/* ==========================================================================
   AI Fairness Observatory - Main Stylesheet
   Design Philosophy: Academic rigor meets public accessibility
   ========================================================================== */

/* --------------------------------------------------------------------------
   Design Tokens
   -------------------------------------------------------------------------- */
:root {
    /* Color Palette - Professional, trustworthy, academic */
    --color-primary: #1e3a5f;        /* Deep navy - trust, authority */
    --color-primary-light: #2d5a8a;
    --color-primary-dark: #0f1f33;
    
    --color-accent: #3b82f6;         /* Bright blue - clarity, action */
    --color-accent-light: #60a5fa;
    --color-accent-dark: #1d4ed8;
    
    --color-warning: #f59e0b;        /* Amber - attention, caution */
    --color-warning-light: #fbbf24;
    
    --color-success: #10b981;        /* Green - positive, verified */
    --color-danger: #ef4444;         /* Red - critical, alert */
    
    /* Neutral palette */
    --color-background: #0a0f14;
    --color-background-alt: #111820;
    --color-surface: #1a2332;
    --color-surface-elevated: #222d3d;
    
    --color-text: #e8edf3;
    --color-text-secondary: #94a3b8;
    --color-text-muted: #64748b;
    
    --color-border: #2d3b4d;
    --color-border-light: #3d4d5f;
    
    /* Glass effect */
    --glass-bg: rgba(26, 35, 50, 0.7);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --glass-blur: 12px;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent-dark) 100%);
    --gradient-accent: linear-gradient(135deg, var(--color-accent) 0%, var(--color-accent-light) 100%);
    --gradient-text: linear-gradient(135deg, var(--color-accent-light) 0%, var(--color-accent) 100%);
    
    /* Typography */
    --font-sans: 'IBM Plex Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-serif: 'Merriweather', Georgia, serif;
    --font-mono: 'IBM Plex Mono', 'Consolas', monospace;
    
    /* Font sizes */
    --text-xs: 0.75rem;
    --text-sm: 0.875rem;
    --text-base: 1rem;
    --text-lg: 1.125rem;
    --text-xl: 1.25rem;
    --text-2xl: 1.5rem;
    --text-3xl: 1.875rem;
    --text-4xl: 2.25rem;
    --text-5xl: 3rem;
    --text-6xl: 3.75rem;
    
    /* Line heights */
    --leading-tight: 1.25;
    --leading-normal: 1.5;
    --leading-relaxed: 1.75;
    
    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;
    --space-20: 5rem;
    --space-24: 6rem;
    
    /* Border radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-2xl: 24px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.25);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.35);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;
    --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
    
    /* Layout */
    --container-max: 1200px;
    --container-narrow: 800px;
}

/* --------------------------------------------------------------------------
   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: var(--text-base);
    line-height: var(--leading-normal);
    color: var(--color-text);
    background: var(--color-background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* --------------------------------------------------------------------------
   Typography
   -------------------------------------------------------------------------- */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-sans);
    font-weight: 600;
    line-height: var(--leading-tight);
    color: var(--color-text);
}

h1 {
    font-size: var(--text-5xl);
    font-weight: 700;
    letter-spacing: -0.02em;
}

h2 {
    font-size: var(--text-3xl);
    margin-bottom: var(--space-6);
}

h3 {
    font-size: var(--text-xl);
    margin-bottom: var(--space-4);
}

h4 {
    font-size: var(--text-lg);
    margin-bottom: var(--space-3);
}

p {
    margin-bottom: var(--space-4);
    color: var(--color-text-secondary);
}

.lead {
    font-size: var(--text-xl);
    color: var(--color-text-secondary);
    line-height: var(--leading-relaxed);
}

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

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

strong {
    font-weight: 600;
    color: var(--color-text);
}

em {
    font-style: italic;
}

code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background: var(--color-surface);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
}

.text-gradient {
    background: var(--gradient-text);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* --------------------------------------------------------------------------
   Layout
   -------------------------------------------------------------------------- */
.container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--space-6);
}

.section {
    padding: var(--space-20) 0;
}

.article-content {
    max-width: var(--container-narrow);
    margin: 0 auto;
}

.article-content h2 {
    margin-top: var(--space-12);
}

.article-content h3 {
    margin-top: var(--space-8);
}

.article-content ul, .article-content ol {
    margin-bottom: var(--space-6);
    padding-left: var(--space-6);
}

.article-content li {
    margin-bottom: var(--space-2);
    color: var(--color-text-secondary);
}

/* --------------------------------------------------------------------------
   Header
   -------------------------------------------------------------------------- */
.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(10, 15, 20, 0.9);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-border);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.site-logo {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    color: var(--color-text);
    text-decoration: none;
}

.logo-icon {
    font-size: var(--text-2xl);
}

.logo-text {
    font-size: var(--text-lg);
    font-weight: 600;
}

.main-nav ul {
    display: flex;
    list-style: none;
    gap: var(--space-8);
}

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

.main-nav a:hover,
.main-nav a.active {
    color: var(--color-accent);
}

/* Mobile menu */
.mobile-menu-checkbox {
    display: none;
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 44px;
    height: 44px;
    cursor: pointer;
    z-index: 101;
}

.mobile-menu-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    margin: 3px 0;
    transition: var(--transition-base);
}

/* --------------------------------------------------------------------------
   Hero Section
   -------------------------------------------------------------------------- */
.hero {
    padding: var(--space-24) 0;
    background: var(--color-background-alt);
    border-bottom: 1px solid var(--color-border);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 70%;
    height: 200%;
    background: radial-gradient(ellipse, rgba(59, 130, 246, 0.08) 0%, transparent 70%);
    pointer-events: none;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-16);
    align-items: center;
}

.hero-tagline {
    font-size: var(--text-sm);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-accent);
    margin-bottom: var(--space-4);
}

.hero h1 {
    margin-bottom: var(--space-6);
}

.hero-lead {
    font-size: var(--text-lg);
    color: var(--color-text-secondary);
    margin-bottom: var(--space-8);
    max-width: 540px;
}

.hero-cta {
    display: flex;
    gap: var(--space-4);
    flex-wrap: wrap;
}

/* Hero visual */
.hero-visual {
    position: relative;
}

.bias-illustration {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--space-8);
}

.patient-card {
    background: var(--color-surface-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-5);
    margin-bottom: var(--space-4);
}

.patient-name {
    font-weight: 600;
    font-size: var(--text-lg);
    margin-bottom: var(--space-2);
}

.patient-symptoms {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
    margin-bottom: var(--space-3);
}

.patient-result {
    font-size: var(--text-sm);
    font-weight: 500;
    padding: var(--space-2) var(--space-3);
    border-radius: var(--radius-sm);
    display: inline-block;
}

.result-urgent {
    background: rgba(239, 68, 68, 0.15);
    color: #f87171;
    border: 1px solid rgba(239, 68, 68, 0.3);
}

.result-routine {
    background: rgba(245, 158, 11, 0.15);
    color: #fbbf24;
    border: 1px solid rgba(245, 158, 11, 0.3);
}

.vs-indicator {
    text-align: center;
    font-size: var(--text-lg);
    color: var(--color-text-muted);
    margin: var(--space-3) 0;
}

.illustration-caption {
    text-align: center;
    font-size: var(--text-sm);
    color: var(--color-text-muted);
    font-style: italic;
    margin-top: var(--space-4);
}

/* --------------------------------------------------------------------------
   Page Header
   -------------------------------------------------------------------------- */
.page-header {
    background: var(--color-background-alt);
    padding: var(--space-16) 0;
    border-bottom: 1px solid var(--color-border);
}

.breadcrumb {
    font-size: var(--text-sm);
    color: var(--color-text-muted);
    margin-bottom: var(--space-4);
}

.breadcrumb a {
    color: var(--color-text-muted);
}

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

.breadcrumb span {
    margin: 0 var(--space-2);
}

.page-header h1 {
    margin-bottom: var(--space-4);
}

.page-header .lead {
    max-width: 600px;
}

/* --------------------------------------------------------------------------
   Buttons
   -------------------------------------------------------------------------- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-3) var(--space-6);
    font-family: var(--font-sans);
    font-size: var(--text-sm);
    font-weight: 600;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    text-decoration: none;
    transition: all var(--transition-base) var(--ease-spring);
}

.btn-primary {
    background: var(--gradient-accent);
    color: white;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.4);
    color: white;
}

.btn-secondary {
    background: var(--color-surface);
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background: var(--color-surface-elevated);
    border-color: var(--color-accent);
    transform: translateY(-2px);
    color: var(--color-text);
}

.btn-outline {
    background: transparent;
    color: var(--color-accent);
    border: 2px solid var(--color-accent);
}

.btn-outline:hover {
    background: var(--color-accent);
    color: white;
    transform: translateY(-2px);
}

/* --------------------------------------------------------------------------
   Glass Cards
   -------------------------------------------------------------------------- */
.glass-card {
    background: var(--glass-bg);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-xl);
    box-shadow: var(--glass-shadow);
    padding: var(--space-8);
    transition: all var(--transition-base) var(--ease-spring);
}

.glass-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.4);
}

/* --------------------------------------------------------------------------
   Stats Grid
   -------------------------------------------------------------------------- */
.stat-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-6);
    margin: var(--space-12) 0;
}

.stat-card {
    text-align: center;
    padding: var(--space-8);
}

.stat-number {
    font-size: var(--text-5xl);
    font-weight: 700;
    background: var(--gradient-text);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-2);
}

.stat-label {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
}

/* --------------------------------------------------------------------------
   Approach Grid
   -------------------------------------------------------------------------- */
.approach-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-6);
    margin-top: var(--space-10);
}

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

.approach-icon {
    font-size: var(--text-4xl);
    margin-bottom: var(--space-4);
}

.approach-card h3 {
    font-size: var(--text-lg);
}

.approach-card p {
    font-size: var(--text-sm);
}

/* --------------------------------------------------------------------------
   Timeline
   -------------------------------------------------------------------------- */
.status-timeline {
    max-width: 600px;
    margin: var(--space-10) auto 0;
}

.timeline-item {
    display: flex;
    gap: var(--space-6);
    padding-bottom: var(--space-8);
    position: relative;
}

.timeline-item:not(:last-child)::before {
    content: '';
    position: absolute;
    left: 11px;
    top: 28px;
    bottom: 0;
    width: 2px;
    background: var(--color-border);
}

.timeline-marker {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--color-surface);
    border: 2px solid var(--color-border);
    flex-shrink: 0;
}

.timeline-item.completed .timeline-marker {
    background: var(--color-success);
    border-color: var(--color-success);
}

.timeline-item.active .timeline-marker {
    background: var(--color-accent);
    border-color: var(--color-accent);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.3);
}

.timeline-content h4 {
    margin-bottom: var(--space-1);
}

.timeline-content p {
    font-size: var(--text-sm);
    margin-bottom: 0;
}

/* --------------------------------------------------------------------------
   Evidence Callout
   -------------------------------------------------------------------------- */
.evidence-callout {
    margin: var(--space-10) 0;
}

.evidence-callout h3 {
    margin-bottom: var(--space-4);
}

.evidence-list {
    list-style: none;
    padding: 0;
    margin-bottom: var(--space-6);
}

.evidence-list li {
    padding: var(--space-3) 0;
    border-bottom: 1px solid var(--color-border);
}

.evidence-list li:last-child {
    border-bottom: none;
}

.callout-conclusion {
    font-size: var(--text-lg);
    font-weight: 500;
    color: var(--color-text);
    font-style: italic;
}

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

.cta-content {
    text-align: center;
    max-width: 700px;
    margin: 0 auto;
}

.cta-content h2 {
    margin-bottom: var(--space-4);
}

.cta-buttons {
    display: flex;
    justify-content: center;
    gap: var(--space-4);
    margin-top: var(--space-8);
    flex-wrap: wrap;
}

.cta-box {
    margin-top: var(--space-12);
    text-align: center;
}

.cta-box h3 {
    margin-bottom: var(--space-2);
}

.cta-box p {
    margin-bottom: var(--space-6);
}

.cta-box .cta-buttons {
    margin-top: var(--space-4);
}

/* --------------------------------------------------------------------------
   Section Headers
   -------------------------------------------------------------------------- */
.section-header {
    text-align: center;
    margin-bottom: var(--space-12);
}

.section-lead {
    font-size: var(--text-lg);
    color: var(--color-text-secondary);
    max-width: 600px;
    margin: var(--space-4) auto 0;
}

/* --------------------------------------------------------------------------
   Footer
   -------------------------------------------------------------------------- */
.site-footer {
    background: var(--color-surface);
    padding: var(--space-16) 0 var(--space-8);
    border-top: 1px solid var(--color-border);
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: var(--space-16);
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    margin-bottom: var(--space-4);
}

.footer-mission {
    color: var(--color-text-secondary);
    max-width: 400px;
}

.footer-nav {
    display: flex;
    gap: var(--space-12);
}

.footer-col h4 {
    font-size: var(--text-sm);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-muted);
    margin-bottom: var(--space-4);
}

.footer-col ul {
    list-style: none;
}

.footer-col li {
    margin-bottom: var(--space-2);
}

.footer-col a {
    color: var(--color-text-secondary);
    font-size: var(--text-sm);
}

.footer-col a:hover {
    color: var(--color-accent);
}

.footer-bottom {
    margin-top: var(--space-12);
    padding-top: var(--space-6);
    border-top: 1px solid var(--color-border);
    text-align: center;
}

.footer-bottom p {
    font-size: var(--text-sm);
    color: var(--color-text-muted);
}

/* --------------------------------------------------------------------------
   Responsive Design
   -------------------------------------------------------------------------- */
@media (max-width: 1024px) {
    .hero .container {
        grid-template-columns: 1fr;
        gap: var(--space-12);
    }
    
    .hero-visual {
        max-width: 500px;
        margin: 0 auto;
    }
    
    .stat-grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .approach-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    :root {
        --text-5xl: 2.25rem;
        --text-4xl: 1.875rem;
        --text-3xl: 1.5rem;
    }
    
    .mobile-menu-toggle {
        display: flex;
    }
    
    .main-nav {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        background: var(--color-background);
        border-bottom: 1px solid var(--color-border);
        padding: var(--space-6);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: var(--transition-base);
    }
    
    .mobile-menu-checkbox:checked ~ .main-nav {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .main-nav ul {
        flex-direction: column;
        gap: var(--space-4);
    }
    
    .mobile-menu-checkbox:checked ~ .mobile-menu-toggle span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    
    .mobile-menu-checkbox:checked ~ .mobile-menu-toggle span:nth-child(2) {
        opacity: 0;
    }
    
    .mobile-menu-checkbox:checked ~ .mobile-menu-toggle span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }
    
    .stat-grid {
        grid-template-columns: 1fr;
    }
    
    .approach-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        gap: var(--space-10);
    }
    
    .footer-nav {
        flex-direction: column;
        gap: var(--space-8);
    }
    
    .hero {
        padding: var(--space-16) 0;
    }
    
    .page-header {
        padding: var(--space-10) 0;
    }
    
    .section {
        padding: var(--space-12) 0;
    }
    
    .glass-card {
        padding: var(--space-6);
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--space-4);
    }
    
    .hero-cta {
        flex-direction: column;
    }
    
    .hero-cta .btn {
        width: 100%;
    }
    
    .cta-buttons {
        flex-direction: column;
    }
    
    .cta-buttons .btn {
        width: 100%;
    }
}

/* --------------------------------------------------------------------------
   Accessibility
   -------------------------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

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

/* Skip link for keyboard users */
.skip-link {
    position: absolute;
    top: -100%;
    left: 50%;
    transform: translateX(-50%);
    padding: var(--space-3) var(--space-6);
    background: var(--color-accent);
    color: white;
    text-decoration: none;
    font-weight: 600;
    border-radius: var(--radius-md);
    z-index: 1000;
    transition: top var(--transition-fast);
}

.skip-link:focus {
    top: var(--space-4);
}

/* Enhanced focus states */
a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
    outline: 3px solid var(--color-accent);
    outline-offset: 3px;
}

/* Ensure interactive elements have visible focus */
.btn:focus-visible {
    outline: 3px solid white;
    outline-offset: 3px;
    box-shadow: 0 0 0 6px var(--color-accent);
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --color-border: #ffffff;
        --glass-border: rgba(255, 255, 255, 0.3);
    }
    
    .btn-primary {
        border: 2px solid white;
    }
}