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

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 20px;
        } */

        .container {
            background: white;
            border-radius: 16px;
            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
            max-width: 450px;
            width: 100%;
            overflow: hidden;
        }

        .header {
            background: #F2F8FF;
            color: white;
            padding: 30px;
            text-align: center;
        }

        .header h1 {
            font-size: 1.75rem;
            font-weight: 600;
            margin-bottom: 8px;
				
        }

        .header p {
            font-size: 0.95rem;
            opacity: 0.9;
					color:gray;
        }

        .card-body {
            padding: 30px;
        }

        .input-group {
            margin-bottom: 20px;
        }

        .input-group label {
            display: block;
            font-size: 0.9rem;
            font-weight: 500;
            color: #374151;
            margin-bottom: 8px;
        }

        .input-group input {
            width: 100%;
            padding: 14px 16px;
            border: 2px solid #e5e7eb;
            border-radius: 10px;
            font-size: 1rem;
            transition: all 0.3s ease;
            outline: none;
        }

        .input-group input:hover {
            border-color: #93c5fd;
        }

        .input-group input:focus {
            border-color: #3b82f6;
            box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.1);
        }

        .input-group input.error {
            border-color: #ef4444;
            background-color: #fef2f2;
        }

        .error-message {
            color: #ef4444;
            font-size: 0.85rem;
            margin-top: 6px;
            display: none;
        }

        .error-message.visible {
            display: block;
        }

        .result-section {
            background: linear-gradient(135deg, #eff6ff 0%, #dbeafe 100%);
            border-radius: 12px;
            padding: 25px;
            text-align: center;
            margin-top: 25px;
            border: 2px solid #bfdbfe;
        }

        .result-label {
            font-size: 0.9rem;
            color: #1e40af;
            font-weight: 500;
            margin-bottom: 10px;
        }

        .result-value {
            font-size: 3rem;
            font-weight: 700;
            color: #1e40af;
            line-height: 1;
        }

        .result-value.placeholder {
            color: #9ca3af;
            font-size: 1.5rem;
            font-weight: 400;
        }

        .formula-display {
            background: #f8fafc;
            border-radius: 8px;
            padding: 15px;
            margin-top: 20px;
            font-size: 0.85rem;
            color: #64748b;
            text-align: center;
            border: 1px solid #e2e8f0;
        }

        .formula-display strong {
            color: #1e40af;
        }

        .button-group {
            margin-top: 25px;
            display: flex;
            gap: 12px;
        }

        .btn {
            flex: 1;
            padding: 14px 20px;
            border-radius: 10px;
            font-size: 1rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            border: none;
        }

        .btn-reset {
            background: #f1f5f9;
            color: #475569;
        }

        .btn-reset:hover {
            background: #e2e8f0;
            transform: translateY(-2px);
        }

        .btn-reset:active {
            transform: translateY(0);
        }

        @media (max-width: 480px) {
            body {
                padding: 15px;
            }

            .header {
                padding: 25px 20px;
            }

            .header h1 {
                font-size: 1.5rem;
            }

            .card-body {
                padding: 25px 20px;
            }

            .result-value {
                font-size: 2.5rem;
            }

            .button-group {
                flex-direction: column;
            }
        }