:root {
            --primary: #8a2be2;
            --secondary: #4a00e0;
            --background: #0f172a;
            --glass-bg: rgba(255, 255, 255, 0.05);
            --glass-border: rgba(255, 255, 255, 0.1);
            --text: #f8fafc;
            --x-color: #00ffcc;
            --o-color: #ff3366;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Outfit', sans-serif;
        }

        body {
            background: linear-gradient(135deg, var(--background) 0%, #1e1b4b 100%);
            min-height: 100vh;
            width: 100vw;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            padding: 80px 0 20px;
            color: var(--text);
            overflow-x: hidden;
            overflow-y: auto;
        }

        /* Ambient background glow */
        body::before {
            content: '';
            position: absolute;
            width: 500px;
            height: 500px;
            background: radial-gradient(circle, rgba(138,43,226,0.2) 0%, rgba(0,0,0,0) 70%);
            top: -100px;
            left: -100px;
            border-radius: 50%;
            z-index: -1;
            animation: pulseGlow 10s infinite alternate;
        }

        @keyframes pulseGlow {
            0% { transform: scale(1); opacity: 0.5; }
            100% { transform: scale(1.5); opacity: 0.8; }
        }

        .home-btn {
            position: absolute;
            top: 20px;
            left: 20px;
            color: var(--text);
            text-decoration: none;
            font-size: clamp(0.9rem, 3vmin, 1.1rem);
            font-weight: 500;
            padding: 8px 16px;
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid var(--glass-border);
            border-radius: 8px;
            transition: all 0.3s;
            z-index: 100;
            backdrop-filter: blur(5px);
        }

        .home-btn:hover {
            background: rgba(255, 255, 255, 0.2);
            transform: translateX(-5px);
            box-shadow: 0 5px 15px rgba(0,0,0,0.3);
            border-color: rgba(255, 255, 255, 0.3);
        }

        @media (max-width: 600px) {
            .home-btn { /* Adjust position on small screens if necessary */
                top: 10px;
                left: 10px;
                padding: 6px 12px;
            }
        }

        .header {
            text-align: center;
            margin-bottom: min(2vh, 1rem); /* Dynamic margin */
            animation: fadeInDown 1s ease-out;
            width: 90%;
            max-width: 400px;
        }

        .title {
            font-size: clamp(2rem, 6vmin, 3.5rem); /* Dynamic font size */
            font-weight: 700;
            background: linear-gradient(45deg, #00ffcc, #8a2be2);
            -webkit-background-clip: text;
            background-clip: text;
            -webkit-text-fill-color: transparent;
            text-shadow: 0 0 30px rgba(138, 43, 226, 0.3);
            margin-bottom: 0.2rem;
        }

        .status {
            font-size: clamp(1rem, 4vmin, 1.5rem);
            font-weight: 500;
            height: clamp(1.5rem, 5vmin, 2rem);
            transition: color 0.3s;
        }

        .status.x-turn { color: var(--x-color); }
        .status.o-turn { color: var(--o-color); }

        .scoreboard {
            display: flex;
            justify-content: space-between;
            align-items: center;
            width: 90%;
            max-width: 400px;
            margin: 0 auto min(2vh, 1rem) auto;
            background: rgba(255, 255, 255, 0.05);
            padding: min(2vmin, 1rem);
            border-radius: 15px;
            border: 1px solid var(--glass-border);
            animation: fadeIn 1s ease-out;
        }

        .player-card {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 0.2rem;
            width: 40%;
        }

        .player-name-input {
            background: rgba(0, 0, 0, 0.3);
            border: 1px solid var(--glass-border);
            color: white;
            font-family: 'Outfit', sans-serif;
            font-size: clamp(0.9rem, 3vmin, 1.1rem);
            font-weight: 700;
            padding: 0.3rem;
            border-radius: 8px;
            text-align: center;
            width: 100%;
            outline: none;
            transition: all 0.3s;
        }

        .player-name-input:focus {
            background: rgba(0, 0, 0, 0.5);
            border-color: rgba(255, 255, 255, 0.3);
        }

        .player-name-input.x-name {
            color: var(--x-color);
            border-color: rgba(0, 255, 204, 0.3);
        }

        .player-name-input.o-name {
            color: var(--o-color);
            border-color: rgba(255, 51, 102, 0.3);
        }

        .player-name-input:disabled {
            opacity: 0.8;
            cursor: not-allowed;
            background: rgba(0, 0, 0, 0.5);
        }

        .score {
            font-size: clamp(1.5rem, 5vmin, 2rem);
            font-weight: 700;
        }

        .score.x-score { color: var(--x-color); }
        .score.o-score { color: var(--o-color); }

        .score-divider {
            font-size: clamp(1rem, 4vmin, 1.5rem);
            font-weight: 700;
            color: rgba(255, 255, 255, 0.5);
        }

        .game-container {
            position: relative;
            padding: min(3vmin, 1.2rem);
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 20px;
            backdrop-filter: blur(10px);
            box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5), inset 0 0 20px rgba(255,255,255,0.02);
            animation: fadeIn 1s ease-out;
            width: 90%;
            max-width: 380px;
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        .board {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            grid-template-rows: repeat(3, 1fr);
            gap: min(2vmin, 10px);
            margin-bottom: min(2vmin, 1rem);
            width: 100%;
            max-width: min(280px, 40vh); /* Shrinks board heavily if screen is short */
            aspect-ratio: 1 / 1; /* Keep it perfectly square */
        }

        .cell {
            background: rgba(0, 0, 0, 0.3);
            border: 1px solid rgba(255, 255, 255, 0.05);
            border-radius: 10px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: clamp(2.5rem, 8vmin, 4rem);
            font-weight: 700;
            cursor: pointer;
            transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
            box-shadow: inset 0 2px 5px rgba(0,0,0,0.5);
        }

        .cell:hover:not(.occupied) {
            transform: translateY(-5px);
            background: rgba(255, 255, 255, 0.1);
            box-shadow: 0 10px 20px rgba(0,0,0,0.3), inset 0 2px 5px rgba(255,255,255,0.1);
        }

        .cell.x {
            color: var(--x-color);
            text-shadow: 0 0 20px rgba(0, 255, 204, 0.5);
            animation: popIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
        }

        .cell.o {
            color: var(--o-color);
            text-shadow: 0 0 20px rgba(255, 51, 102, 0.5);
            animation: popIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
        }

        .cell.winning-cell {
            background: rgba(255, 255, 255, 0.2);
            box-shadow: 0 0 30px rgba(255,255,255,0.2);
            transform: scale(1.05);
            z-index: 10;
        }

        .controls {
            display: flex;
            gap: min(2vmin, 1rem);
            width: 100%;
            margin-top: 0;
        }

        .btn {
            flex: 1;
            padding: clamp(0.5rem, 2vmin, 1rem);
            font-size: clamp(0.8rem, 3vmin, 1.1rem);
            font-weight: 700;
            color: white;
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid var(--glass-border);
            border-radius: 10px;
            cursor: pointer;
            transition: all 0.3s;
            text-transform: uppercase;
            letter-spacing: 1px;
        }

        .btn:hover {
            background: rgba(255, 255, 255, 0.2);
            transform: translateY(-2px);
        }

        .btn.primary {
            background: linear-gradient(45deg, var(--primary), var(--secondary));
            border: none;
            box-shadow: 0 4px 15px rgba(138, 43, 226, 0.4);
        }

        .btn.primary:hover {
            background: linear-gradient(45deg, #9b4dff, #5c1aff);
            box-shadow: 0 8px 25px rgba(138, 43, 226, 0.6);
        }

        .btn.active-mode {
            background: rgba(0, 255, 204, 0.2);
            border-color: var(--x-color);
            color: var(--x-color);
            box-shadow: inset 0 0 10px rgba(0, 255, 204, 0.2);
        }

        .difficulty-container {
            width: 100%;
            margin-top: min(2vmin, 1rem);
            display: flex;
            align-items: center;
            gap: 0.5rem;
            background: rgba(255, 255, 255, 0.05);
            padding: clamp(0.4rem, 2vmin, 0.8rem) clamp(0.5rem, 2vmin, 1rem);
            border-radius: 10px;
            border: 1px solid var(--glass-border);
            transition: all 0.3s;
        }

        .difficulty-container.hidden {
            display: none;
            opacity: 0;
            transform: translateY(-10px);
            margin-top: 0;
        }

        .difficulty-label {
            font-size: clamp(0.8rem, 3vmin, 1.1rem);
            font-weight: 500;
            color: var(--text);
            white-space: nowrap;
        }

        .difficulty-select {
            flex: 1;
            padding: clamp(0.2rem, 1vmin, 0.5rem);
            font-size: clamp(0.8rem, 3vmin, 1.1rem);
            font-weight: 500;
            color: white;
            background: rgba(0, 0, 0, 0.5);
            border: 1px solid var(--glass-border);
            border-radius: 5px;
            cursor: pointer;
            outline: none;
            font-family: 'Outfit', sans-serif;
        }
        
        .difficulty-select option {
            background-color: var(--background);
            color: white;
        }

        /* Footer styles */
        .site-footer {
            width: 100%;
            text-align: center;
            padding: 1.5rem 1rem;
            margin-top: 1.5rem;
            border-top: 1px solid rgba(255, 255, 255, 0.1);
            color: rgba(255, 255, 255, 0.6);
            font-size: 0.85rem;
        }
        .site-footer a {
            color: #00ffcc;
            text-decoration: none;
        }
        .site-footer a:hover {
            text-decoration: underline;
        }

        @media (max-width: 600px) {
            body {
                padding: 70px 10px 20px;
                justify-content: flex-start;
            }
            .home-btn {
                top: 10px;
                left: 10px;
                padding: 6px 12px;
            }
        }