:root {
    /* Color Palette */
    --bg-white: #FFFFFF;
    --bg-warm-gray: #FAFAFA;
    --text-primary: #111827;
    --text-secondary: #6B7280;
    --text-accent: #000000;
    --border-light: #E5E7EB;
    
    /* Buttons */
    --btn-primary-bg: #000000;
    --btn-primary-text: #FFFFFF;
    --btn-primary-hover: #1F2937;

    /* Highlight Green for Positive financial outcome */
    --text-green: #059669;
    --bg-green-light: #ECFDF5;

    /* Metrics */
    --radius-sm: 8px;
    --radius-md: 12px;
    --font-inter: 'Inter', system-ui, -apple-system, sans-serif;
}

/* Reset & Base Values */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-inter);
    background-color: var(--bg-white);
    color: var(--text-primary);
    line-height: 1.6;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Utilities */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 24px;
}

.text-center {
    text-align: center;
}

/* Typography */
h1 {
    font-size: 48px;
    line-height: 1.1;
    letter-spacing: -0.02em;
    font-weight: 700;
}

h2 {
    font-size: 32px;
    line-height: 1.2;
    font-weight: 600;
}

h3 {
    font-size: 20px;
    font-weight: 600;
}

a {
    color: var(--text-primary);
    text-decoration: none;
    transition: color 0.15s ease;
}

a:hover {
    color: var(--text-secondary);
}

/* Navbar */
.navbar {
    border-bottom: 1px solid var(--border-light);
    padding: 24px 0;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(8px);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.brand {
    font-weight: 700;
    font-size: 20px;
    letter-spacing: -0.01em;
}

.nav-links {
    display: flex;
    gap: 24px;
}

.nav-link {
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
}

.nav-link:hover, .nav-link.active {
    color: var(--text-primary);
}

/* Hero */
.hero {
    padding: 80px 0 64px;
}

.hero-subtitle {
    margin-top: 16px;
    font-size: 18px;
    color: var(--text-secondary);
    max-width: 500px;
    margin-inline: auto;
}

/* Calculator Grid */
.calculator-section {
    padding-bottom: 64px;
}

.calc-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}

.card {
    background-color: var(--bg-white);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    padding: 32px;
    transition: box-shadow 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.card:hover {
    box-shadow: 0 4px 14px rgba(0,0,0,0.06);
}

.card-title {
    font-size: 20px;
    margin-bottom: 24px;
}

/* Inputs */
.form-group {
    margin-bottom: 24px;
    display: flex;
    flex-direction: column;
}

.form-group label {
    font-size: 14px;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.label-optional {
    display: block;
    font-size: 12px;
    font-weight: 400;
    color: var(--text-secondary);
    margin-top: 2px;
}

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

.input-prefix .prefix {
    position: absolute;
    left: 16px;
    color: var(--text-secondary);
    font-weight: 500;
}

input[type="number"], select {
    width: 100%;
    background-color: var(--bg-warm-gray);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-sm);
    padding: 12px 16px;
    font-family: var(--font-inter);
    font-size: 16px;
    color: var(--text-primary);
    transition: all 0.2s ease;
    -moz-appearance: textfield;
}

.input-prefix input {
    padding-left: 32px;
}

input[type="number"]:focus, select:focus {
    outline: none;
    box-shadow: 0 0 0 2px var(--bg-white), 0 0 0 4px var(--text-primary);
    background-color: var(--bg-white);
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

/* Toggle Switch */
.toggle-group {
    display: flex;
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    margin-top: 32px;
    padding-top: 24px;
    border-top: 1px solid var(--border-light);
}

.toggle-label {
    margin-bottom: 0 !important;
    display: flex;
    flex-direction: column;
}

.toggle-text {
    font-weight: 500;
}

.toggle-subtext {
    font-size: 12px;
    color: var(--text-secondary);
    font-weight: 400;
    margin-top: 2px;
}

.switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
    flex-shrink: 0;
}

.switch input { 
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: var(--border-light);
    transition: .3s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 20px;
    width: 20px;
    left: 2px;
    bottom: 2px;
    background-color: white;
    transition: .3s;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

input:checked + .slider {
    background-color: var(--text-primary);
}

input:checked + .slider:before {
    transform: translateX(20px);
}

.slider.round {
    border-radius: 24px;
}

.slider.round:before {
    border-radius: 50%;
}

/* Output Data */
.output-card {
    background-color: var(--bg-warm-gray);
    display: flex;
    flex-direction: column;
}

.result-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 0;
}

.result-label {
    color: var(--text-secondary);
    font-size: 15px;
}

.result-value {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
}

.highlight-green .result-label, .highlight-green .result-value {
    color: var(--text-green);
}

.result-divider {
    height: 1px;
    background-color: var(--border-light);
    margin: 8px 0;
}

.total-row .result-value {
    font-size: 28px;
    letter-spacing: -0.01em;
}

.total-row .result-label {
    font-weight: 500;
    color: var(--text-primary);
}

.yearly-summary {
    margin-top: auto;
    padding-top: 32px;
    font-size: 14px;
    color: var(--text-secondary);
}

.yearly-summary strong {
    color: var(--text-primary);
}

.limit-warning {
    margin-top: 8px;
    color: #B45309; /* warm orange/amber */
    background-color: #FEF3C7;
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: flex-start;
    gap: 8px;
    font-size: 13px;
    font-weight: 500;
}

.limit-warning svg {
    flex-shrink: 0;
    margin-top: 2px;
}

/* Info Sections */
.info-section {
    padding: 64px 0;
    border-top: 1px solid var(--border-light);
}

.hero-year {
    display: inline-block;
    font-size: 20px;
    font-weight: 600;
    color: var(--text-secondary);
    vertical-align: super;
    letter-spacing: 0;
}

/* About / SEO Content */
.about-content {
    max-width: 640px;
    margin: 0 auto;
}

.about-content p {
    font-size: 15px;
    color: var(--text-secondary);
    line-height: 1.75;
    margin-bottom: 16px;
}

.about-content h3 {
    font-size: 17px;
    font-weight: 600;
    color: var(--text-primary);
    margin-top: 32px;
    margin-bottom: 12px;
}

.about-content ul {
    list-style: none;
    padding: 0;
}

.about-content ul li {
    font-size: 15px;
    color: var(--text-secondary);
    line-height: 1.75;
    padding: 6px 0 6px 20px;
    position: relative;
}

.about-content ul li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 14px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--text-green);
}

.about-content a {
    color: var(--text-green);
    text-decoration: underline;
    text-underline-offset: 2px;
}

.about-content a:hover {
    color: var(--text-primary);
}

.section-title {
    margin-bottom: 40px;
}

.steps-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.step-card {
    padding: 24px;
    background: var(--bg-warm-gray);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-light);
}

.step-num {
    width: 32px;
    height: 32px;
    background: var(--text-primary);
    color: var(--bg-white);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 14px;
    margin-bottom: 16px;
}

.step-card h3 {
    font-size: 16px;
    margin-bottom: 8px;
}

.step-card p {
    font-size: 14px;
    color: var(--text-secondary);
}

/* FAQ Accordion */
.faq-accordion {
    max-width: 600px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid var(--border-light);
}

.faq-btn {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 24px 0;
    background: none;
    border: none;
    font-size: 16px;
    font-weight: 500;
    color: var(--text-primary);
    cursor: pointer;
    font-family: var(--font-inter);
    transition: color 0.2s ease;
}

.faq-btn:hover {
    color: var(--text-secondary);
}

.icon-chevron {
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.faq-btn[aria-expanded="true"] .icon-chevron {
    transform: rotate(180deg);
}

.faq-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.faq-content p {
    padding-bottom: 24px;
    color: var(--text-secondary);
    font-size: 15px;
}

/* Footer */
.footer {
    border-top: 1px solid var(--border-light);
    padding: 64px 0 32px;
    background-color: var(--bg-warm-gray);
}

.footer-content {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 40px;
    margin-bottom: 64px;
}

.footer-brand p {
    color: var(--text-secondary);
    font-size: 14px;
    margin-top: 8px;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 32px;
}

.link-col h4 {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.link-col a {
    display: block;
    color: var(--text-secondary);
    font-size: 14px;
    margin-bottom: 12px;
}

.link-col a:hover {
    color: var(--text-primary);
}

.footer-bottom {
    border-top: 1px solid var(--border-light);
    padding-top: 32px;
    font-size: 12px;
    color: var(--text-secondary);
    text-align: center;
}

.footer-bottom a {
    text-decoration: underline;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    h1 { font-size: 36px; }
    h2 { font-size: 24px; }
    
    .calc-grid {
        grid-template-columns: 1fr;
    }
    
    .steps-grid {
        grid-template-columns: 1fr;
    }

    .hero {
        padding: 40px 0;
    }

    .footer-content {
        grid-template-columns: 1fr;
    }

    .nav-links {
        display: none; /* simple mobile nav */
    }
}