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

        body {
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            background: linear-gradient(45deg, #1a1a1a, #2c3e50);
            background-size: 400% 400%;
            animation: gradientBG 15s ease infinite;
        }

        @keyframes gradientBG {
            0% { background-position: 0% 50%; }
            50% { background-position: 100% 50%; }
            100% { background-position: 0% 50%; }
        }

        .calculator {
            background: rgba(255, 255, 255, 0.1);
            backdrop-filter: blur(10px);
            border-radius: 20px;
            padding: 25px;
            box-shadow: 0 0 30px rgba(0, 255, 255, 0.2);
            border: 1px solid rgba(255, 255, 255, 0.1);
            position: relative;
            overflow: hidden;
        }

        .calculator::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(
                90deg,
                transparent,
                rgba(255, 255, 255, 0.2),
                transparent
            );
            transition: 0.5s;
        }

        .calculator:hover::before {
            left: 100%;
        }

        #display {
            width: 100%;
            height: 80px;
            background: rgba(0, 0, 0, 0.3);
            border: none;
            border-radius: 10px;
            color: #00ff9d;
            font-size: 2.5em;
            text-align: right;
            padding: 15px;
            margin-bottom: 20px;
            font-family: 'Digital-7', monospace;
            text-shadow: 0 0 10px rgba(0, 255, 157, 0.5);
        }

        .buttons {
            display: grid;
            grid-template-columns: repeat(5, 1fr);
            gap: 10px;
        }

        .btn {
            padding: 20px;
            border: none;
            border-radius: 12px;
            font-size: 1.2em;
            cursor: pointer;
            transition: all 0.3s ease;
            background: rgba(255, 255, 255, 0.05);
            color: white;
            position: relative;
            overflow: hidden;
        }

        .btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(
                90deg,
                transparent,
                rgba(255, 255, 255, 0.2),
                transparent
            );
            transition: 0.5s;
        }

        .btn:hover::before {
            left: 100%;
        }

        .number {
            background: linear-gradient(45deg, #3498db, #2980b9);
        }

        .operator {
            background: linear-gradient(45deg, #e74c3c, #c0392b);
        }

        .scientific {
            background: linear-gradient(45deg, #9b59b6, #8e44ad);
        }

        .equal {
            background: linear-gradient(45deg, #2ecc71, #27ae60);
            grid-row: span 2;
        }

        .clear {
            background: linear-gradient(45deg, #f1c40f, #f39c12);
        }

        .btn:active {
            transform: scale(0.95);
            filter: brightness(1.2);
        }

        .special {
            background: linear-gradient(45deg, #1abc9c, #16a085);
        }