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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: linear-gradient(135deg, #1e3a8a 0%, #3b82f6 100%);
    color: white;
    padding: 2rem 0;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

header .subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* Navigation */
.category-nav {
    background-color: white;
    padding: 1rem 0;
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
    position: sticky;
    top: 0;
    z-index: 100;
}

.category-nav .container {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
}

.nav-btn {
    padding: 0.75rem 1.5rem;
    border: 2px solid #e5e7eb;
    background-color: white;
    color: #4b5563;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.nav-btn:hover {
    background-color: #f9fafb;
    border-color: #3b82f6;
    color: #3b82f6;
}

.nav-btn.active {
    background-color: #3b82f6;
    color: white;
    border-color: #3b82f6;
}

/* Main Content */
main {
    padding: 2rem 0;
}

.calculator-section {
    margin-bottom: 2rem;
}

.calculator-section h2 {
    color: #1e3a8a;
    font-size: 2rem;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 3px solid #3b82f6;
}

/* Calculator Cards */
.calculator-card {
    background: white;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.07);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.calculator-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.1);
}

.calculator-card h3 {
    color: #1e40af;
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.calculator-card > p {
    color: #6b7280;
    margin-bottom: 1.5rem;
    font-size: 1rem;
}

/* Forms */
.calculator-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.calculator-form h4 {
    color: #374151;
    font-size: 1.1rem;
    margin-top: 1rem;
    margin-bottom: 0.5rem;
}

.calculator-form label {
    color: #374151;
    font-weight: 500;
    font-size: 0.95rem;
}

.calculator-form input[type="number"],
.calculator-form input[type="date"],
.calculator-form select {
    padding: 0.75rem;
    border: 2px solid #e5e7eb;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
    width: 100%;
}

.calculator-form input[type="number"]:focus,
.calculator-form input[type="date"]:focus,
.calculator-form select:focus {
    outline: none;
    border-color: #3b82f6;
}

.calculator-form input[type="checkbox"] {
    width: auto;
    margin-right: 0.5rem;
}

.calculator-form small {
    color: #6b7280;
    font-size: 0.85rem;
    display: block;
    margin-top: -0.5rem;
}

.calculator-form button {
    padding: 1rem 2rem;
    background-color: #3b82f6;
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s ease;
    margin-top: 0.5rem;
}

.calculator-form button:hover {
    background-color: #2563eb;
}

.calculator-form button:active {
    transform: scale(0.98);
}

/* Results */
.result {
    margin-top: 1.5rem;
    padding: 1.5rem;
    background-color: #f0f9ff;
    border-left: 4px solid #3b82f6;
    border-radius: 8px;
    display: none;
}

.result.show {
    display: block;
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result h4 {
    color: #1e40af;
    font-size: 1.3rem;
    margin-bottom: 1rem;
}

.result p {
    color: #374151;
    margin-bottom: 0.5rem;
    font-size: 1rem;
}

.result strong {
    color: #1e40af;
}

.result .highlight {
    font-size: 1.5rem;
    color: #059669;
    font-weight: 700;
}

.result .warning {
    color: #dc2626;
    font-weight: 600;
}

.result .info {
    background-color: #dbeafe;
    padding: 1rem;
    border-radius: 6px;
    margin-top: 1rem;
}

/* Footer */
footer {
    background-color: #1f2937;
    color: white;
    padding: 2rem 0;
    text-align: center;
    margin-top: 3rem;
}

footer p {
    margin-bottom: 0.5rem;
}

footer a {
    color: #60a5fa;
    text-decoration: none;
    margin: 0 0.5rem;
}

footer a:hover {
    text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }

    header .subtitle {
        font-size: 1rem;
    }

    .nav-btn {
        padding: 0.5rem 1rem;
        font-size: 0.9rem;
    }

    .calculator-card {
        padding: 1.5rem;
    }

    .calculator-card h3 {
        font-size: 1.3rem;
    }

    .calculator-section h2 {
        font-size: 1.5rem;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.5rem;
    }

    .calculator-card {
        padding: 1rem;
    }

    .calculator-form button {
        font-size: 1rem;
        padding: 0.75rem 1.5rem;
    }
}

/* Print Styles */
@media print {
    .category-nav,
    footer {
        display: none;
    }

    .calculator-card {
        page-break-inside: avoid;
        box-shadow: none;
        border: 1px solid #e5e7eb;
    }
}