/* CSS Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #1e40af;
    --primary-dark: #1e3a8a;
    --secondary-color: #3b82f6;
    --accent-color: #10b981;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --border-color: #e5e7eb;
    --error-color: #ef4444;
    --success-color: #10b981;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-secondary);
}

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

/* Header Styles */
header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 3rem 0;
    text-align: center;
    box-shadow: var(--shadow-lg);
}

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

.subtitle {
    font-size: 1.2rem;
    opacity: 0.95;
    font-weight: 400;
}

/* Main Content */
main {
    padding: 3rem 0;
}

.calculator-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-bottom: 3rem;
}

/* Calculator Form */
.calculator-form {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
}

.calculator-form h2 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    font-size: 1.75rem;
}

.form-group {
    margin-bottom: 1.5rem;
}

label {
    display: block;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    font-size: 0.95rem;
}

.tooltip {
    display: inline-block;
    margin-left: 0.5rem;
    color: var(--secondary-color);
    cursor: help;
    font-size: 0.85rem;
}

.helper-text {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

input[type="number"],
select {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

input[type="number"]:focus,
select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(30, 64, 175, 0.1);
}

.term-selector {
    display: flex;
    gap: 0.5rem;
}

.term-selector input {
    flex: 1;
}

.term-selector select {
    flex: 0 0 120px;
}

.form-actions {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
}

.btn-primary,
.btn-secondary {
    padding: 0.875rem 2rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    flex: 1;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-secondary {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--border-color);
}

/* Results Section */
.calculator-results {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
}

.results-placeholder {
    text-align: center;
    color: var(--text-secondary);
}

.results-placeholder h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.result-card {
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    border-left: 4px solid var(--primary-color);
    padding: 1.5rem;
    border-radius: 8px;
    margin-bottom: 1rem;
}

.result-label {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.result-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
}

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

.result-footer {
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    font-size: 0.9rem;
}

.total-repayment {
    font-weight: 600;
    color: var(--text-primary);
}

/* Amortization Schedule */
.amortization-schedule {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 3rem;
}

.amortization-schedule.hidden {
    display: none;
}

.schedule-controls {
    margin-bottom: 1rem;
}

.amortization-table {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1rem;
}

thead {
    background: var(--primary-color);
    color: white;
}

th, td {
    padding: 0.75rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

th {
    font-weight: 600;
    font-size: 0.9rem;
}

tbody tr:hover {
    background: var(--bg-secondary);
}

.summary-row {
    font-weight: 600;
    background: var(--bg-secondary);
}

/* Chart Section */
.chart-section {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 3rem;
}

.chart-section.hidden {
    display: none;
}

#paymentChart {
    height: 400px;
    margin-top: 1rem;
}

/* SEO Content Section */
.seo-content {
    background: var(--bg-primary);
    padding: 4rem 0;
    margin: 3rem 0;
}

.seo-content h2 {
    color: var(--primary-color);
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.seo-content h3 {
    color: var(--primary-color);
    font-size: 1.5rem;
    margin-top: 2rem;
    margin-bottom: 1rem;
}

.seo-content p {
    margin-bottom: 1.5rem;
    line-height: 1.8;
    color: var(--text-primary);
}

.seo-content ul,
.seo-content ol {
    margin-left: 2rem;
    margin-bottom: 1.5rem;
}

.seo-content li {
    margin-bottom: 0.75rem;
    line-height: 1.7;
}

.seo-content strong {
    color: var(--primary-color);
}

/* Footer */
footer {
    background: var(--text-primary);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

.footer-content p {
    margin-bottom: 0.5rem;
}

.footer-content a {
    color: var(--secondary-color);
    text-decoration: none;
}

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

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.75rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .calculator-container {
        grid-template-columns: 1fr;
    }
    
    .form-actions {
        flex-direction: column;
    }
    
    .result-value {
        font-size: 1.75rem;
    }
    
    .result-value-large {
        font-size: 2rem;
    }
    
    table {
        font-size: 0.875rem;
    }
    
    th, td {
        padding: 0.5rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }
    
    header {
        padding: 2rem 0;
    }
    
    main {
        padding: 2rem 0;
    }
    
    .calculator-form,
    .calculator-results,
    .amortization-schedule,
    .chart-section {
        padding: 1.5rem;
    }
    
    .term-selector {
        flex-direction: column;
    }
    
    .term-selector select {
        flex: 1;
    }
}

/* Accessibility */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-card,
.amortization-schedule,
.chart-section {
    animation: fadeIn 0.5s ease-in;
}

/* Print Styles */
@media print {
    .calculator-form,
    .form-actions,
    footer {
        display: none;
    }
    
    .calculator-results,
    .amortization-schedule,
    .chart-section {
        break-inside: avoid;
    }
}