* { margin: 0; padding: 0; box-sizing: border-box; }
        body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; background: linear-gradient(135deg, #f5f7fa 0%, #e4e8ec 100%); min-height: 100vh; color: #2d3748; }
        .container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }
        header { background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; padding: 20px 0; box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1); position: sticky; top: 0; z-index: 100; }
        .header-content { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 15px; }
        .logo { font-size: 24px; font-weight: 700; text-decoration: none; color: white; display: flex; align-items: center; gap: 10px; }
        nav ul { display: flex; list-style: none; gap: 25px; }
        nav a { color: white; text-decoration: none; font-weight: 600; display: flex; align-items: center; gap: 5px; }
        .breadcrumb { background: white; padding: 15px 0; border-bottom: 1px solid #e2e8f0; }
        .breadcrumb-list { display: flex; align-items: center; gap: 10px; list-style: none; margin: 0; padding: 0; font-size: 14px; color: #718096; }
        .breadcrumb-list li { display: flex; align-items: center; }
        .breadcrumb-list a { color: #667eea; text-decoration: none; }
        .breadcrumb-list li::after { content: '/'; margin-left: 10px; color: #cbd5e0; }
        .breadcrumb-list li:last-child::after { display: none; }
        .main-content { padding: 40px 0; }
        .tool-section { background: white; border-radius: 20px; padding: 40px; box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08); margin-bottom: 40px; }
        .tool-header { text-align: center; margin-bottom: 40px; }
        .tool-header h1 { font-size: 32px; color: #2d3748; margin-bottom: 10px; }
        .tool-header h1 i { color: #667eea; margin-right: 10px; }
        .tool-header p { color: #718096; font-size: 16px; }
        .calculator-box { max-width: 400px; margin: 0 auto; }
        .calc-display { background: linear-gradient(135deg, #2d3748 0%, #1a202c 100%); border-radius: 15px; padding: 20px; margin-bottom: 20px; }
        .calc-history { color: #a0aec0; font-size: 14px; min-height: 20px; text-align: right; margin-bottom: 5px; }
        .calc-result { color: white; font-size: 36px; text-align: right; font-weight: 600; word-break: break-all; }
        .calc-buttons { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; }
        .calc-btn { padding: 20px; font-size: 20px; border: none; border-radius: 12px; cursor: pointer; transition: all 0.2s; font-weight: 600; }
        .calc-btn:hover { transform: translateY(-2px); }
        .calc-btn:active { transform: translateY(0); }
        .calc-btn.number { background: #f7fafc; color: #2d3748; }
        .calc-btn.number:hover { background: #edf2f7; }
        .calc-btn.operator { background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; }
        .calc-btn.operator:hover { box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4); }
        .calc-btn.function { background: #edf2f7; color: #667eea; }
        .calc-btn.function:hover { background: #e2e8f0; }
        .calc-btn.clear { background: #fed7d7; color: #c53030; }
        .calc-btn.clear:hover { background: #feb2b2; }
        .calc-btn.equals { background: linear-gradient(135deg, #48bb78 0%, #38a169 100%); color: white; }
        .calc-btn.equals:hover { box-shadow: 0 5px 15px rgba(72, 187, 120, 0.4); }
        .calc-btn.zero { grid-column: span 2; }
        .info-section { background: white; border-radius: 15px; padding: 30px; box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05); }
        .info-section h2 { font-size: 20px; color: #2d3748; margin-bottom: 20px; display: flex; align-items: center; gap: 10px; }
        .info-section h2 i { color: #667eea; }
        .info-section p { color: #4a5568; margin-bottom: 15px; line-height: 1.8; }
        .info-section ul { margin-left: 20px; color: #4a5568; }
        .info-section li { margin-bottom: 10px; line-height: 1.8; }
        footer { background: #2d3748; color: #a0aec0; padding: 40px 0 20px; margin-top: 60px; }
        .footer-content { text-align: center; }
        .footer-links { display: flex; justify-content: center; gap: 20px; margin-bottom: 20px; flex-wrap: wrap; }
        .footer-links a { color: #a0aec0; text-decoration: none; }
        .copyright { font-size: 14px; color: #718096; }
        @media (max-width: 768px) {
            .header-content { flex-direction: column; text-align: center; }
            nav ul { flex-wrap: wrap; justify-content: center; }
            .tool-section { padding: 25px 15px; }
            .tool-header h1 { font-size: 24px; }
            .calc-btn { padding: 15px; font-size: 18px; }
        }