: bold;
            cursor: pointer;
            transition: all 0.3s ease;
            display: inline-flex;
            align-items: center;
            gap: 8px;
            color: #495057;
        }

        .mode-btn:hover, .difficulty-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
        }

        .mode-btn.active, .difficulty-btn.active {
            background: linear-gradient(45deg, #667eea, #764ba2);
            color: white;
            border-color: #667eea;
        }

        .ai-difficulty {
            margin-top: 15px;
            padding-top: 15px;
            border-top: 2px solid #dee2e6;
        }

        .game-status {
            font-size: 1.5rem;
            font-weight: bold;
            margin-bottom: 25px;
            color: #333;
            min-height: 50px;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .game-board {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 15px;
            max-width: 300px;
            margin: 0 auto 25px;
        }

        .game-cell {
            aspect-ratio: 1;
            background: #f8f9fa;
            border: 3px solid #e9ecef;
            border-radius: 15px;
            font-size: 2.5rem;
            font-weight: bold;
            cursor: pointer;
            transition: all 0.3s ease;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .game-cell:hover {
            background: #e9ecef;
            transform: scale(1.05);
            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
        }

        .game-cell.x {
            color: #ff6b6b;
            background: #ffe0e0;
            border-color: #ff6b6b;
        }

        .game-cell.o {
            color: #4ecdc4;
            background: #e0f7f7;
            border-color: #4ecdc4;
        }

        .game-cell.winning {
            background: #fff3cd !important;
            border-color: #ffc107 !important;
            animation: pulse 0.5s ease-in-out;
        }

        .game-cell.ai-thinking {
            background: #fff3cd;
            border-color: #ffc107;
            animation: thinking 1s ease-in-out infinite;
        }

        @keyframes pulse {
            0%, 100% { transform: scale(1); }
            50% { transform: scale(1.1); }
        }

        @keyframes thinking {
            0%, 100% { opacity: 1; }
            50% { opacity: 0.7; }
        }

        .game-timer {
            font-size: 1.2rem;
            font-weight: bold;
            color: #333;
            margin-bottom: 15px;
            padding: 10px 20px;
            background: #f8f9fa;
            border-radius: 20px;
            display: inline-block;
        }

        .game-controls {
            display: flex;
            gap: 10px;
            justify-content: center;
            flex-wrap: wrap;
            margin-bottom: 20px;
        }

        .control-btn {
            background: linear-gradient(45deg, #667eea, #764ba2);
            color: white;
            border: none;
            padding: 12px 20px;
            border-radius: 25px;
            font-size: 1rem;
            font-weight: bold;
            cursor: pointer;
            transition: all 0.3s ease;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .control-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 8px 20px rgba(0,0,0,0.2);
        }

        .control-btn.reset-scores {
            background: linear-gradient(45deg, #ff6b6b, #ee5a52);
        }

        .control-btn:disabled {
            opacity: 0.6;
            cursor: not-allowed;
            transform: none;
        }

        .score-board {
            display: flex;
            justify-content: space-around;
            margin-bottom: 20px;
            background: #f8f9fa;
            border-radius: 15px;
            padding: 15px;
        }

        .score-item {
            text-align: center;
        }

        .score-label {
            font-size: 0.9rem;
            color: #666;
            margin-bottom: 5px;
        }

        .score-value {
            font-size: 1.5rem;
            font-weight: bold;
        }

        .score-x {
            color: #ff6b6b;
        }

        .score-o {
            color: #4ecdc4;
        }

        .developer-button {
            background: rgba(255,255,255,0.1);
            backdrop-filter: blur(10px);
            border: 2px solid rgba(255,255,255,0.2);
            border-radius: 20px;
            padding: 20px;
            color: white;
            cursor: pointer;
            transition: all 0.3s ease;
            text-align: center;
            width: 100%;
            max-width: 300px;
            margin: 0 auto;
        }

        .developer-button:hover {
            background: rgba(255,255,255,0.2);
            border-color: rgba(255,255,255,0.4);
            transform: translateY(-3px);
            box-shadow: 0 10px 25px rgba(0,0,0,0.2);
        }

        .developer-title {
            font-size: 1.2rem;
            font-weight: bold;
            margin-bottom: 8px;
        }

        .developer-name {
            font-size: 1rem;
            color: rgba(255,255,255,0.9);
        }

        .social-modal {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0,0,0,0.8);
            display: none;
            align-items: center;
            justify-content: center;
            z-index: 10000;
            padding: 20px;
        }

        .social-modal.show {
            display: flex;
        }

        .social-content {
            background: white;
            border-radius: 25px;
            padding: 40px;
            max-width: 500px;
            width: 100%;
            text-align: center;
            position: relative;
            animation: modalSlideIn 0.3s ease-out;
        }

        @keyframes modalSlideIn {
            from { transform: scale(0.8); opacity: 0; }
            to { transform: scale(1); opacity: 1; }
        }

        .close-modal {
            position: absolute;
            top: 15px;
            right: 20px;
            background: none;
            border: none;
            font-size: 1.5rem;
            cursor: pointer;
            color: #666;
            transition: color 0.3s ease;
        }

        .close-modal:hover {
            color: #333;
        }

        .modal-title {
            font-size: 1.8rem;
            font-weight: bold;
            margin-bottom: 10px;
            color: #333;
        }

        .modal-subtitle {
            font-size: 1.1rem;
            color: #666;
            margin-bottom: 30px;
        }

        .social-links {
            display: flex;
            justify-content: center;
            gap: 15px;
            flex-wrap: wrap;
        }

        .social-btn {
            display: inline-flex;
            align-items: center;
            gap: 8px;
            padding: 12px 20px;
            border-radius: 25px;
            text-decoration: none;
            color: white;
            font-weight: bold;
            transition: all 0.3s ease;
            font-size: 0.9rem;
        }

        .social-btn:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 20px rgba(0,0,0,0.3);
            color: white;
        }

        .social-btn.facebook {
            background: linear-gradient(45deg, #3b5998, #8b9dc3);
        }

        .social-btn.twitter {
            background: linear-gradient(45deg, #1da1f2, #0d8bd9);
        }

        .social-btn.instagram {
            background: linear-gradient(45deg, #e1306c, #fd1d1d);
        }

        .social-btn.linkedin {
            background: linear-gradient(45deg, #0077b5, #00a0dc);
        }

        .social-btn.github {
            background: linear-gradient(45deg, #333, #666);
        }

        .social-btn.youtube {
            background: linear-gradient(45deg, #ff0000, #cc0000);
        }

        /* Mobile Responsive */
        @media (max-width: 768px) {
            body {
                padding: 10px;
            }
            
            .intro-text {
                font-size: 2.5rem;
            }
            
            .game-title {
                font-size: 2.5rem;
            }
            
            .game-container {
                padding: 25px;
            }
            
            .game-cell {
                font-size: 2rem;
            }
            
            .game-board {
                max-width: 280px;
                gap: 10px;
            }
            
            .game-controls {
                gap: 8px;
            }
            
            .control-btn {
                padding: 10px 15px;
                font-size: 0.9rem;
            }
            
            .mode-btn, .difficulty-btn {
                padding: 8px 12px;
                font-size: 0.8rem;
            }
            
            .social-links {
                gap: 10px;
            }
            
            .social-btn {
                padding: 10px 15px;
                font-size: 0.8rem;
            }
            
            .social-content {
                padding: 30px 20px;
            }
        }

        @media (max-width: 480px) {
            .intro-text {
                font-size: 2rem;
            }
            
            .game-title {
                font-size: 2rem;
            }
            
            .game-board {
                max-width: 250px;
            }
            
            .game-cell {
                font-size: 1.8rem;
            }
            
            .control-btn {
                padding: 8px 12px;
                font-size: 0.8rem;
            }
            
            .mode-btn, .difficulty-btn {
                padding: 6px 10px;
                font-size: 0.75rem;
            }
            
            .social-btn {
                padding: 8px 12px;
                font-size: 0.75rem;
            }
        }