/* ============================================================
     MATHEMATICAL CONTINUA - COMPLETE STYLESHEET
     A modern, academic design for mathematical content
     ============================================================ */

/* ============================================================
     1. CSS CUSTOM PROPERTIES (DESIGN TOKENS)
     ============================================================ */
:root {
  /* Color Palette */
  --color-bg-primary: #0d1117;
  --color-bg-secondary: #161b22;
  --color-bg-tertiary: #1c2128;
  --color-bg-card: #21262d;
  --color-bg-elevated: #2d333b;

  --color-accent-primary: #58a6ff;
  --color-accent-secondary: #79c0ff;
  --color-accent-gold: #e3b341;
  --color-accent-green: #3fb950;
  --color-accent-purple: #bc8cff;
  --color-accent-orange: #f78166;
  --color-accent-teal: #39d353;

  --color-text-primary: #e6edf3;
  --color-text-secondary: #8b949e;
  --color-text-muted: #6e7681;
  --color-text-inverse: #0d1117;

  --color-border-default: #30363d;
  --color-border-muted: #21262d;
  --color-border-accent: #388bfd;

  /* Typography */
  --font-sans: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-serif: 'Georgia', 'Times New Roman', serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', 'Consolas', monospace;

  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-md: 1.125rem;
  --font-size-lg: 1.25rem;
  --font-size-xl: 1.5rem;
  --font-size-2xl: 1.875rem;
  --font-size-3xl: 2.25rem;
  --font-size-4xl: 3rem;
  --font-size-5xl: 3.75rem;

  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  --font-weight-extrabold: 800;

  --line-height-tight: 1.25;
  --line-height-snug: 1.375;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.625;
  --line-height-loose: 1.75;
  --line-height-reading: 1.85;

  /* 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;
  --space-32: 8rem;

  /* 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 3px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.5);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.6);
  --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.7);
  --shadow-glow-blue: 0 0 20px rgba(88, 166, 255, 0.15);
  --shadow-glow-gold: 0 0 20px rgba(227, 179, 65, 0.15);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;

  /* Layout */
  --max-width-content: 780px;
  --max-width-wide: 1100px;
  --nav-height: 64px;
}

/* ============================================================
     2. RESET & BASE STYLES
     ============================================================ */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + var(--space-6));
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img,
video {
  max-width: 100%;
  height: auto;
  display: block;
}

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

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

ul,
ol {
  list-style: none;
}

button {
  cursor: pointer;
  border: none;
  background: none;
  font-family: inherit;
}

code {
  font-family: var(--font-mono);
}

sub,
sup {
  font-size: 0.75em;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}

sup {
  top: -0.5em;
}
sub {
  bottom: -0.25em;
}

/* Focus styles for accessibility */
:focus-visible {
  outline: 2px solid var(--color-accent-primary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ============================================================
     3. SITE HEADER & NAVIGATION
     ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(13, 17, 23, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-default);
  height: var(--nav-height);
}

.site-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--max-width-wide);
  margin: 0 auto;
  padding: 0 var(--space-6);
  height: 100%;
  gap: var(--space-6);
}

.site-nav__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-shrink: 0;
  text-decoration: none;
}

.site-nav__logo-mark {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--color-accent-primary), var(--color-accent-purple));
  border-radius: var(--radius-md);
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  color: white;
  flex-shrink: 0;
}

.site-nav__publication-name {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.site-nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  flex-wrap: nowrap;
  overflow: hidden;
}

.site-nav__item {
  flex-shrink: 0;
}

.site-nav__link {
  display: block;
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  transition:
    color var(--transition-fast),
    background-color var(--transition-fast);
  white-space: nowrap;
  text-decoration: none;
}

.site-nav__link:hover {
  color: var(--color-text-primary);
  background-color: var(--color-bg-elevated);
  text-decoration: none;
}

.site-nav__menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
  flex-shrink: 0;
}

.site-nav__menu-toggle:hover {
  background-color: var(--color-bg-elevated);
}

.site-nav__hamburger-bar {
  display: block;
  width: 20px;
  height: 2px;
  background-color: var(--color-text-secondary);
  border-radius: var(--radius-full);
  transition:
    transform var(--transition-base),
    opacity var(--transition-fast);
}

/* ============================================================
     4. HERO SECTION
     ============================================================ */
.hero-section {
  position: relative;
  overflow: hidden;
  padding: var(--space-20) var(--space-6) var(--space-16);
  background: linear-gradient(180deg, var(--color-bg-secondary) 0%, var(--color-bg-primary) 100%);
  border-bottom: 1px solid var(--color-border-default);
}

.hero-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background:
    radial-gradient(ellipse 60% 40% at 70% 20%, rgba(88, 166, 255, 0.06) 0%, transparent 70%),
    radial-gradient(ellipse 40% 60% at 20% 80%, rgba(188, 140, 255, 0.05) 0%, transparent 70%);
  pointer-events: none;
}

.hero-section__inner {
  position: relative;
  z-index: 1;
  max-width: var(--max-width-content);
  margin: 0 auto;
}

.hero-section__category-tag {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-6);
}

.category-tag {
  display: inline-block;
  padding: var(--space-1) var(--space-3);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-accent-primary);
  background-color: rgba(88, 166, 255, 0.1);
  border: 1px solid rgba(88, 166, 255, 0.25);
  border-radius: var(--radius-full);
}

.hero-section__title {
  font-size: clamp(var(--font-size-2xl), 5vw, var(--font-size-4xl));
  font-weight: var(--font-weight-extrabold);
  line-height: var(--line-height-tight);
  color: var(--color-text-primary);
  margin-bottom: var(--space-6);
  letter-spacing: -0.02em;
}

.hero-section__title-emphasis {
  display: block;
  background: linear-gradient(
    135deg,
    var(--color-accent-primary) 0%,
    var(--color-accent-purple) 100%
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-top: var(--space-2);
}

.hero-section__lead {
  font-size: var(--font-size-lg);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-10);
  max-width: 65ch;
}

.hero-section__lead em {
  color: var(--color-accent-secondary);
  font-style: italic;
}

/* Formula Showcase */
.hero-section__formula-showcase {
  margin-bottom: var(--space-10);
}

.formula-showcase__display {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-4);
  padding: var(--space-6) var(--space-8);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-left: 4px solid var(--color-accent-primary);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md), var(--shadow-glow-blue);
  margin-bottom: var(--space-3);
}

.formula-showcase__label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  flex-shrink: 0;
}

.formula-showcase__expression {
  font-family: var(--font-mono);
  font-size: clamp(var(--font-size-lg), 3vw, var(--font-size-2xl));
  font-weight: var(--font-weight-medium);
  color: var(--color-accent-secondary);
  flex: 1;
  text-align: center;
}

.formula-showcase__converges-to {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-accent-gold);
  flex-shrink: 0;
}

.formula-showcase__caption {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  text-align: center;
  font-style: italic;
}

/* Article Metadata */
.article-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-border-default);
}

.article-meta__item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-sm);
}

.article-meta__icon {
  font-size: var(--font-size-base);
}

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

.article-meta__value {
  color: var(--color-text-secondary);
  font-weight: var(--font-weight-medium);
}

/* Background Decoration */
.hero-section__bg-decoration {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 40%;
  pointer-events: none;
  overflow: hidden;
  z-index: 0;
}

.bg-decoration__symbol {
  position: absolute;
  font-family: var(--font-serif);
  font-weight: var(--font-weight-bold);
  color: rgba(88, 166, 255, 0.04);
  user-select: none;
  line-height: 1;
}

.bg-decoration__symbol--pi {
  font-size: 18rem;
  top: -2rem;
  right: -2rem;
  color: rgba(88, 166, 255, 0.05);
}

.bg-decoration__symbol--sin {
  font-size: 5rem;
  bottom: 20%;
  right: 15%;
  color: rgba(188, 140, 255, 0.04);
  font-family: var(--font-mono);
}

.bg-decoration__symbol--sigma {
  font-size: 8rem;
  top: 30%;
  right: 40%;
  color: rgba(227, 179, 65, 0.03);
}

.bg-decoration__symbol--integral {
  font-size: 12rem;
  bottom: -2rem;
  right: 5%;
  color: rgba(63, 185, 80, 0.03);
}

/* ============================================================
     5. TABLE OF CONTENTS
     ============================================================ */
.table-of-contents {
  background-color: var(--color-bg-secondary);
  border-bottom: 1px solid var(--color-border-default);
  padding: var(--space-8) var(--space-6);
}

.table-of-contents__inner {
  max-width: var(--max-width-content);
  margin: 0 auto;
}

.table-of-contents__heading {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-4);
}

.table-of-contents__list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-1);
  counter-reset: toc-counter;
}

.table-of-contents__item {
  counter-increment: toc-counter;
}

.table-of-contents__link {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  transition:
    color var(--transition-fast),
    background-color var(--transition-fast);
  text-decoration: none;
}

.table-of-contents__link::before {
  content: counter(toc-counter, decimal-leading-zero);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-muted);
  font-family: var(--font-mono);
  flex-shrink: 0;
}

.table-of-contents__item .table-of-contents__link::before {
  content: none;
}

.table-of-contents__list > .table-of-contents__item > .table-of-contents__link::before {
  content: counter(toc-counter, decimal-leading-zero);
}

.table-of-contents__link:hover {
  color: var(--color-accent-primary);
  background-color: rgba(88, 166, 255, 0.06);
  text-decoration: none;
}

.table-of-contents__sublist {
  margin-left: var(--space-6);
  margin-top: var(--space-1);
  counter-reset: toc-sub-counter;
}

.table-of-contents__subitem {
  counter-increment: toc-sub-counter;
}

.table-of-contents__subitem .table-of-contents__link {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  padding: var(--space-1) var(--space-3);
}

.table-of-contents__subitem .table-of-contents__link::before {
  content: none;
}

.table-of-contents__subitem .table-of-contents__link:hover {
  color: var(--color-accent-primary);
}

/* ============================================================
     6. MAIN ARTICLE LAYOUT
     ============================================================ */
.article-main {
  max-width: var(--max-width-content);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.article-body {
  padding: var(--space-4) 0;
}

/* ============================================================
     7. ARTICLE SECTIONS
     ============================================================ */
.article-section {
  padding: var(--space-16) 0;
  border-bottom: 1px solid var(--color-border-muted);
}

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

.article-section--alternate {
  /* Subtle visual differentiation for alternating sections */
}

.article-section__inner {
  /* Container for section content */
}

.article-section__heading {
  display: flex;
  align-items: baseline;
  gap: var(--space-4);
  font-size: clamp(var(--font-size-xl), 3vw, var(--font-size-2xl));
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-8);
  letter-spacing: -0.01em;
  line-height: var(--line-height-tight);
}

.article-section__number {
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-accent-primary);
  background-color: rgba(88, 166, 255, 0.1);
  border: 1px solid rgba(88, 166, 255, 0.2);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  flex-shrink: 0;
  letter-spacing: 0.05em;
}

.article-section__content {
  /* Content wrapper */
}

.article-section__paragraph {
  font-size: var(--font-size-md);
  line-height: var(--line-height-reading);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-6);
  max-width: 70ch;
}

.article-section__paragraph--lead {
  font-size: var(--font-size-lg);
  color: var(--color-text-primary);
  font-weight: var(--font-weight-medium);
}

.article-section__paragraph--closing {
  font-style: italic;
  color: var(--color-text-primary);
  font-size: var(--font-size-lg);
  border-left: 3px solid var(--color-accent-primary);
  padding-left: var(--space-5);
  margin-top: var(--space-8);
}

.article-section__paragraph em {
  color: var(--color-accent-secondary);
  font-style: italic;
}

.article-section__paragraph strong {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
}

/* ============================================================
     8. MATH BLOCKS
     ============================================================ */
.math-block {
  margin: var(--space-6) 0;
  padding: var(--space-5) var(--space-6);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-lg);
  overflow-x: auto;
}

.math-block--featured {
  border-left: 4px solid var(--color-accent-primary);
  background: linear-gradient(135deg, rgba(88, 166, 255, 0.05) 0%, var(--color-bg-card) 100%);
  box-shadow: var(--shadow-md), var(--shadow-glow-blue);
  text-align: center;
  padding: var(--space-8);
}

.math-block--result {
  border-left: 4px solid var(--color-accent-green);
  background: linear-gradient(135deg, rgba(63, 185, 80, 0.05) 0%, var(--color-bg-card) 100%);
}

.math-block--inline {
  display: inline-block;
  margin: var(--space-2) 0;
  padding: var(--space-2) var(--space-4);
}

.math-block__expression {
  font-family: var(--font-mono);
  font-size: var(--font-size-base);
  color: var(--color-accent-secondary);
  line-height: var(--line-height-relaxed);
  white-space: pre-wrap;
  word-break: break-word;
}

.math-block--featured .math-block__expression {
  font-size: clamp(var(--font-size-lg), 2.5vw, var(--font-size-xl));
}

/* ============================================================
     9. CONVERGENCE VISUALIZATION
     ============================================================ */
.convergence-visual {
  margin: var(--space-8) 0;
  padding: var(--space-6);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
  overflow: hidden;
}

.convergence-visual__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
}

.convergence-visual__steps {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  overflow-x: auto;
  padding-bottom: var(--space-2);
  flex-wrap: wrap;
}

.convergence-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-5);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-lg);
  min-width: 120px;
  flex-shrink: 0;
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base);
}

.convergence-step:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.convergence-step--seed {
  border-color: rgba(88, 166, 255, 0.3);
}

.convergence-step--iter1 {
  border-color: rgba(188, 140, 255, 0.3);
}

.convergence-step--iter2 {
  border-color: rgba(227, 179, 65, 0.3);
}

.convergence-step--iter3 {
  border-color: rgba(63, 185, 80, 0.3);
}

.convergence-step__label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-text-muted);
}

.convergence-step__digits {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-bold);
  color: var(--color-accent-gold);
}

.convergence-step--seed .convergence-step__digits {
  color: var(--color-accent-primary);
}
.convergence-step--iter1 .convergence-step__digits {
  color: var(--color-accent-purple);
}
.convergence-step--iter2 .convergence-step__digits {
  color: var(--color-accent-gold);
}
.convergence-step--iter3 .convergence-step__digits {
  color: var(--color-accent-green);
}

.convergence-step__value {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  color: var(--color-text-secondary);
  word-break: break-all;
  text-align: center;
}

.convergence-step__arrow {
  font-size: var(--font-size-xl);
  color: var(--color-text-muted);
  flex-shrink: 0;
}

/* ============================================================
     10. DERIVATION BLOCK
     ============================================================ */
.derivation-block {
  margin: var(--space-6) 0;
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
  overflow: hidden;
}

.derivation-block__step {
  padding: var(--space-5) var(--space-6);
  border-bottom: 1px solid var(--color-border-muted);
  background-color: var(--color-bg-secondary);
  transition: background-color var(--transition-fast);
}

.derivation-block__step:last-child {
  border-bottom: none;
}

.derivation-block__step:hover {
  background-color: var(--color-bg-tertiary);
}

.derivation-block__step--result {
  background-color: rgba(63, 185, 80, 0.05);
  border-top: 2px solid var(--color-accent-green);
}

.derivation-block__step-label {
  display: block;
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
}

.derivation-block__step--result .derivation-block__step-label {
  color: var(--color-accent-green);
}

.derivation-block__step .math-block {
  margin: 0;
  background: transparent;
  border: none;
  padding: 0;
}

/* ============================================================
     11. INSIGHT CALLOUTS
     ============================================================ */
.insight-callout {
  display: flex;
  gap: var(--space-4);
  margin: var(--space-8) 0;
  padding: var(--space-5) var(--space-6);
  border-radius: var(--radius-lg);
  border: 1px solid;
}

.insight-callout--mechanism {
  background-color: rgba(88, 166, 255, 0.06);
  border-color: rgba(88, 166, 255, 0.2);
}

.insight-callout--symmetry {
  background-color: rgba(188, 140, 255, 0.06);
  border-color: rgba(188, 140, 255, 0.2);
}

.insight-callout--classification {
  background-color: rgba(227, 179, 65, 0.06);
  border-color: rgba(227, 179, 65, 0.2);
}

.insight-callout--distinction {
  background-color: rgba(247, 129, 102, 0.06);
  border-color: rgba(247, 129, 102, 0.2);
}

.insight-callout--saturation {
  background-color: rgba(63, 185, 80, 0.06);
  border-color: rgba(63, 185, 80, 0.2);
}

.insight-callout__icon {
  font-size: var(--font-size-xl);
  flex-shrink: 0;
  line-height: 1.4;
}

.insight-callout__content {
  flex: 1;
}

.insight-callout__text {
  font-size: var(--font-size-base);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
  margin: 0;
}

.insight-callout__text strong {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
}

.insight-callout__text em {
  font-style: italic;
}

/* ============================================================
     12. TECHNICAL NOTES
     ============================================================ */
.technical-note {
  margin: var(--space-6) 0;
  padding: var(--space-5) var(--space-6);
  background-color: rgba(227, 179, 65, 0.05);
  border: 1px solid rgba(227, 179, 65, 0.2);
  border-left: 4px solid var(--color-accent-gold);
  border-radius: var(--radius-lg);
}

.technical-note--tower {
  background-color: rgba(88, 166, 255, 0.05);
  border-color: rgba(88, 166, 255, 0.2);
  border-left-color: var(--color-accent-primary);
  margin-top: var(--space-6);
}

.technical-note__heading {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-accent-gold);
  margin-bottom: var(--space-3);
}

.technical-note--tower .technical-note__heading {
  color: var(--color-accent-primary);
}

.technical-note__icon {
  font-size: var(--font-size-base);
}

.technical-note__text {
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
}

.technical-note__text em {
  font-style: italic;
}

/* ============================================================
     13. CONDITIONS LIST
     ============================================================ */
.conditions-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin: var(--space-6) 0;
  counter-reset: conditions-counter;
}

.conditions-list__item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-lg);
  transition:
    border-color var(--transition-fast),
    transform var(--transition-base);
}

.conditions-list__item:hover {
  transform: translateX(4px);
}

.conditions-list__item--one {
  border-left: 4px solid var(--color-accent-primary);
}
.conditions-list__item--two {
  border-left: 4px solid var(--color-accent-purple);
}
.conditions-list__item--three {
  border-left: 4px solid var(--color-accent-gold);
}

.conditions-list__number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-bold);
  flex-shrink: 0;
  font-family: var(--font-mono);
}

.conditions-list__item--one .conditions-list__number {
  background-color: rgba(88, 166, 255, 0.15);
  color: var(--color-accent-primary);
}

.conditions-list__item--two .conditions-list__number {
  background-color: rgba(188, 140, 255, 0.15);
  color: var(--color-accent-purple);
}

.conditions-list__item--three .conditions-list__number {
  background-color: rgba(227, 179, 65, 0.15);
  color: var(--color-accent-gold);
}

.conditions-list__content {
  flex: 1;
}

.conditions-list__content .math-block {
  margin: 0 0 var(--space-2);
  padding: var(--space-2) var(--space-3);
  background: transparent;
  border: none;
  border-bottom: 1px solid var(--color-border-muted);
  border-radius: 0;
}

.conditions-list__description {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin: 0;
}

/* ============================================================
     14. VERIFICATION BLOCK
     ============================================================ */
.verification-block {
  margin: var(--space-8) 0;
  padding: var(--space-6);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
}

.verification-block__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
  letter-spacing: 0.03em;
}

.verification-block__checks {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.verification-check {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-bg-card);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border-muted);
}

.verification-check--pass {
  border-color: rgba(63, 185, 80, 0.2);
  background-color: rgba(63, 185, 80, 0.04);
}

.verification-check__icon {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  color: var(--color-accent-green);
  flex-shrink: 0;
  width: 24px;
  text-align: center;
}

.verification-check__formula {
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  color: var(--color-accent-secondary);
  flex: 1;
}

.verification-check__label {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  flex-shrink: 0;
}

/* ============================================================
     15. DESIGN TEMPLATE
     ============================================================ */
.design-template {
  margin: var(--space-8) 0;
  padding: var(--space-6);
  background: linear-gradient(135deg, rgba(188, 140, 255, 0.05) 0%, var(--color-bg-card) 100%);
  border: 1px solid rgba(188, 140, 255, 0.2);
  border-radius: var(--radius-xl);
}

.design-template__heading {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-accent-purple);
  margin-bottom: var(--space-5);
  letter-spacing: 0.02em;
}

.design-template__steps {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin-bottom: var(--space-5);
  counter-reset: template-steps;
  padding-left: 0;
}

.design-template__step {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
  counter-increment: template-steps;
}

.design-template__step::before {
  content: counter(template-steps);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  min-width: 24px;
  background-color: rgba(188, 140, 255, 0.15);
  color: var(--color-accent-purple);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-bold);
  font-family: var(--font-mono);
  margin-top: 1px;
}

.design-template__step em {
  color: var(--color-accent-secondary);
  font-style: italic;
}

.design-template__note {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  font-style: italic;
  line-height: var(--line-height-relaxed);
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border-muted);
}

/* ============================================================
     16. SUBSECTIONS
     ============================================================ */
.subsection-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-10);
  margin-top: var(--space-8);
}

.article-subsection {
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-border-muted);
}

.article-subsection__heading {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-5);
  letter-spacing: -0.01em;
}

/* ============================================================
     17. PRACTICAL EXAMPLE
     ============================================================ */
.practical-example {
  margin: var(--space-6) 0;
  padding: var(--space-6);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
}

.practical-example__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.practical-example__stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}

.practical-example__stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-4);
  background-color: var(--color-bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border-muted);
  text-align: center;
}

.practical-example__stat-value {
  font-family: var(--font-mono);
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  color: var(--color-accent-gold);
}

.practical-example__stat-label {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  text-align: center;
}

.practical-example__note {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  font-style: italic;
  line-height: var(--line-height-relaxed);
}

/* ============================================================
     18. ENGINE TAXONOMY
     ============================================================ */
.engine-taxonomy {
  margin: var(--space-8) 0;
}

.engine-taxonomy__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
}

.engine-taxonomy__grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: var(--space-4);
}

.engine-card {
  display: flex;
  flex-direction: column;
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
  overflow: hidden;
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base);
}

.engine-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.engine-card__header {
  padding: var(--space-4) var(--space-5);
  background-color: var(--color-bg-secondary);
  border-bottom: 1px solid var(--color-border-muted);
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.engine-card__icon {
  font-size: var(--font-size-2xl);
  line-height: 1;
  margin-bottom: var(--space-2);
}

.engine-card--hypergeometric .engine-card__icon {
  color: var(--color-accent-primary);
}
.engine-card--agm .engine-card__icon {
  color: var(--color-accent-purple);
}
.engine-card--newton .engine-card__icon {
  color: var(--color-accent-gold);
}
.engine-card--new .engine-card__icon {
  color: var(--color-accent-green);
}

.engine-card__title {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.engine-card__example {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

.engine-card__badge {
  display: inline-block;
  padding: 2px var(--space-2);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-accent-green);
  background-color: rgba(63, 185, 80, 0.15);
  border: 1px solid rgba(63, 185, 80, 0.3);
  border-radius: var(--radius-full);
  align-self: flex-start;
  margin-top: var(--space-1);
}

.engine-card__body {
  padding: var(--space-4) var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  flex: 1;
}

.engine-card__property {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.engine-card__property-label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--color-text-muted);
}

.engine-card__property-value {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.engine-card--highlighted {
  border-color: rgba(63, 185, 80, 0.3);
  box-shadow:
    0 0 0 1px rgba(63, 185, 80, 0.1),
    var(--shadow-md);
}

.engine-card--highlighted .engine-card__header {
  background: linear-gradient(135deg, rgba(63, 185, 80, 0.08) 0%, var(--color-bg-secondary) 100%);
}

/* ============================================================
     19. COMPARISON NOTE
     ============================================================ */
.comparison-note {
  margin: var(--space-6) 0;
  padding: var(--space-5) var(--space-6);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-lg);
}

.comparison-note__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
}

.comparison-note__text {
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
}

.comparison-note__text em {
  font-style: italic;
  color: var(--color-accent-secondary);
}

.comparison-note__text strong {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
}

/* ============================================================
     20. DEFINITION BLOCK
     ============================================================ */
.definition-block {
  margin: var(--space-8) 0;
  border: 1px solid rgba(88, 166, 255, 0.25);
  border-radius: var(--radius-xl);
  overflow: hidden;
}

.definition-block__term {
  padding: var(--space-3) var(--space-6);
  background: linear-gradient(135deg, rgba(88, 166, 255, 0.12) 0%, rgba(88, 166, 255, 0.06) 100%);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-bold);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-accent-primary);
  border-bottom: 1px solid rgba(88, 166, 255, 0.2);
}

.definition-block__body {
  padding: var(--space-5) var(--space-6);
  background-color: var(--color-bg-card);
}

.definition-block__text {
  font-size: var(--font-size-base);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
  margin: 0;
}

.definition-block__text em {
  font-style: italic;
  color: var(--color-accent-secondary);
}

/* ============================================================
     21. GENERAL TEMPLATE
     ============================================================ */
.general-template {
  margin: var(--space-8) 0;
  padding: var(--space-6);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
}

.general-template__heading {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
}

.general-template__intro {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-4);
}

.general-template .math-block {
  margin-bottom: var(--space-5);
}

.general-template__examples {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.template-example {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-bg-card);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border-muted);
}

.template-example__k {
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-bold);
  min-width: 60px;
}

.template-example--k2 .template-example__k {
  color: var(--color-accent-primary);
}
.template-example--k4 .template-example__k {
  color: var(--color-accent-purple);
}
.template-example--kinf .template-example__k {
  color: var(--color-accent-gold);
}

.template-example__result {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

/* ============================================================
     22. CONTINUA TOWER
     ============================================================ */
.continua-tower {
  margin: var(--space-8) 0;
}

.continua-tower__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-6);
}

.continua-tower__layers {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 0;
}

.tower-layer {
  padding: var(--space-5) var(--space-6);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-lg);
  background-color: var(--color-bg-card);
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base);
  position: relative;
}

.tower-layer:hover {
  transform: translateX(4px);
  box-shadow: var(--shadow-md);
}

.tower-layer--rationals {
  border-left: 4px solid #6e7681;
}
.tower-layer--algebraic {
  border-left: 4px solid var(--color-accent-primary);
}
.tower-layer--analytic {
  border-left: 4px solid var(--color-accent-purple);
  background: linear-gradient(135deg, rgba(188, 140, 255, 0.06) 0%, var(--color-bg-card) 100%);
}
.tower-layer--elliptic {
  border-left: 4px solid var(--color-accent-gold);
}
.tower-layer--periods {
  border-left: 4px solid var(--color-accent-orange);
}
.tower-layer--random {
  border-left: 4px solid var(--color-text-muted);
}

.tower-layer__label {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-2);
}

.tower-layer__symbol {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  font-family: var(--font-serif);
  line-height: 1;
}

.tower-layer--rationals .tower-layer__symbol {
  color: #8b949e;
}
.tower-layer--algebraic .tower-layer__symbol {
  color: var(--color-accent-primary);
}
.tower-layer--analytic .tower-layer__symbol {
  color: var(--color-accent-purple);
}
.tower-layer--elliptic .tower-layer__symbol {
  color: var(--color-accent-gold);
}
.tower-layer--periods .tower-layer__symbol {
  color: var(--color-accent-orange);
}
.tower-layer--random .tower-layer__symbol {
  color: var(--color-text-muted);
}

.tower-layer__name {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.tower-layer__description {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
  margin-bottom: var(--space-2);
}

.tower-layer__mechanism {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-text-muted);
}

.tower-layer__highlight {
  display: inline-block;
  margin-top: var(--space-2);
  padding: var(--space-1) var(--space-3);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  color: var(--color-accent-purple);
  background-color: rgba(188, 140, 255, 0.1);
  border: 1px solid rgba(188, 140, 255, 0.25);
  border-radius: var(--radius-full);
}

.tower-layer__connector {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 32px;
  font-size: var(--font-size-xl);
  color: var(--color-text-muted);
  font-weight: var(--font-weight-bold);
}

/* ============================================================
     23. MINIMAL EXPANSION
     ============================================================ */
.minimal-expansion {
  margin: var(--space-8) 0;
  padding: var(--space-6);
  background: linear-gradient(135deg, rgba(63, 185, 80, 0.05) 0%, var(--color-bg-card) 100%);
  border: 1px solid rgba(63, 185, 80, 0.2);
  border-radius: var(--radius-xl);
}

.minimal-expansion__heading {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-accent-green);
  margin-bottom: var(--space-4);
}

.minimal-expansion__text {
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-5);
}

.minimal-expansion__properties {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: var(--space-3);
}

.expansion-property {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
}

.expansion-property--not {
  background-color: rgba(247, 129, 102, 0.06);
  border: 1px solid rgba(247, 129, 102, 0.15);
  color: var(--color-text-secondary);
}

.expansion-property--is {
  background-color: rgba(63, 185, 80, 0.06);
  border: 1px solid rgba(63, 185, 80, 0.15);
  color: var(--color-text-secondary);
}

.expansion-property__icon {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-bold);
  flex-shrink: 0;
}

.expansion-property--not .expansion-property__icon {
  color: var(--color-accent-orange);
}
.expansion-property--is .expansion-property__icon {
  color: var(--color-accent-green);
}

/* ============================================================
     24. RESEARCH QUESTION
     ============================================================ */
.research-question {
  margin: var(--space-8) 0;
  padding: var(--space-6);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
}

.research-question__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-4);
}

.research-question__text {
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-5);
}

.research-question__text strong {
  color: var(--color-text-primary);
}

.research-question__constants {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.constant-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-5);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-lg);
  min-width: 80px;
  transition: transform var(--transition-base);
}

.constant-card:hover {
  transform: translateY(-2px);
}

.constant-card__symbol {
  font-family: var(--font-serif);
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  line-height: 1;
}

.constant-card--pi .constant-card__symbol {
  color: var(--color-accent-primary);
}
.constant-card--e .constant-card__symbol {
  color: var(--color-accent-purple);
}
.constant-card--zeta .constant-card__symbol {
  color: var(--color-accent-gold);
}
.constant-card--gamma .constant-card__symbol {
  color: var(--color-accent-orange);
}

.constant-card__status {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  padding: 2px var(--space-2);
  border-radius: var(--radius-full);
}

.constant-card__status--known {
  color: var(--color-accent-green);
  background-color: rgba(63, 185, 80, 0.12);
  border: 1px solid rgba(63, 185, 80, 0.25);
}

.constant-card__status--open {
  color: var(--color-accent-gold);
  background-color: rgba(227, 179, 65, 0.12);
  border: 1px solid rgba(227, 179, 65, 0.25);
}

/* ============================================================
     25. KEY DEMONSTRATIONS
     ============================================================ */
.key-demonstrations {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  margin: var(--space-8) 0;
}

.demonstration {
  display: flex;
  gap: var(--space-5);
  padding: var(--space-6);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-xl);
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base);
}

.demonstration:hover {
  transform: translateX(4px);
  box-shadow: var(--shadow-md);
}

.demonstration--one {
  border-left: 4px solid var(--color-accent-primary);
}
.demonstration--two {
  border-left: 4px solid var(--color-accent-purple);
}
.demonstration--three {
  border-left: 4px solid var(--color-accent-gold);
}

.demonstration__number {
  font-family: var(--font-serif);
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-bold);
  line-height: 1;
  flex-shrink: 0;
  width: 48px;
  text-align: center;
  opacity: 0.3;
}

.demonstration--one .demonstration__number {
  color: var(--color-accent-primary);
}
.demonstration--two .demonstration__number {
  color: var(--color-accent-purple);
}
.demonstration--three .demonstration__number {
  color: var(--color-accent-gold);
}

.demonstration__content {
  flex: 1;
}

.demonstration__heading {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
}

.demonstration__text {
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
  color: var(--color-text-secondary);
  margin: 0;
}

/* ============================================================
     26. CLOSING PRINCIPLE
     ============================================================ */
.closing-principle {
  position: relative;
  margin: var(--space-10) 0;
  padding: var(--space-8) var(--space-10);
  background: linear-gradient(135deg, rgba(88, 166, 255, 0.06) 0%, rgba(188, 140, 255, 0.06) 100%);
  border: 1px solid rgba(88, 166, 255, 0.2);
  border-radius: var(--radius-2xl);
  text-align: center;
}

.closing-principle__ornament {
  font-size: var(--font-size-4xl);
  color: rgba(88, 166, 255, 0.2);
  line-height: 1;
  font-family: var(--font-serif);
  display: block;
  margin-bottom: var(--space-4);
}

.closing-principle__ornament--close {
  margin-bottom: 0;
  margin-top: var(--space-4);
}

.closing-principle__text {
  font-size: clamp(var(--font-size-base), 2vw, var(--font-size-lg));
  line-height: var(--line-height-relaxed);
  color: var(--color-text-primary);
  font-style: italic;
  max-width: 60ch;
  margin: 0 auto;
}

/* ============================================================
     27. ARTICLE FOOTER
     ============================================================ */
.article-footer {
  background-color: var(--color-bg-secondary);
  border-top: 1px solid var(--color-border-default);
  margin-top: var(--space-16);
}

.article-footer__inner {
  max-width: var(--max-width-wide);
  margin: 0 auto;
  padding: var(--space-16) var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-12);
}

/* Key Concepts */
.key-concepts__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
}

.key-concepts__grid {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.concept-tag {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-full);
  transition:
    color var(--transition-fast),
    border-color var(--transition-fast),
    background-color var(--transition-fast);
  cursor: default;
}

.concept-tag:hover {
  color: var(--color-accent-primary);
  border-color: rgba(88, 166, 255, 0.3);
  background-color: rgba(88, 166, 255, 0.06);
}

/* References */
.references-section__heading {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
}

.references-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.references-list__item {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: baseline;
  padding: var(--space-4) var(--space-5);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-muted);
  border-radius: var(--radius-lg);
  transition: border-color var(--transition-fast);
}

.references-list__item:hover {
  border-color: var(--color-border-default);
}

.references-list__authors {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.references-list__title {
  font-size: var(--font-size-sm);
  font-style: italic;
  color: var(--color-accent-secondary);
}

.references-list__context {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* Site Footer */
.site-footer {
  padding-top: var(--space-8);
  border-top: 1px solid var(--color-border-default);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-4);
  text-align: center;
}

.site-footer__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.site-footer__logo-mark {
  font-size: var(--font-size-xl);
  color: var(--color-accent-primary);
}

.site-footer__name {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.site-footer__tagline {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  max-width: 50ch;
  line-height: var(--line-height-relaxed);
}

.site-footer__nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-2);
}

.site-footer__link {
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  border-radius: var(--radius-md);
  transition:
    color var(--transition-fast),
    background-color var(--transition-fast);
  text-decoration: none;
}

.site-footer__link:hover {
  color: var(--color-accent-primary);
  background-color: rgba(88, 166, 255, 0.06);
  text-decoration: none;
}

.site-footer__copyright {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

/* ============================================================
     28. SCROLLBAR STYLING
     ============================================================ */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--color-bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--color-bg-elevated);
  border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--color-text-muted);
}

/* ============================================================
     29. SELECTION STYLING
     ============================================================ */
::selection {
  background-color: rgba(88, 166, 255, 0.25);
  color: var(--color-text-primary);
}

/* ============================================================
     30. RESPONSIVE DESIGN - TABLET (max-width: 900px)
     ============================================================ */
@media (max-width: 900px) {
  :root {
    --nav-height: 56px;
  }

  .site-nav__links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    flex-direction: column;
    background-color: var(--color-bg-secondary);
    border-bottom: 1px solid var(--color-border-default);
    padding: var(--space-4);
    gap: var(--space-1);
    z-index: 99;
  }

  .site-nav__links.is-open {
    display: flex;
  }

  .site-nav__link {
    padding: var(--space-3) var(--space-4);
    font-size: var(--font-size-base);
  }

  .site-nav__menu-toggle {
    display: flex;
  }

  .hero-section {
    padding: var(--space-12) var(--space-5) var(--space-10);
  }

  .hero-section__bg-decoration {
    opacity: 0.5;
  }

  .formula-showcase__display {
    flex-direction: column;
    text-align: center;
    padding: var(--space-5);
  }

  .article-meta {
    flex-direction: column;
    gap: var(--space-3);
  }

  .table-of-contents__list {
    grid-template-columns: 1fr;
  }

  .engine-taxonomy__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .practical-example__stats {
    grid-template-columns: repeat(3, 1fr);
  }

  .convergence-visual__steps {
    flex-direction: column;
    align-items: stretch;
  }

  .convergence-step__arrow {
    transform: rotate(90deg);
    align-self: center;
  }

  .closing-principle {
    padding: var(--space-6) var(--space-6);
  }
}

/* ============================================================
     31. RESPONSIVE DESIGN - MOBILE (max-width: 600px)
     ============================================================ */
@media (max-width: 600px) {
  .hero-section {
    padding: var(--space-10) var(--space-4) var(--space-8);
  }

  .hero-section__bg-decoration {
    display: none;
  }

  .article-main {
    padding: 0 var(--space-4);
  }

  .article-section {
    padding: var(--space-10) 0;
  }

  .article-section__heading {
    flex-direction: column;
    gap: var(--space-2);
  }

  .engine-taxonomy__grid {
    grid-template-columns: 1fr;
  }

  .practical-example__stats {
    grid-template-columns: 1fr;
  }

  .demonstration {
    flex-direction: column;
    gap: var(--space-3);
  }

  .demonstration__number {
    font-size: var(--font-size-2xl);
    width: auto;
    text-align: left;
  }

  .minimal-expansion__properties {
    grid-template-columns: 1fr;
  }

  .research-question__constants {
    justify-content: center;
  }

  .formula-showcase__expression {
    font-size: var(--font-size-base);
  }

  .table-of-contents {
    padding: var(--space-6) var(--space-4);
  }

  .article-footer__inner {
    padding: var(--space-10) var(--space-4);
  }

  .closing-principle {
    padding: var(--space-6) var(--space-4);
  }

  .closing-principle__ornament {
    font-size: var(--font-size-3xl);
  }

  .verification-block__checks {
    gap: var(--space-2);
  }

  .verification-check {
    flex-wrap: wrap;
  }

  .verification-check__label {
    width: 100%;
    margin-left: calc(24px + var(--space-4));
  }

  .conditions-list__item {
    flex-direction: column;
    gap: var(--space-3);
  }

  .tower-layer {
    padding: var(--space-4);
  }
}

/* ============================================================
     32. PRINT STYLES
     ============================================================ */
@media print {
  .site-header,
  .site-nav__menu-toggle,
  .hero-section__bg-decoration,
  .table-of-contents {
    display: none;
  }

  body {
    background: white;
    color: black;
  }

  .article-main {
    max-width: 100%;
    padding: 0;
  }

  .math-block {
    border: 1px solid #ccc;
    background: #f9f9f9;
  }

  .math-block__expression {
    color: #333;
  }

  a {
    color: #333;
    text-decoration: underline;
  }
}

/* ============================================================
     33. ANIMATION & REDUCED MOTION
     ============================================================ */
@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;
  }
}

/* Subtle entrance animations for supported users */
@media (prefers-reduced-motion: no-preference) {
  .article-section {
    animation: fadeInUp 0.4s ease both;
  }

  @keyframes fadeInUp {
    from {
      opacity: 0;
      transform: translateY(12px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }

  .engine-card {
    animation: fadeIn 0.3s ease both;
  }

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