* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Orbitron', sans-serif;
            background: linear-gradient(135deg, #0c0c0c 0%, #1a1a2e 35%, #16213e 100%);
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
            overflow: hidden;
            position: relative;
        }

        body::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: 
                radial-gradient(circle at 20% 30%, rgba(0, 255, 255, 0.1) 0%, transparent 50%),
                radial-gradient(circle at 80% 70%, rgba(138, 43, 226, 0.1) 0%, transparent 50%),
                radial-gradient(circle at 40% 80%, rgba(0, 123, 255, 0.1) 0%, transparent 50%);
            pointer-events: none;
        }

        main {
            z-index: 1;
        }

        #box {
            background: rgba(255, 255, 255, 0.05);
            -webkit-backdrop-filter: blur(20px);
            backdrop-filter: blur(20px);
            border: 1px solid rgba(255, 255, 255, 0.1);
            border-radius: 25px;
            padding: 30px;
            box-shadow: 
                0 25px 50px rgba(0, 0, 0, 0.5),
                inset 0 1px 0 rgba(255, 255, 255, 0.1);
            max-width: 420px;
            width: 100%;
            position: relative;
        }

        #box::before {
            content: '';
            position: absolute;
            top: -2px;
            left: -2px;
            right: -2px;
            bottom: -2px;
            background: linear-gradient(45deg, #00ffff, #8a2be2, #007bff, #00ffff);
            border-radius: 27px;
            z-index: -1;
            opacity: 0.3;
            animation: borderGlow 3s ease-in-out infinite alternate;
        }

        @keyframes borderGlow {
            0% { opacity: 0.3; }
            100% { opacity: 0.6; }
        }

        .screen {
            margin-bottom: 25px;
        }

        #textarea {
            width: 100%;
            height: 80px;
            background: rgba(0, 0, 0, 0.6);
            border: 2px solid rgba(0, 255, 255, 0.3);
            border-radius: 15px;
            padding: 20px;
            font-family: 'Orbitron', monospace;
            font-size: 24px;
            font-weight: 700;
            color: #00ffff;
            text-align: right;
            box-shadow: 
                inset 0 4px 10px rgba(0, 0, 0, 0.5),
                0 0 20px rgba(0, 255, 255, 0.2);
            transition: all 0.3s ease;
            outline: none;
        }

        #textarea:focus {
            border-color: rgba(0, 255, 255, 0.8);
            box-shadow: 
                inset 0 4px 10px rgba(0, 0, 0, 0.5),
                0 0 30px rgba(0, 255, 255, 0.4);
        }

        #textarea::placeholder {
            color: rgba(0, 255, 255, 0.4);
            font-size: 16px;
        }

        .btn {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 15px;
        }

        button {
            height: 65px;
            font-family: 'Orbitron', sans-serif;
            font-size: 18px;
            font-weight: 700;
            border: none;
            border-radius: 15px;
            cursor: pointer;
            transition: all 0.2s ease;
            position: relative;
            overflow: hidden;
            background: rgba(255, 255, 255, 0.1);
            -webkit-backdrop-filter: blur(10px);
            backdrop-filter: blur(10px);
            border: 1px solid rgba(255, 255, 255, 0.2);
            color: #ffffff;
            text-shadow: 0 0 10px rgba(255, 255, 255, 0.5);
        }

        button::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: left 0.5s;
        }

        button:hover::before {
            left: 100%;
        }

        button:hover {
            transform: translateY(-2px);
            background: rgba(255, 255, 255, 0.15);
            box-shadow: 
                0 10px 25px rgba(0, 0, 0, 0.3),
                0 0 20px rgba(0, 255, 255, 0.3);
            border-color: rgba(0, 255, 255, 0.5);
        }

        button:active {
            transform: translateY(1px) scale(0.98);
            box-shadow: 
                0 2px 10px rgba(0, 0, 0, 0.4),
                inset 0 2px 5px rgba(0, 0, 0, 0.3);
        }

        /* Number buttons */
        #zero, #one, #two, #three, #four, #five, #six, #seven, #eight, #nine {
            color: #ffffff;
        }

        #zero, #one, #two, #three, #four, #five, #six, #seven, #eight, #nine:hover {
            box-shadow: 
                0 10px 25px rgba(0, 0, 0, 0.3),
                0 0 20px rgba(0, 123, 255, 0.4);
            border-color: rgba(0, 123, 255, 0.6);
        }

        /* Operator buttons */
        #divide, #multiply, #minus, #plus {
            background: rgba(138, 43, 226, 0.2);
            color: #da70d6;
            border-color: rgba(138, 43, 226, 0.4);
        }

        #divide:hover, #multiply:hover, #minus:hover, #plus:hover {
            background: rgba(138, 43, 226, 0.3);
            box-shadow: 
                0 10px 25px rgba(0, 0, 0, 0.3),
                0 0 20px rgba(138, 43, 226, 0.5);
            border-color: rgba(138, 43, 226, 0.8);
        }

        /* Special buttons */
        #allClr, #clear, #delete {
            background: rgba(255, 69, 58, 0.2);
            color: #ff6b6b;
            border-color: rgba(255, 69, 58, 0.4);
        }

        #allClr:hover, #clear:hover, #delete:hover {
            background: rgba(255, 69, 58, 0.3);
            box-shadow: 
                0 10px 25px rgba(0, 0, 0, 0.3),
                0 0 20px rgba(255, 69, 58, 0.5);
            border-color: rgba(255, 69, 58, 0.8);
        }

        /* Equal button */
        #equal {
            grid-row: span 2;
            background: rgba(0, 255, 255, 0.2);
            color: #00ffff;
            border-color: rgba(0, 255, 255, 0.4);
            font-size: 22px;
            font-weight: 900;
        }

        #equal:hover {
            background: rgba(0, 255, 255, 0.3);
            box-shadow: 
                0 15px 30px rgba(0, 0, 0, 0.4),
                0 0 30px rgba(0, 255, 255, 0.6);
            border-color: rgba(0, 255, 255, 0.8);
        }

        /* Zero button spans two columns */
        #zero {
            grid-column: span 2;
        }

        /* Point button */
        #point {
            color: #ffffff;
            font-size: 24px;
        }

        /* Mobile responsiveness */
        @media (max-width: 480px) {
            body {
                padding: 10px;
            }

            #box {
                padding: 20px;
                border-radius: 20px;
            }

            #textarea {
                height: 70px;
                font-size: 20px;
                padding: 15px;
            }

            button {
                height: 55px;
                font-size: 16px;
            }

            .btn {
                gap: 12px;
            }

            #equal {
                font-size: 20px;
            }
        }

        @media (max-width: 320px) {
            #textarea {
                font-size: 18px;
            }

            button {
                height: 50px;
                font-size: 14px;
            }

            .btn {
                gap: 10px;
            }
        }

        /* Pulse animation for active calculations */
        .calculating {
            animation: pulse 0.5s ease-in-out;
        }

        @keyframes pulse {
            0% { box-shadow: 0 0 20px rgba(0, 255, 255, 0.2); }
            50% { box-shadow: 0 0 40px rgba(0, 255, 255, 0.6); }
            100% { box-shadow: 0 0 20px rgba(0, 255, 255, 0.2); }
        }