:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --success-color: #059669;
    --warning-color: #d97706;
    --error-color: #dc2626;
    --background: #ffffff;
    --surface: #f8fafc;
    --surface-hover: #f1f5f9;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 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);
}

[data-theme="dark"] {
    --background: #0f172a;
    --surface: #1e293b;
    --surface-hover: #334155;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --border: #334155;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.3), 0 1px 2px 0 rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.2);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--background);
    color: var(--text);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 24px;
}

header {
    text-align: center;
    margin-bottom: 48px;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 12px;
    color: var(--primary-color);
}

header p {
    color: var(--text-muted);
    font-size: 1.125rem;
}

.calculator-panel {
    background: var(--surface);
    border-radius: 16px;
    padding: 32px;
    border: 1px solid var(--border);
    box-shadow: var(--shadow-lg);
}

.input-section {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 24px;
    margin-bottom: 32px;
}

.input-group {
    display: flex;
    flex-direction: column;
}

.input-group label {
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text);
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 0.025em;
}

.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

.input-wrapper input {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    background: var(--background);
    color: var(--text);
    transition: border-color 0.2s, box-shadow 0.2s;
}

.input-wrapper input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.currency, .unit {
    position: absolute;
    font-weight: 600;
    color: var(--text-muted);
    font-size: 0.875rem;
    pointer-events: none;
}

.currency {
    left: 12px;
}

.unit {
    right: 12px;
}

.input-wrapper input:has(+ .unit) {
    padding-right: 40px;
}

.input-wrapper:has(.currency) input {
    padding-left: 32px;
}

.calculate-btn {
    grid-column: 1 / -1;
    padding: 16px 32px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.1s;
    text-transform: uppercase;
    letter-spacing: 0.025em;
}

.calculate-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

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

.results-section {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 32px;
}

.result-card {
    background: var(--background);
    border: 2px solid var(--border);
    border-radius: 12px;
    padding: 24px;
    text-align: center;
    transition: border-color 0.2s, transform 0.2s;
}

.result-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.result-card h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 0.025em;
}

.result-value {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--primary-color);
}

.chart-section {
    margin-bottom: 32px;
    text-align: center;
}

.chart-section canvas {
    max-width: 100%;
    border-radius: 8px;
    background: var(--background);
    border: 1px solid var(--border);
}

.schedule-section {
    border-top: 1px solid var(--border);
    padding-top: 32px;
}

.schedule-toggle {
    width: 100%;
    padding: 16px;
    background: var(--success-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s;
    margin-bottom: 24px;
}

.schedule-toggle:hover {
    background: #047857;
}

.schedule-table {
    overflow: hidden;
    transition: max-height 0.3s ease-out;
}

.schedule-table.hidden {
    max-height: 0;
}

.schedule-table:not(.hidden) {
    max-height: 600px;
    overflow-y: auto;
}

.table-wrapper {
    border-radius: 8px;
    border: 1px solid var(--border);
    overflow: hidden;
}

table {
    width: 100%;
    border-collapse: collapse;
    background: var(--background);
}

thead th {
    background: var(--surface);
    padding: 16px 12px;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text);
    text-align: right;
    border-bottom: 2px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 1;
}

thead th:first-child {
    text-align: center;
}

tbody td {
    padding: 12px;
    font-size: 0.875rem;
    border-bottom: 1px solid var(--border);
    text-align: right;
}

tbody td:first-child {
    text-align: center;
    font-weight: 600;
    color: var(--text-muted);
}

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

tfoot td {
    padding: 16px 12px;
    font-weight: 700;
    font-size: 0.875rem;
    border-top: 2px solid var(--border);
    background: var(--surface);
    text-align: right;
}

tfoot td:first-child {
    text-align: center;
    color: var(--text-muted);
}

.principal-amount {
    color: var(--primary-color);
    font-weight: 600;
}

.interest-amount {
    color: var(--warning-color);
    font-weight: 600;
}

.balance-amount {
    color: var(--text);
    font-weight: 500;
}

@media (max-width: 768px) {
    .container {
        padding: 16px;
    }
    
    header h1 {
        font-size: 2rem;
    }
    
    .calculator-panel {
        padding: 20px;
    }
    
    .input-section {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .results-section {
        grid-template-columns: 1fr;
        gap: 16px;
    }
    
    .result-value {
        font-size: 1.5rem;
    }
    
    .schedule-table:not(.hidden) {
        max-height: 400px;
    }
    
    .table-wrapper {
        font-size: 0.75rem;
    }
    
    thead th, tbody td, tfoot td {
        padding: 8px 6px;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.75rem;
    }
    
    .result-value {
        font-size: 1.25rem;
    }
    
    .table-wrapper {
        font-size: 0.7rem;
    }
}