/* =========================================
   Option Value Calculator
   FT/Economist-Inspired Design System
   ========================================= */

/* CSS Custom Properties */
:root {
    /* Colors - FT-inspired palette */
    --color-background: #FFF8F0;
    --color-background-alt: #FFF1E5;
    --color-surface: #FFFFFF;
    --color-text: #1A1A1A;
    --color-text-secondary: #4A4A4A;
    --color-text-muted: #707070;
    --color-accent: #990F3D;
    --color-accent-light: #CC1B53;
    --color-positive: #0D7680;
    --color-positive-light: #0F9DA8;
    --color-negative: #990F3D;
    --color-border: #E0D8D0;
    --color-border-light: #EBE5DE;

    /* Typography */
    --font-serif: 'Libre Baskerville', Georgia, 'Times New Roman', serif;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    --space-4xl: 6rem;

    /* Layout */
    --max-width: 1200px;
    --content-width: 800px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-serif);
    font-weight: 700;
    line-height: 1.2;
    color: var(--color-text);
}

h1 { font-size: clamp(2.5rem, 5vw, 4rem); }
h2 { font-size: clamp(1.75rem, 3vw, 2.5rem); }
h3 { font-size: clamp(1.25rem, 2vw, 1.5rem); }

p {
    margin-bottom: var(--space-md);
}

a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-accent-light);
}

em {
    font-style: italic;
}

/* Layout */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-xl);
}

.section {
    padding: var(--space-4xl) 0;
}

/* Header */
.header {
    position: sticky;
    top: 0;
    background: var(--color-background);
    border-bottom: 1px solid var(--color-border-light);
    z-index: 100;
    padding: var(--space-md) 0;
}

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

.logo {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-text);
    letter-spacing: -0.02em;
}

.nav {
    display: flex;
    gap: var(--space-xl);
}

.nav a {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

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

/* Hero Section */
.hero {
    padding: var(--space-4xl) 0;
    min-height: 80vh;
    display: flex;
    align-items: center;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-4xl);
    align-items: center;
}

.hero-kicker {
    font-size: 0.875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-accent);
    margin-bottom: var(--space-md);
}

.hero-headline {
    margin-bottom: var(--space-lg);
    letter-spacing: -0.02em;
}

.hero-subhead {
    font-size: 1.25rem;
    line-height: 1.7;
    color: var(--color-text-secondary);
    margin-bottom: var(--space-xl);
    max-width: 540px;
}

.hero-cta {
    display: inline-block;
    padding: var(--space-md) var(--space-xl);
    background: var(--color-text);
    color: var(--color-background);
    font-weight: 600;
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    border-radius: 2px;
    transition: all var(--transition-base);
}

.hero-cta:hover {
    background: var(--color-accent);
    color: white;
}

.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.option-tree {
    width: 100%;
    max-width: 400px;
    height: auto;
    color: var(--color-text);
}

/* Section Headers */
.section-header {
    margin-bottom: var(--space-3xl);
}

.section-number {
    display: block;
    font-family: var(--font-serif);
    font-size: 0.875rem;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
}

.section-title {
    max-width: 700px;
}

/* Problem Section */
.section-problem {
    background: var(--color-surface);
    border-top: 1px solid var(--color-border-light);
    border-bottom: 1px solid var(--color-border-light);
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.problem-card {
    padding: var(--space-xl);
    border: 1px solid var(--color-border-light);
    border-radius: 2px;
    transition: border-color var(--transition-base);
}

.problem-card:hover {
    border-color: var(--color-border);
}

.problem-icon {
    width: 48px;
    height: 48px;
    margin-bottom: var(--space-lg);
    color: var(--color-accent);
}

.problem-icon svg {
    width: 100%;
    height: 100%;
}

.problem-card h3 {
    font-size: 1.125rem;
    margin-bottom: var(--space-md);
}

.problem-card p {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    margin-bottom: 0;
}

/* Theory Section */
.theory-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-4xl);
    margin-bottom: var(--space-3xl);
}

.theory-text {
    max-width: 500px;
}

.theory-lead {
    font-size: 1.125rem;
    line-height: 1.8;
    margin-bottom: var(--space-lg);
}

.theory-text p {
    color: var(--color-text-secondary);
}

.formula-box {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    padding: var(--space-xl);
    border-radius: 2px;
}

.formula-label {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-text-muted);
    margin-bottom: var(--space-md);
}

.formula {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    padding: var(--space-lg) 0;
    border-bottom: 1px solid var(--color-border-light);
    margin-bottom: var(--space-lg);
}

.formula sub {
    font-size: 0.75em;
}

.formula-terms {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-md);
}

.term {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.term-symbol {
    font-family: var(--font-serif);
    font-size: 0.875rem;
    font-weight: 700;
}

.term-desc {
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

/* Theory Types Grid */
.theory-types {
    margin-bottom: var(--space-3xl);
}

.theory-types h3 {
    font-size: 1.25rem;
    margin-bottom: var(--space-xl);
}

.types-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-lg);
}

.type-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border-light);
    padding: var(--space-lg);
    border-radius: 2px;
}

.type-icon {
    width: 40px;
    height: 40px;
    margin-bottom: var(--space-md);
    color: var(--color-text);
}

.type-icon svg {
    width: 100%;
    height: 100%;
}

.type-card h4 {
    font-family: var(--font-sans);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
    color: var(--color-positive);
}

.type-card p {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    margin-bottom: 0;
    line-height: 1.5;
}

@media (max-width: 1024px) {
    .types-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .types-grid {
        grid-template-columns: 1fr;
    }
}

.theory-insight {
    max-width: var(--content-width);
    margin: 0 auto;
    text-align: center;
}

.theory-insight blockquote {
    font-family: var(--font-serif);
    font-size: 1.5rem;
    font-style: italic;
    line-height: 1.6;
    color: var(--color-text-secondary);
    position: relative;
    padding: var(--space-xl) 0;
}

.theory-insight blockquote::before,
.theory-insight blockquote::after {
    content: '';
    display: block;
    width: 60px;
    height: 1px;
    background: var(--color-border);
    margin: 0 auto var(--space-xl);
}

.theory-insight blockquote::after {
    margin: var(--space-xl) auto 0;
}

.theory-insight em {
    color: var(--color-text);
    font-style: italic;
}

/* AI Shift Section */
.section-shift {
    background: var(--color-surface);
    border-top: 1px solid var(--color-border-light);
    border-bottom: 1px solid var(--color-border-light);
}

.shift-content {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: var(--space-xl);
    align-items: center;
    margin-bottom: var(--space-3xl);
}

.shift-before,
.shift-after {
    padding: var(--space-xl);
    border-radius: 2px;
}

.shift-before {
    background: var(--color-background);
    border: 1px solid var(--color-border);
}

.shift-after {
    background: linear-gradient(135deg, #E8F4F4, #F0FAF5);
    border: 1px solid var(--color-positive);
}

.shift-before h3,
.shift-after h3 {
    font-size: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--space-lg);
}

.shift-list {
    list-style: none;
    margin-bottom: var(--space-lg);
}

.shift-list li {
    padding: var(--space-sm) 0;
    padding-left: var(--space-lg);
    position: relative;
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
}

.shift-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 6px;
    height: 6px;
    background: var(--color-border);
    border-radius: 50%;
}

.shift-after .shift-list li::before {
    background: var(--color-positive);
}

.shift-verdict {
    font-weight: 600;
    font-size: 0.875rem;
    padding: var(--space-sm) var(--space-md);
    border-radius: 2px;
    display: inline-block;
}

.shift-verdict.negative {
    background: rgba(153, 15, 61, 0.1);
    color: var(--color-negative);
}

.shift-verdict.positive {
    background: rgba(13, 118, 128, 0.1);
    color: var(--color-positive);
}

.shift-arrow {
    width: 48px;
    height: 48px;
    color: var(--color-text-muted);
}

.shift-arrow svg {
    width: 100%;
    height: 100%;
}

.shift-implications h3 {
    text-align: center;
    margin-bottom: var(--space-xl);
}

.implications-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.implication {
    text-align: center;
    padding: var(--space-xl);
}

.implication-number {
    display: block;
    font-family: var(--font-serif);
    font-size: 3rem;
    font-weight: 700;
    color: var(--color-positive);
    line-height: 1;
    margin-bottom: var(--space-sm);
}

.implication-text {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

/* Calculator Section */
.section-calculator {
    background: var(--color-background-alt);
}

.calculator-intro {
    max-width: 600px;
    font-size: 1.125rem;
    color: var(--color-text-secondary);
    margin-bottom: var(--space-3xl);
}

.calculator-wrapper {
    display: grid;
    grid-template-columns: 400px 1fr;
    gap: var(--space-3xl);
}

.calculator-inputs {
    display: flex;
    flex-direction: column;
    gap: var(--space-xl);
}

.input-group {
    background: var(--color-surface);
    padding: var(--space-lg);
    border: 1px solid var(--color-border-light);
    border-radius: 2px;
}

.input-group label {
    display: block;
    margin-bottom: var(--space-md);
}

.input-label {
    display: block;
    font-weight: 600;
    font-size: 0.875rem;
    margin-bottom: var(--space-xs);
}

.input-help {
    display: block;
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

input[type="range"] {
    width: 100%;
    height: 4px;
    background: var(--color-border);
    border-radius: 2px;
    appearance: none;
    cursor: pointer;
    margin-bottom: var(--space-sm);
}

input[type="range"]::-webkit-slider-thumb {
    appearance: none;
    width: 20px;
    height: 20px;
    background: var(--color-text);
    border-radius: 50%;
    cursor: pointer;
    transition: transform var(--transition-fast);
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.1);
}

input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    background: var(--color-text);
    border-radius: 50%;
    border: none;
    cursor: pointer;
}

.input-value {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

.input-value span {
    font-weight: 600;
    color: var(--color-text);
}

/* Calculator Outputs */
.calculator-outputs {
    display: flex;
    flex-direction: column;
    gap: var(--space-xl);
}

.output-primary {
    margin-bottom: var(--space-md);
}

.output-card {
    background: var(--color-surface);
    padding: var(--space-lg);
    border: 1px solid var(--color-border-light);
    border-radius: 2px;
}

.output-card.highlight {
    background: var(--color-text);
    color: var(--color-background);
    border: none;
    padding: var(--space-xl);
}

.output-card.highlight .output-label {
    color: rgba(255, 255, 255, 0.7);
}

.output-card.highlight .output-value {
    color: var(--color-background);
    font-size: 3rem;
}

.output-card.highlight .output-context {
    color: rgba(255, 255, 255, 0.6);
}

.output-label {
    display: block;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-muted);
    margin-bottom: var(--space-sm);
}

.output-value {
    display: block;
    font-family: var(--font-serif);
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: var(--space-xs);
}

.output-context {
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

.output-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-md);
}

.chart-container {
    background: var(--color-surface);
    border: 1px solid var(--color-border-light);
    border-radius: 2px;
    padding: var(--space-xl);
    height: 300px;
}

/* Case Studies Section */
.cases-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.case-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border-light);
    border-radius: 2px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.case-header {
    padding: var(--space-lg);
    border-bottom: 1px solid var(--color-border-light);
}

.case-category {
    display: block;
    font-size: 0.6875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
}

.case-header h3 {
    font-size: 1.125rem;
    line-height: 1.4;
}

.case-body {
    padding: var(--space-lg);
    flex: 1;
}

.case-body p {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: var(--space-lg);
}

.case-metrics {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-sm);
}

.metric {
    text-align: center;
}

.metric-value {
    display: block;
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-positive);
    margin-bottom: var(--space-xs);
}

.metric-label {
    font-size: 0.6875rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.case-footer {
    padding: var(--space-md) var(--space-lg);
    background: var(--color-background);
    border-top: 1px solid var(--color-border-light);
}

.case-result {
    font-size: 0.8125rem;
    font-weight: 600;
}

.case-result.positive {
    color: var(--color-positive);
}

/* References Section */
.section-references {
    background: var(--color-surface);
    border-top: 1px solid var(--color-border-light);
}

/* CTA Section */
.section-cta {
    background: var(--color-background-alt);
    border-top: 1px solid var(--color-border-light);
}

.cta-content {
    display: grid;
    grid-template-columns: 1.3fr 0.7fr;
    gap: var(--space-3xl);
    align-items: center;
}

.cta-kicker {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-accent);
    margin-bottom: var(--space-md);
}

.cta-text h2 {
    margin-bottom: var(--space-lg);
}

.cta-text p {
    font-size: 1rem;
    color: var(--color-text-secondary);
    margin-bottom: 0;
}

.cta-actions {
    background: var(--color-surface);
    border: 1px solid var(--color-border-light);
    padding: var(--space-xl);
    border-radius: 2px;
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.cta-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-md) var(--space-lg);
    background: var(--color-text);
    color: var(--color-background);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    border-radius: 2px;
    transition: background var(--transition-base);
}

.cta-button:hover {
    background: var(--color-accent);
    color: white;
}

.cta-note {
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

.references-intro {
    max-width: 700px;
    font-size: 1.125rem;
    color: var(--color-text-secondary);
    margin-bottom: var(--space-3xl);
}

.references-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
    max-width: 800px;
}

.reference {
    padding-bottom: var(--space-lg);
    border-bottom: 1px solid var(--color-border-light);
}

.reference:last-child {
    border-bottom: none;
}

.reference-authors {
    font-weight: 600;
    font-size: 0.9375rem;
}

.reference-year {
    color: var(--color-text-muted);
    font-size: 0.875rem;
    margin-left: var(--space-sm);
}

.reference-title {
    display: block;
    font-family: var(--font-serif);
    font-style: italic;
    font-size: 1rem;
    margin: var(--space-xs) 0;
}

.reference-source {
    display: block;
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

/* Footer */
.footer {
    background: var(--color-text);
    color: var(--color-background);
    padding: var(--space-3xl) 0 var(--space-xl);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--space-3xl);
}

.footer-brand .logo {
    color: var(--color-background);
    display: block;
    margin-bottom: var(--space-sm);
}

.footer-brand p {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.6);
    margin-bottom: 0;
}

.footer-links {
    display: flex;
    gap: var(--space-xl);
}

.footer-links a {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.7);
}

.footer-links a:hover {
    color: var(--color-background);
}

.footer-bottom {
    padding-top: var(--space-xl);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    font-size: 0.8125rem;
    color: rgba(255, 255, 255, 0.5);
    margin-bottom: 0;
}

/* Responsive Design */
@media (max-width: 1024px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-subhead {
        max-width: 100%;
        margin-left: auto;
        margin-right: auto;
    }

    .hero-visual {
        order: -1;
        margin-bottom: var(--space-xl);
    }

    .option-tree {
        max-width: 300px;
    }

    .problem-grid,
    .implications-grid,
    .cases-grid {
        grid-template-columns: 1fr;
    }

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

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

    .shift-arrow {
        transform: rotate(90deg);
        margin: 0 auto;
    }

    .calculator-wrapper {
        grid-template-columns: 1fr;
    }

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

    .output-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav {
        display: none;
    }

    .section {
        padding: var(--space-3xl) 0;
    }

    .container {
        padding: 0 var(--space-md);
    }

    .formula-terms {
        grid-template-columns: 1fr;
    }

    .case-metrics {
        grid-template-columns: 1fr;
        gap: var(--space-md);
    }

    .footer-content {
        flex-direction: column;
        gap: var(--space-xl);
    }

    .footer-links {
        flex-wrap: wrap;
    }
}

/* Animations */
@media (prefers-reduced-motion: no-preference) {
    .problem-card,
    .case-card,
    .output-card {
        transition: transform var(--transition-base), box-shadow var(--transition-base);
    }

    .problem-card:hover,
    .case-card:hover {
        transform: translateY(-2px);
        box-shadow: 0 8px 30px rgba(0, 0, 0, 0.08);
    }
}

/* Print Styles */
@media print {
    .header,
    .hero-cta,
    .calculator-inputs input[type="range"] {
        display: none;
    }

    .section {
        padding: var(--space-xl) 0;
        page-break-inside: avoid;
    }
}