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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --background-color: #f1f5f9;
    --card-background: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    text-align: center;
    margin-bottom: 30px;
    padding-top: 20px;
}

header h1 {
    font-size: 2.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 8px;
}

header .subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

main {
    flex: 1;
}

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

.form-group {
    margin-bottom: 24px;
}

.form-group label {
    display: block;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
    font-size: 0.95rem;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 14px 16px;
    font-size: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    transition: border-color 0.2s, box-shadow 0.2s;
    background: var(--card-background);
}

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

.form-group input::placeholder {
    color: var(--text-secondary);
}

.term-input-group {
    display: flex;
    gap: 12px;
}

.term-input-group input {
    flex: 2;
}

.term-input-group select {
    flex: 1;
    cursor: pointer;
}

.calculate-btn {
    width: 100%;
    padding: 16px;
    font-size: 1.1rem;
    font-weight: 600;
    color: white;
    background: var(--primary-color);
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.1s;
}

.calculate-btn:hover {
    background: var(--primary-hover);
}

.calculate-btn:active {
    transform: scale(0.98);
}

.results {
    margin-top: 32px;
    padding-top: 32px;
    border-top: 2px solid var(--border-color);
    animation: fadeIn 0.3s ease-out;
}

.results.hidden {
    display: none;
}

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

.results h2 {
    font-size: 1.5rem;
    margin-bottom: 24px;
    color: var(--text-primary);
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
    margin-bottom: 32px;
}

.result-item {
    background: var(--background-color);
    padding: 20px;
    border-radius: 12px;
    text-align: center;
}

.result-label {
    display: block;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.result-value {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.result-item:first-child .result-value {
    color: var(--success-color);
    font-size: 1.75rem;
}

.payment-breakdown {
    background: var(--background-color);
    padding: 24px;
    border-radius: 12px;
}

.payment-breakdown h3 {
    font-size: 1rem;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.progress-bar {
    height: 24px;
    background: var(--border-color);
    border-radius: 12px;
    overflow: hidden;
    display: flex;
    margin-bottom: 16px;
}

.progress-principal {
    background: var(--primary-color);
    height: 100%;
    transition: width 0.5s ease-out;
}

.progress-interest {
    background: #f59e0b;
    height: 100%;
    transition: width 0.5s ease-out;
}

.breakdown-legend {
    display: flex;
    justify-content: center;
    gap: 24px;
    flex-wrap: wrap;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.legend-color {
    width: 14px;
    height: 14px;
    border-radius: 4px;
}

.principal-color {
    background: var(--primary-color);
}

.interest-color {
    background: #f59e0b;
}

footer {
    text-align: center;
    padding: 24px 0;
    margin-top: 40px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s;
}

footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Mobile Responsive Styles */
@media (max-width: 640px) {
    .container {
        padding: 16px;
    }

    header {
        margin-bottom: 24px;
        padding-top: 10px;
    }

    header h1 {
        font-size: 1.75rem;
    }

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

    .calculator-card {
        padding: 24px 20px;
        border-radius: 12px;
    }

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

    .form-group input,
    .form-group select {
        padding: 12px 14px;
    }

    .term-input-group {
        flex-direction: column;
        gap: 10px;
    }

    .term-input-group input,
    .term-input-group select {
        flex: none;
    }

    .results-grid {
        grid-template-columns: 1fr;
        gap: 12px;
    }

    .result-item {
        padding: 16px;
    }

    .result-value {
        font-size: 1.35rem;
    }

    .result-item:first-child .result-value {
        font-size: 1.5rem;
    }

    .breakdown-legend {
        gap: 16px;
    }

    .calculate-btn {
        padding: 14px;
        font-size: 1rem;
    }
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --background-color: #0f172a;
        --card-background: #1e293b;
        --text-primary: #f1f5f9;
        --text-secondary: #94a3b8;
        --border-color: #334155;
    }

    .form-group input,
    .form-group select {
        background: #0f172a;
        color: var(--text-primary);
    }

    .progress-bar {
        background: #334155;
    }
}