body {
            background: linear-gradient(135deg, #6a11cb 0%, #2575fc 100%);
            min-height: 100vh;
            display: flex;
            align-items: center;
            padding: 20px 0;
        }
        .calculator-card {
            background: rgba(255, 255, 255, 0.92);
            border-radius: 20px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
            overflow: hidden;
            max-width: 500px;
            margin: 0 auto;
        }
        .card-header {
            background: linear-gradient(to right, #3498db, #2c3e50);
            color: white;
            padding: 25px 20px;
            text-align: center;
        }
        .card-body {
            padding: 30px;
        }
        
        .input-group-text {
            background: #e9ecef;
        }
        #convertBtn {
            background: linear-gradient(to right, #3498db, #2c3e50);
            border: none;
            transition: all 0.3s;
            font-weight: 600;
            padding: 12px 0;
            margin: 15px 0;
        }
        #convertBtn:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
        }
        .result-box {
            background-color: #f8f9fa;
            border-radius: 5px;
            padding: 15px;
            margin-top: 20px;
            border-left: 4px solid #3498db;
        }
        .formula {
            background-color: #e3f2fd;
            border-radius: 8px;
            padding: 15px;
            margin-top: 25px;
            font-size: 0.9rem;
        }
        .formula-title {
            font-weight: 600;
            color: #2c3e50;
            margin-bottom: 8px;
        }
        .example {
            background-color: #e8f5e9;
            border-radius: 8px;
            padding: 15px;
            margin-top: 15px;
            font-size: 0.9rem;
        }
       
        .history-item {
            padding: 8px 12px;
            border-bottom: 1px solid #eee;
            font-size: 0.9rem;
        }
        .history-item:last-child {
            border-bottom: none;
        }