/* ============================================
   FACTOURA - factoura-spec.md Section 8
   Substack-inspired: white, borders, minimal chrome
   ============================================ */

/* CSS Variables - Design Tokens (factoura-spec 8.3 Design System) */
:root {
    /* Typography - DESIGN_THEME: Inter (UI), Merriweather (prose), JetBrains Mono (code) */
    --font-serif: 'Merriweather', Georgia, serif;
    --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', Menlo, Monaco, 'Cascadia Code', 'Courier New', monospace;

    /* Font Sizes - Article Typography (prose 65ch, line-height 1.75) */
    --text-article: 21px;
    --text-base: 16px;
    --text-sm: 14px;
    --text-xs: 12px;

    /* Headings - Bold 700, letter-spacing -0.025em for h1/h2 */
    --text-h1: 42px;
    --text-h2: 32px;
    --text-h3: 24px;
    --text-h4: 20px;

    /* Line Heights - Prose 1.75 */
    --leading-article: 1.75;
    --leading-normal: 1.5;
    --leading-tight: 1.3;

    /* Primary (Purple - brand) DESIGN_THEME */
    --primary-50: #f5f3ff;
    --primary-100: #ede9fe;
    --primary-200: #ddd6fe;
    --primary-300: #c4b5fd;
    --primary-400: #a78bfa;
    --primary-500: #5733ed;
    --primary-600: #4c2cd4;
    --primary-700: #4125bb;
    --primary-800: #361fa2;
    --primary-900: #2b1889;

    /* Surface */
    --surface-light: #ffffff;
    --surface-dark: #0f0f1a;

    /* Gray (Neutrals) */
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --gray-950: #0a0a0f;

    /* Light mode - spec 8.3: #333, #666, #999, #E0E0E0, white */
    --color-text: #333333;
    --color-text-light: #666666;
    --color-text-lighter: #999999;
    --color-bg: #ffffff;
    --color-bg-subtle: #ffffff;
    --color-border: #e0e0e0;
    --color-border-light: #e0e0e0;

    /* Accent = Primary (factoura purple) */
    --color-accent: var(--primary-500);
    --color-accent-hover: var(--primary-600);
    --color-link: var(--primary-500);
    --color-link-hover: var(--primary-600);
    --color-success: #0a8754;
    --color-error: #d93025;

    /* Layout - prose max 65ch */
    --max-width-article: 65ch;
    --max-width-wide: 1200px;
    --max-width-narrow: 560px;

    /* Spacing - spec 8.3: section 48px, article 32px, element 16px, container 24px */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    --space-3xl: 64px;
    --spec-section-gap: 48px;
    --spec-article-gap: 32px;
    --spec-container-padding: 24px;

    /* Borders - rounded-lg / rounded-xl (DESIGN_THEME) */
    --border-radius: 8px;
    --border-radius-lg: 12px;
    --border-width: 1px;

    /* Shadows - DESIGN_THEME */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 2px 4px rgba(0, 0, 0, 0.08);
    --shadow-glow: 0 0 20px rgba(87, 51, 237, 0.3);
    --shadow-glow-lg: 0 0 40px rgba(87, 51, 237, 0.4);
    --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.08), 0 4px 12px rgba(0, 0, 0, 0.04);
    --shadow-card-hover: 0 4px 12px rgba(0, 0, 0, 0.1), 0 8px 24px rgba(0, 0, 0, 0.08);

    /* Transition - ease-smooth (DESIGN_THEME) */
    --ease-smooth: cubic-bezier(0.4, 0, 0.2, 1);
    --ease-bounce-in: cubic-bezier(0.68, -0.55, 0.265, 1.55);
    --duration-fast: 200ms;
    --duration-normal: 300ms;
}

/* Dark mode - class-based (DESIGN_THEME) */
.dark,
html.dark {
    --color-text: var(--gray-100);
    --color-text-light: var(--gray-400);
    --color-text-lighter: var(--gray-500);
    --color-bg: var(--surface-dark);
    --color-bg-subtle: var(--gray-900);
    --color-border: var(--gray-800);
    --color-border-light: var(--gray-800);
    --color-link: var(--primary-400);
    --color-link-hover: var(--primary-300);
    --color-accent: var(--primary-500);
    --color-accent-hover: var(--primary-400);
    --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.3), 0 4px 12px rgba(0, 0, 0, 0.2);
    --shadow-card-hover: 0 4px 12px rgba(0, 0, 0, 0.4), 0 8px 24px rgba(0, 0, 0, 0.3);
}

/* ============================================
   BASE STYLES
   ============================================ */

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

html {
    height: 100%;
    overflow-y: auto;
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    margin: 0;
    font-family: var(--font-sans);
    font-size: var(--text-base);
    line-height: var(--leading-normal);
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-y: auto;
    overflow-x: hidden;
    height: 100%;
    display: flex;
    flex-direction: column;
    transition: background-color var(--duration-normal) var(--ease-smooth),
        color var(--duration-normal) var(--ease-smooth);
}

/* Selection - primary tint (DESIGN_THEME) */
::selection {
    background: rgba(87, 51, 237, 0.2);
}

.dark ::selection {
    background: rgba(167, 139, 250, 0.3);
}

/* Focus visible - ring primary (DESIGN_THEME) */
:focus-visible {
    outline: none;
    box-shadow: 0 0 0 2px var(--color-bg), 0 0 0 4px var(--primary-500);
}

.dark :focus-visible {
    box-shadow: 0 0 0 2px var(--gray-900), 0 0 0 4px var(--primary-400);
}

/* ============================================
   TYPOGRAPHY
   ============================================ */

/* Article Content - Beautiful Serif Typography */
.article-content,
.prose {
    font-family: var(--font-serif);
    font-size: var(--text-article);
    line-height: var(--leading-article);
    color: var(--color-text);
}

.article-content p,
.prose p {
    margin-bottom: var(--space-lg);
}

.article-content h1,
.prose h1 {
    font-size: var(--text-h1);
    font-weight: 700;
    line-height: var(--leading-tight);
    letter-spacing: -0.025em;
    margin-bottom: var(--space-lg);
    margin-top: var(--space-2xl);
    color: var(--color-text);
}

.article-content h2,
.prose h2 {
    font-size: var(--text-h2);
    font-weight: 700;
    line-height: var(--leading-tight);
    letter-spacing: -0.025em;
    margin-bottom: var(--space-md);
    margin-top: var(--space-xl);
    color: var(--color-text);
}

.article-content h3,
.prose h3 {
    font-size: var(--text-h3);
    font-weight: 600;
    line-height: var(--leading-tight);
    margin-bottom: var(--space-md);
    margin-top: var(--space-lg);
    color: var(--color-text);
}

.article-content a,
.prose a {
    color: var(--color-link);
    text-decoration: underline;
    text-underline-offset: 2px;
    transition: color var(--duration-fast) var(--ease-smooth);
}

.article-content a:hover,
.prose a:hover {
    color: var(--color-link-hover);
}

.article-content blockquote,
.prose blockquote {
    border-left: 4px solid var(--gray-300);
    padding-left: var(--space-lg);
    margin: var(--space-xl) 0;
    font-style: italic;
    color: var(--color-text-light);
}

.dark .article-content blockquote,
.dark .prose blockquote {
    border-left-color: var(--gray-600);
    color: var(--gray-400);
}

.article-content code,
.prose code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background: var(--gray-100);
    padding: 2px 6px;
    border-radius: var(--border-radius);
}

.dark .article-content code,
.dark .prose code {
    background: var(--gray-800);
    color: var(--gray-200);
}

.article-content pre,
.prose pre {
    background: var(--color-bg-subtle);
    padding: var(--space-md);
    border-radius: var(--border-radius);
    overflow-x: auto;
    margin: var(--space-lg) 0;
}

.article-content ul,
.article-content ol,
.prose ul,
.prose ol {
    margin: var(--space-lg) 0;
    padding-left: var(--space-xl);
}

.article-content li,
.prose li {
    margin-bottom: var(--space-sm);
}

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

/* Links */
a {
    color: var(--color-text);
    text-decoration: none;
    transition: opacity 0.2s;
}

a:hover {
    opacity: 0.7;
}

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

/* ============================================
   LAYOUT UTILITIES
   ============================================ */

.container {
    width: 100%;
    max-width: var(--max-width-wide);
    margin: 0 auto;
    padding: 0 var(--spec-container-padding);
}

.container-article {
    width: 100%;
    max-width: var(--max-width-article);
    margin: 0 auto;
    padding: 0 var(--spec-container-padding);
}

.container-narrow {
    width: 100%;
    max-width: var(--max-width-narrow);
    margin: 0 auto;
    padding: 0 var(--spec-container-padding);
}

/* ============================================
   BUTTONS - MINIMAL STYLE
   ============================================ */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    font-size: var(--text-sm);
    font-weight: 500;
    font-family: var(--font-sans);
    text-align: center;
    border: var(--border-width) solid transparent;
    border-radius: var(--border-radius);
    background: var(--color-bg);
    color: var(--color-text);
    cursor: pointer;
    transition: all var(--duration-fast) var(--ease-smooth);
    text-decoration: none;
    box-shadow: var(--shadow-sm);
}

.btn:focus-visible {
    box-shadow: 0 0 0 2px var(--color-bg), 0 0 0 4px var(--primary-500);
}

/* spec 8.3: subtle hover (color only, no transform) */
.btn:active {
    opacity: 0.9;
}

.btn:hover {
    background: var(--color-bg-subtle);
}

.btn-primary {
    background: var(--primary-500);
    color: white;
    border-color: var(--primary-500);
}

.btn-primary:hover {
    background: var(--primary-600);
    border-color: var(--primary-600);
    color: white;
}

.btn-primary:focus-visible {
    box-shadow: 0 0 0 2px var(--color-bg), 0 0 0 4px var(--primary-500), var(--shadow-glow);
}

.dark .btn-primary:focus-visible {
    box-shadow: 0 0 0 2px var(--gray-900), 0 0 0 4px var(--primary-400);
}

.btn-secondary {
    background: var(--color-bg);
    color: var(--color-text);
    border-color: var(--color-border);
}

.btn-secondary:hover {
    background: var(--color-bg-subtle);
    border-color: var(--gray-300);
}

.dark .btn-secondary {
    background: var(--gray-800);
    color: var(--gray-100);
    border-color: var(--gray-700);
}

.dark .btn-secondary:hover {
    background: var(--gray-700);
    border-color: var(--gray-600);
}

.btn-large {
    padding: 16px 32px;
    font-size: 18px;
}

.btn-small {
    padding: 8px 16px;
    font-size: var(--text-sm);
}

/* Theme toggle (DESIGN_THEME - class-based dark mode) */
.theme-toggle {
    background: none;
    border: none;
    padding: 6px 10px;
    font-size: 18px;
    cursor: pointer;
    border-radius: var(--border-radius);
    transition: background var(--duration-fast) var(--ease-smooth);
}

.theme-toggle:hover {
    background: var(--color-bg-subtle);
}

.theme-toggle:focus-visible {
    outline: none;
    box-shadow: 0 0 0 2px var(--color-bg), 0 0 0 4px var(--primary-500);
}

.hero-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ============================================
   FORMS - CLEAN & SIMPLE
   ============================================ */

input[type="text"],
input[type="email"],
input[type="password"],
input[type="search"],
textarea,
select {
    width: 100%;
    padding: 12px 16px;
    font-size: var(--text-base);
    font-family: var(--font-sans);
    color: var(--color-text);
    background: var(--color-bg);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--border-radius);
    transition: border-color 0.2s;
}

input:focus,
textarea:focus,
select:focus {
    outline: none;
    border-color: var(--primary-500);
    box-shadow: 0 0 0 3px rgba(87, 51, 237, 0.15);
}

.dark input:focus,
.dark textarea:focus,
.dark select:focus {
    border-color: var(--primary-400);
    box-shadow: 0 0 0 3px rgba(167, 139, 250, 0.2);
}

textarea {
    resize: vertical;
    min-height: 120px;
}

label {
    display: block;
    margin-bottom: var(--space-sm);
    font-size: var(--text-sm);
    font-weight: 500;
    color: var(--color-text);
}

/* ============================================
   CARDS - MINIMAL
   ============================================ */

/* Card - spec 8.3: minimal; use for thank-you etc. */
.card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    padding: var(--space-lg);
    overflow: hidden;
    transition: border-color var(--duration-normal) var(--ease-smooth);
}

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

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

.dark .card:hover {
    border-color: var(--gray-600);
}

/* ============================================
   HEADER - SIMPLE & CLEAN
   ============================================ */

.header {
    border-bottom: var(--border-width) solid var(--color-border);
    background: var(--color-bg);
    padding: var(--space-md) 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.header-actions {
    display: flex;
    gap: 24px;
    align-items: center;
}

.header-link {
    font-size: 15px;
    color: var(--color-text);
    font-weight: 500;
}

.header-link:hover {
    color: var(--primary-600);
}

.dark .header-link:hover {
    color: var(--primary-400);
}

.logo {
    font-size: 24px;
    font-weight: 700;
    color: var(--color-text);
    text-decoration: none;
    letter-spacing: -0.5px;
}

.logo:hover {
    opacity: 1;
    color: var(--color-text);
}

/* ============================================
   MAIN CONTENT - spec 8.3 spacing
   ============================================ */

.main-content {
    flex: 1;
    padding: var(--spec-section-gap) 0;
}

.section-label {
    font-size: 14px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: var(--spec-article-gap);
    color: var(--color-text-light);
    font-family: var(--font-sans);
}

/* ============================================
   ARTICLE CARD - spec 8.3: no card shadows, borders only
   ============================================ */

.article-card {
    padding: var(--spec-article-gap) 0;
    border-bottom: 1px solid var(--color-border);
}

.article-card:last-child {
    border-bottom: none;
}

.article-card-link {
    text-decoration: none;
}

.article-card-title {
    font-size: 20px;
    font-weight: 700;
    line-height: 1.3;
    margin-bottom: var(--space-sm);
    color: var(--color-text);
    display: block;
    font-family: var(--font-serif);
}

.article-card-title:hover {
    color: var(--color-link-hover);
}

.article-card-excerpt {
    font-size: 18px;
    line-height: 1.6;
    color: var(--color-text);
    margin-bottom: var(--space-md);
    font-family: var(--font-serif);
}

.article-card-meta {
    font-size: 14px;
    color: var(--color-text-light);
    display: flex;
    align-items: center;
    font-family: var(--font-sans);
}

.meta-dot {
    margin: 0 8px;
}

/* CTA block - spec 8.3: simple border, no gray background */
.cta-block {
    margin-top: var(--spec-section-gap);
    padding: var(--spec-article-gap) 0;
    border-top: 1px solid var(--color-border);
    text-align: center;
}

.cta-block-title {
    margin-bottom: var(--space-md);
    font-size: var(--text-h3);
    font-weight: 700;
    color: var(--color-text);
    font-family: var(--font-serif);
}

.cta-block-text {
    color: var(--color-text-light);
    margin-bottom: var(--space-lg);
    font-size: var(--text-base);
}

/* ============================================
   HERO SECTION
   ============================================ */

.hero-section {
    padding: var(--spec-section-gap) 0;
    border-bottom: 1px solid var(--color-border);
}

.hero-title {
    font-size: 36px;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--space-md);
    color: var(--color-text);
    font-family: var(--font-serif);
}

.hero-subtitle {
    font-size: 18px;
    line-height: 1.6;
    color: var(--color-text-light);
    margin-bottom: var(--space-xl);
    font-family: var(--font-serif);
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
    border-top: 1px solid var(--color-border);
    padding: 40px 0;
    margin-top: auto;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 24px;
}

.footer-links {
    display: flex;
    gap: 32px;
    font-size: 14px;
}

.footer-link {
    color: var(--color-text-light);
}

.footer-link:hover {
    color: var(--color-text);
}

.footer-tagline {
    font-size: 14px;
    color: var(--color-text-lighter);
    margin-top: 8px;
}

.footer-copyright {
    margin-top: 24px;
    padding-top: 24px;
    border-top: 1px solid var(--color-border-light);
    text-align: center;
    font-size: 13px;
    color: var(--color-text-lighter);
}

/* ============================================
   KEYFRAME ANIMATIONS (DESIGN_THEME)
   ============================================ */

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

@keyframes glow {
    0%, 100% { box-shadow: 0 0 20px rgba(87, 51, 237, 0.3); }
    50% { box-shadow: 0 0 30px rgba(87, 51, 237, 0.5); }
}

.animate-fade-in {
    animation: fadeIn 0.3s var(--ease-smooth) forwards;
}

.animate-fade-in-up {
    animation: fadeInUp 0.4s var(--ease-smooth) forwards;
}

.transition-smooth {
    transition: all var(--duration-normal) var(--ease-smooth);
}

/* ============================================
   UTILITIES
   ============================================ */

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

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

.gradient-text {
    background: linear-gradient(to right, var(--primary-500), var(--primary-700));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.dark .gradient-text {
    background: linear-gradient(to right, var(--primary-400), var(--primary-600));
    -webkit-background-clip: text;
    background-clip: text;
}

/* Responsive */
@media (max-width: 768px) {
    :root {
        --text-article: 18px;
        --text-h1: 32px;
        --text-h2: 24px;
        --text-h3: 20px;
    }

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

    .hero-title {
        font-size: 36px;
    }

    .footer-content {
        flex-direction: column;
        align-items: flex-start;
    }

    .footer-links {
        flex-direction: column;
        gap: 16px;
    }
}