/* ============================================================
           THE EXTENSION LADDER — STYLESHEET
           A mathematical essay on how number systems grow
           ============================================================ */

/* ============================================================
           1. CSS CUSTOM PROPERTIES (DESIGN TOKENS)
           ============================================================ */

:root {
  /* Color Palette */
  --color-bg: #0f1117;
  --color-bg-alt: #161b27;
  --color-bg-card: #1a2035;
  --color-bg-card-hover: #1f2640;
  --color-surface: #212840;
  --color-surface-alt: #252d4a;
  --color-border: #2e3a5c;
  --color-border-light: #3a4a70;

  /* Text */
  --color-text-primary: #e8eaf6;
  --color-text-secondary: #9ba8c8;
  --color-text-muted: #6b7a9e;
  --color-text-accent: #a5b4fc;

  /* Accent Colors — one per ladder level */
  --color-integer: #60a5fa; /* Level 0 — blue */
  --color-rational: #34d399; /* Level 1 — emerald */
  --color-algebraic: #f59e0b; /* Level 2 — amber */
  --color-real: #f87171; /* Level 3 — rose */
  --color-complex: #c084fc; /* Level 4 — violet */

  /* Brand / Primary */
  --color-primary: #818cf8;
  --color-primary-light: #a5b4fc;
  --color-primary-dark: #6366f1;
  --color-highlight: #312e81;

  /* Semantic */
  --color-success: #34d399;
  --color-warning: #fbbf24;
  --color-info: #60a5fa;

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

  /* Type Scale */
  --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;

  /* 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;

  /* Layout */
  --max-width-content: 72ch;
  --max-width-wide: 90rem;
  --max-width-article: 80rem;

  /* Borders */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.5);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.6);
  --shadow-glow: 0 0 24px rgba(129, 140, 248, 0.15);

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

  /* Z-index layers */
  --z-base: 0;
  --z-raised: 10;
  --z-nav: 100;
  --z-overlay: 200;
  --z-top: 300;
}

/* ============================================================
           2. RESET & BASE
           ============================================================ */

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-text-primary);
  background-color: var(--color-bg);
  min-height: 100vh;
  overflow-x: hidden;
}

/* Subtle grid background texture */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(129, 140, 248, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(129, 140, 248, 0.03) 1px, transparent 1px);
  background-size: 48px 48px;
  pointer-events: none;
  z-index: var(--z-base);
}

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

a {
  color: var(--color-primary-light);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: color var(--transition-fast);
}

a:hover {
  color: #fff;
}

ul,
ol {
  list-style: none;
}

em {
  font-style: italic;
  color: var(--color-text-accent);
}

strong {
  font-weight: 700;
  color: var(--color-text-primary);
}

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

/* Selection */
::selection {
  background: rgba(129, 140, 248, 0.3);
  color: #fff;
}

/* ============================================================
           3. TYPOGRAPHY UTILITIES
           ============================================================ */

.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;
}

/* ============================================================
           4. SITE HEADER & NAVIGATION
           ============================================================ */

.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-nav);
  background: rgba(15, 17, 23, 0.85);
  backdrop-filter: blur(16px) saturate(1.4);
  -webkit-backdrop-filter: blur(16px) saturate(1.4);
  border-bottom: 1px solid var(--color-border);
}

.site-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
  max-width: var(--max-width-wide);
  margin: 0 auto;
  padding: var(--space-4) var(--space-6);
}

/* Brand */
.nav-brand {
  flex-shrink: 0;
}

.nav-brand-label {
  font-family: var(--font-serif);
  font-size: var(--text-sm);
  font-weight: 400;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  white-space: nowrap;
}

/* Nav menu */
.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  flex-wrap: wrap;
}

.nav-item {
  display: flex;
}

.nav-link {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  text-decoration: none;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  transition:
    color var(--transition-fast),
    background var(--transition-fast);
  white-space: nowrap;
}

.nav-link:hover {
  color: var(--color-text-primary);
  background: rgba(129, 140, 248, 0.1);
}

/* Hamburger toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
  width: 40px;
  height: 40px;
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  flex-shrink: 0;
  transition:
    border-color var(--transition-fast),
    background var(--transition-fast);
}

.nav-toggle:hover {
  background: rgba(129, 140, 248, 0.1);
  border-color: var(--color-primary);
}

.nav-toggle-bar {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--color-text-secondary);
  border-radius: var(--radius-full);
  transition:
    transform var(--transition-base),
    opacity var(--transition-base);
}

/* Mobile nav open state */
.nav-toggle[aria-expanded='true'] .nav-toggle-bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav-toggle[aria-expanded='true'] .nav-toggle-bar:nth-child(2) {
  opacity: 0;
}
.nav-toggle[aria-expanded='true'] .nav-toggle-bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ============================================================
           5. HERO SECTION
           ============================================================ */

.hero-section {
  position: relative;
  overflow: hidden;
  padding: var(--space-24) var(--space-6) var(--space-20);
  background: linear-gradient(
    160deg,
    rgba(49, 46, 129, 0.3) 0%,
    rgba(15, 17, 23, 0) 50%,
    rgba(15, 17, 23, 0) 100%
  );
}

/* Radial glow behind hero */
.hero-section::before {
  content: '';
  position: absolute;
  top: -20%;
  left: 50%;
  transform: translateX(-50%);
  width: 80vw;
  height: 80vw;
  max-width: 900px;
  max-height: 900px;
  background: radial-gradient(
    ellipse at center,
    rgba(99, 102, 241, 0.12) 0%,
    rgba(99, 102, 241, 0.04) 40%,
    transparent 70%
  );
  pointer-events: none;
}

.hero-inner {
  position: relative;
  max-width: var(--max-width-article);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-6);
}

/* Tag row */
.hero-tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  justify-content: center;
}

.hero-tag {
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-primary-light);
  background: rgba(129, 140, 248, 0.12);
  border: 1px solid rgba(129, 140, 248, 0.25);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

/* Title */
.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(var(--text-4xl), 7vw, var(--text-6xl));
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: #fff;
  background: linear-gradient(135deg, #fff 30%, var(--color-primary-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-family: var(--font-serif);
  font-size: clamp(var(--text-xl), 3vw, var(--text-3xl));
  font-weight: 400;
  font-style: italic;
  color: var(--color-text-secondary);
  margin-top: calc(-1 * var(--space-4));
}

.hero-hook {
  max-width: 60ch;
  font-size: var(--text-lg);
  color: var(--color-text-secondary);
  line-height: 1.8;
}

/* Ladder motif */
.hero-ladder-motif {
  display: flex;
  flex-direction: column-reverse;
  align-items: center;
  gap: 0;
  margin: var(--space-4) 0;
}

.ladder-rung {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 56px;
  height: 56px;
  font-size: var(--text-xl);
  font-weight: 700;
  border-radius: var(--radius-lg);
  border: 2px solid;
  position: relative;
  transition: transform var(--transition-base);
  cursor: default;
}

.ladder-rung::after {
  content: '';
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%);
  width: 2px;
  height: 20px;
}

.ladder-rung:last-child::after {
  display: none;
}

.ladder-rung:hover {
  transform: scale(1.1);
}

.ladder-rung--integer {
  color: var(--color-integer);
  border-color: var(--color-integer);
  background: rgba(96, 165, 250, 0.1);
}
.ladder-rung--integer::after {
  background: var(--color-integer);
}

.ladder-rung--rational {
  color: var(--color-rational);
  border-color: var(--color-rational);
  background: rgba(52, 211, 153, 0.1);
}
.ladder-rung--rational::after {
  background: var(--color-rational);
}

.ladder-rung--algebraic {
  color: var(--color-algebraic);
  border-color: var(--color-algebraic);
  background: rgba(245, 158, 11, 0.1);
}
.ladder-rung--algebraic::after {
  background: var(--color-algebraic);
}

.ladder-rung--real {
  color: var(--color-real);
  border-color: var(--color-real);
  background: rgba(248, 113, 113, 0.1);
}
.ladder-rung--real::after {
  background: var(--color-real);
}

.ladder-rung--complex {
  color: var(--color-complex);
  border-color: var(--color-complex);
  background: rgba(192, 132, 252, 0.1);
}

/* Hero meta */
.hero-meta {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

.hero-meta-divider {
  opacity: 0.4;
}

/* ============================================================
           6. ARTICLE MAIN LAYOUT
           ============================================================ */

.article-main {
  max-width: var(--max-width-article);
  margin: 0 auto;
  padding: 0 var(--space-6) var(--space-24);
}

.article-body {
  display: flex;
  flex-direction: column;
  gap: 0;
}

/* ============================================================
           7. ARTICLE CAVEAT / FRAMING NOTE
           ============================================================ */

.article-caveat {
  margin: var(--space-12) 0;
  background: rgba(129, 140, 248, 0.06);
  border: 1px solid rgba(129, 140, 248, 0.2);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.caveat-inner {
  padding: var(--space-6) var(--space-8);
}

.caveat-label {
  display: block;
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-primary-light);
  margin-bottom: var(--space-3);
}

.caveat-text {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: 1.8;
  font-style: italic;
  max-width: 70ch;
}

/* ============================================================
           8. ARTICLE SECTIONS — BASE
           ============================================================ */

.article-section {
  padding: var(--space-16) 0;
  border-bottom: 1px solid var(--color-border);
}

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

.section-inner {
  max-width: var(--max-width-content);
  margin: 0 auto;
}

/* Wide sections override */
.article-section--highlighted .section-inner,
.article-section--ladder .section-inner,
.article-section--philosophy .section-inner {
  max-width: 100%;
}

.article-section--highlighted {
  background: linear-gradient(180deg, rgba(49, 46, 129, 0.08) 0%, transparent 100%);
  border-radius: var(--radius-xl);
  padding: var(--space-16) var(--space-8);
  margin: var(--space-4) 0;
}

.article-section--philosophy {
  background: rgba(22, 27, 39, 0.6);
  border-radius: var(--radius-xl);
  padding: var(--space-16) var(--space-8);
  margin: var(--space-4) 0;
}

.article-section--closing {
  background: linear-gradient(135deg, rgba(49, 46, 129, 0.15) 0%, rgba(15, 17, 23, 0) 60%);
  border-radius: var(--radius-xl);
  padding: var(--space-16) var(--space-8);
}

/* Section headings */
.section-heading {
  font-family: var(--font-serif);
  font-size: clamp(var(--text-2xl), 4vw, var(--text-3xl));
  font-weight: 700;
  line-height: 1.2;
  color: #fff;
  margin-bottom: var(--space-8);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-border);
  position: relative;
}

.section-heading::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  width: 3rem;
  height: 2px;
  background: var(--color-primary);
  border-radius: var(--radius-full);
}

/* Section content */
.section-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

/* ============================================================
           9. ARTICLE PARAGRAPHS
           ============================================================ */

.article-paragraph {
  font-size: var(--text-lg);
  line-height: 1.85;
  color: var(--color-text-secondary);
  max-width: 70ch;
}

.article-paragraph--lead {
  font-size: var(--text-xl);
  color: var(--color-text-primary);
  font-weight: 400;
}

.article-paragraph--emphasis {
  font-size: var(--text-xl);
  font-style: italic;
  color: var(--color-primary-light);
  font-family: var(--font-serif);
}

/* ============================================================
           10. MECHANISM STEPS
           ============================================================ */

.mechanism-steps {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  align-items: start;
  gap: var(--space-4);
  margin: var(--space-8) 0;
  padding: var(--space-8);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
}

.mechanism-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-3);
  padding: var(--space-6);
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  transition:
    border-color var(--transition-base),
    transform var(--transition-base);
}

.mechanism-step:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
}

.mechanism-step[data-step='1'] {
  border-top: 3px solid var(--color-integer);
}
.mechanism-step[data-step='2'] {
  border-top: 3px solid var(--color-algebraic);
}
.mechanism-step[data-step='3'] {
  border-top: 3px solid var(--color-complex);
}

.mechanism-step-icon {
  font-size: var(--text-3xl);
  line-height: 1;
  opacity: 0.6;
}

.mechanism-step[data-step='1'] .mechanism-step-icon {
  color: var(--color-integer);
}
.mechanism-step[data-step='2'] .mechanism-step-icon {
  color: var(--color-algebraic);
}
.mechanism-step[data-step='3'] .mechanism-step-icon {
  color: var(--color-complex);
}

.mechanism-step-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: #fff;
  letter-spacing: 0.02em;
}

.mechanism-step-description {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.mechanism-step-arrow {
  font-size: var(--text-2xl);
  color: var(--color-text-muted);
  align-self: center;
  padding-top: var(--space-6);
}

/* ============================================================
           11. INLINE ASIDES
           ============================================================ */

.inline-aside {
  background: rgba(22, 27, 39, 0.8);
  border: 1px solid var(--color-border);
  border-left: 3px solid var(--color-primary);
  border-radius: var(--radius-lg);
  padding: var(--space-5) var(--space-6);
  margin: var(--space-4) 0;
}

.inline-aside--cardinality {
  border-left-color: var(--color-info);
}

.inline-aside-heading {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-primary-light);
  margin-bottom: var(--space-2);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.inline-aside--cardinality .inline-aside-heading {
  color: var(--color-info);
}

.inline-aside-text {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: 1.75;
}

/* ============================================================
           12. OPERATOR COMPARISON CARDS
           ============================================================ */

.operator-comparison {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-6);
  margin: var(--space-8) 0;
}

.operator-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  transition:
    border-color var(--transition-base),
    box-shadow var(--transition-base);
}

.operator-card:hover {
  box-shadow: var(--shadow-md);
}

.operator-card--algebraic {
  border-top: 3px solid var(--color-rational);
}

.operator-card--algebraic:hover {
  border-color: var(--color-rational);
}

.operator-card--transcendental {
  border-top: 3px solid var(--color-real);
}

.operator-card--transcendental:hover {
  border-color: var(--color-real);
}

.operator-card-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: #fff;
}

.operator-card--algebraic .operator-card-title {
  color: var(--color-rational);
}
.operator-card--transcendental .operator-card-title {
  color: var(--color-real);
}

.operator-card-subtitle {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
  margin-top: calc(-1 * var(--space-3));
}

.operator-card-examples {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.operator-example {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  padding: var(--space-3);
  background: var(--color-surface);
  border-radius: var(--radius-md);
}

.operator-example-question {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-text-primary);
  font-weight: 600;
}

.operator-example-answer {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

.operator-card-note {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
  padding-top: var(--space-2);
  border-top: 1px solid var(--color-border);
}

/* ============================================================
           13. LADDER DIAGRAM
           ============================================================ */

.ladder-diagram {
  display: flex;
  flex-direction: column;
  gap: 0;
  margin: var(--space-10) 0;
  position: relative;
}

/* Vertical spine */
.ladder-diagram::before {
  content: '';
  position: absolute;
  left: 28px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: linear-gradient(
    to bottom,
    var(--color-integer),
    var(--color-rational),
    var(--color-algebraic),
    var(--color-real),
    var(--color-complex)
  );
  opacity: 0.3;
  z-index: 0;
}

/* Ladder levels */
.ladder-level {
  display: flex;
  align-items: flex-start;
  gap: var(--space-5);
  padding: var(--space-6);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  position: relative;
  z-index: 1;
  transition:
    border-color var(--transition-base),
    box-shadow var(--transition-base),
    transform var(--transition-base);
  cursor: default;
}

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

.ladder-level--0 {
  border-left: 4px solid var(--color-integer);
}
.ladder-level--1 {
  border-left: 4px solid var(--color-rational);
}
.ladder-level--2 {
  border-left: 4px solid var(--color-algebraic);
}
.ladder-level--3 {
  border-left: 4px solid var(--color-real);
}
.ladder-level--4 {
  border-left: 4px solid var(--color-complex);
}

.ladder-level--0:hover {
  border-color: var(--color-integer);
}
.ladder-level--1:hover {
  border-color: var(--color-rational);
}
.ladder-level--2:hover {
  border-color: var(--color-algebraic);
}
.ladder-level--3:hover {
  border-color: var(--color-real);
}
.ladder-level--4:hover {
  border-color: var(--color-complex);
}

/* Level marker */
.ladder-level-marker {
  flex-shrink: 0;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: var(--text-sm);
  position: relative;
  z-index: 2;
}

.ladder-level--0 .ladder-level-marker {
  background: rgba(96, 165, 250, 0.15);
  color: var(--color-integer);
  border: 2px solid var(--color-integer);
}
.ladder-level--1 .ladder-level-marker {
  background: rgba(52, 211, 153, 0.15);
  color: var(--color-rational);
  border: 2px solid var(--color-rational);
}
.ladder-level--2 .ladder-level-marker {
  background: rgba(245, 158, 11, 0.15);
  color: var(--color-algebraic);
  border: 2px solid var(--color-algebraic);
}
.ladder-level--3 .ladder-level-marker {
  background: rgba(248, 113, 113, 0.15);
  color: var(--color-real);
  border: 2px solid var(--color-real);
}
.ladder-level--4 .ladder-level-marker {
  background: rgba(192, 132, 252, 0.15);
  color: var(--color-complex);
  border: 2px solid var(--color-complex);
}

.ladder-level-number {
  line-height: 1;
}

/* Level content */
.ladder-level-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.ladder-level-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.ladder-level-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: #fff;
}

.ladder-level-symbol {
  font-size: var(--text-3xl);
  font-weight: 700;
  line-height: 1;
  opacity: 0.7;
}

.ladder-level--0 .ladder-level-symbol {
  color: var(--color-integer);
}
.ladder-level--1 .ladder-level-symbol {
  color: var(--color-rational);
}
.ladder-level--2 .ladder-level-symbol {
  color: var(--color-algebraic);
}
.ladder-level--3 .ladder-level-symbol {
  color: var(--color-real);
}
.ladder-level--4 .ladder-level-symbol {
  color: var(--color-complex);
}

.ladder-level-description {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  line-height: 1.75;
}

/* Level tags */
.ladder-level-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.ladder-level-tag {
  font-size: var(--text-xs);
  font-weight: 600;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  border: 1px solid;
}

.ladder-level--0 .ladder-level-tag {
  color: var(--color-integer);
  border-color: rgba(96, 165, 250, 0.3);
  background: rgba(96, 165, 250, 0.08);
}
.ladder-level--1 .ladder-level-tag {
  color: var(--color-rational);
  border-color: rgba(52, 211, 153, 0.3);
  background: rgba(52, 211, 153, 0.08);
}
.ladder-level--2 .ladder-level-tag {
  color: var(--color-algebraic);
  border-color: rgba(245, 158, 11, 0.3);
  background: rgba(245, 158, 11, 0.08);
}
.ladder-level--3 .ladder-level-tag {
  color: var(--color-real);
  border-color: rgba(248, 113, 113, 0.3);
  background: rgba(248, 113, 113, 0.08);
}
.ladder-level--4 .ladder-level-tag {
  color: var(--color-complex);
  border-color: rgba(192, 132, 252, 0.3);
  background: rgba(192, 132, 252, 0.08);
}

/* Level note */
.ladder-level-note {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  background: rgba(245, 158, 11, 0.06);
  border: 1px solid rgba(245, 158, 11, 0.15);
  border-radius: var(--radius-md);
  padding: var(--space-3) var(--space-4);
  line-height: 1.7;
}

/* Level milestone */
.ladder-level-milestone {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-real);
  font-weight: 600;
}

.milestone-icon {
  font-size: var(--text-base);
}

/* Connectors between levels */
.ladder-connector {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  padding: var(--space-2) var(--space-6) var(--space-2) calc(28px + var(--space-5) + var(--space-6));
  gap: var(--space-1);
  position: relative;
  z-index: 1;
}

.ladder-connector-label {
  font-size: var(--text-xs);
  font-family: var(--font-mono);
  color: var(--color-text-muted);
  background: var(--color-bg);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  border: 1px solid var(--color-border);
}

.ladder-connector--new-op .ladder-connector-label {
  color: var(--color-real);
  border-color: rgba(248, 113, 113, 0.3);
  background: rgba(248, 113, 113, 0.06);
}

.ladder-connector-badge {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-real);
  background: rgba(248, 113, 113, 0.12);
  border: 1px solid rgba(248, 113, 113, 0.3);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

/* ============================================================
           14. ACCESSIBILITY SPECTRUM
           ============================================================ */

.accessibility-spectrum {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  margin: var(--space-6) 0;
}

.accessibility-spectrum-header {
  margin-bottom: var(--space-4);
}

.accessibility-spectrum-label {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

.accessibility-spectrum-bar {
  display: flex;
  height: 64px;
  border-radius: var(--radius-md);
  overflow: hidden;
  gap: 2px;
}

.accessibility-segment {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: var(--space-1);
  flex: 0 0 var(--segment-width);
  padding: var(--space-2);
  text-align: center;
  transition: flex var(--transition-slow);
}

.accessibility-segment:hover {
  flex: 0 0 calc(var(--segment-width) + 5%);
}

.accessibility-segment--elementary {
  background: linear-gradient(135deg, rgba(52, 211, 153, 0.25), rgba(52, 211, 153, 0.15));
  border: 1px solid rgba(52, 211, 153, 0.3);
  border-radius: var(--radius-md) 0 0 var(--radius-md);
}

.accessibility-segment--horizon {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.25), rgba(245, 158, 11, 0.15));
  border: 1px solid rgba(245, 158, 11, 0.3);
}

.accessibility-segment--advanced {
  background: linear-gradient(135deg, rgba(248, 113, 113, 0.25), rgba(248, 113, 113, 0.15));
  border: 1px solid rgba(248, 113, 113, 0.3);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.accessibility-segment-label {
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.accessibility-segment--elementary .accessibility-segment-label {
  color: var(--color-rational);
}
.accessibility-segment--horizon .accessibility-segment-label {
  color: var(--color-algebraic);
}
.accessibility-segment--advanced .accessibility-segment-label {
  color: var(--color-real);
}

.accessibility-segment-range {
  font-size: var(--text-xs);
  font-family: var(--font-mono);
  color: var(--color-text-muted);
}

/* ============================================================
           15. PULL QUOTE
           ============================================================ */

.pull-quote {
  margin: var(--space-10) 0;
  padding: var(--space-8) var(--space-10);
  border-left: 4px solid var(--color-primary);
  background: linear-gradient(135deg, rgba(49, 46, 129, 0.15) 0%, rgba(49, 46, 129, 0.05) 100%);
  border-radius: 0 var(--radius-xl) var(--radius-xl) 0;
  position: relative;
}

.pull-quote::before {
  content: '"';
  position: absolute;
  top: -0.2em;
  left: var(--space-6);
  font-family: var(--font-serif);
  font-size: 6rem;
  line-height: 1;
  color: var(--color-primary);
  opacity: 0.2;
  pointer-events: none;
}

.pull-quote-text {
  font-family: var(--font-serif);
  font-size: clamp(var(--text-xl), 3vw, var(--text-2xl));
  font-style: italic;
  color: var(--color-text-primary);
  line-height: 1.6;
  position: relative;
  z-index: 1;
}

/* ============================================================
           16. PATTERN EXAMPLES GRID
           ============================================================ */

.pattern-examples {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-8);
  margin: var(--space-8) 0;
}

.pattern-examples-heading {
  font-size: var(--text-xl);
  font-weight: 700;
  color: #fff;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-border);
}

.pattern-examples-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-5);
}

.pattern-example-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  transition:
    border-color var(--transition-base),
    transform var(--transition-base);
}

.pattern-example-card:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
}

.pattern-example-icon {
  font-size: var(--text-3xl);
  color: var(--color-primary-light);
  line-height: 1;
  opacity: 0.7;
}

.pattern-example-title {
  font-size: var(--text-base);
  font-weight: 700;
  color: #fff;
}

.pattern-example-text {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: 1.75;
}

/* ============================================================
           17. PHILOSOPHY READINGS
           ============================================================ */

.philosophy-readings {
  margin: var(--space-8) 0;
}

.philosophy-readings-heading {
  font-size: var(--text-xl);
  font-weight: 700;
  color: #fff;
  margin-bottom: var(--space-4);
}

.philosophy-readings-intro {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-6);
  max-width: 65ch;
}

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

.philosophy-reading {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  transition: border-color var(--transition-base);
}

.philosophy-reading[data-reading='realist'] {
  border-left: 4px solid var(--color-integer);
}
.philosophy-reading[data-reading='constructivist'] {
  border-left: 4px solid var(--color-rational);
}
.philosophy-reading[data-reading='pragmatist'] {
  border-left: 4px solid var(--color-algebraic);
}

.philosophy-reading[data-reading='realist']:hover {
  border-color: var(--color-integer);
}
.philosophy-reading[data-reading='constructivist']:hover {
  border-color: var(--color-rational);
}
.philosophy-reading[data-reading='pragmatist']:hover {
  border-color: var(--color-algebraic);
}

.philosophy-reading-title {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.philosophy-reading-label {
  font-size: var(--text-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

.philosophy-reading[data-reading='realist'] .philosophy-reading-label {
  color: var(--color-integer);
  background: rgba(96, 165, 250, 0.1);
  border: 1px solid rgba(96, 165, 250, 0.25);
}

.philosophy-reading[data-reading='constructivist'] .philosophy-reading-label {
  color: var(--color-rational);
  background: rgba(52, 211, 153, 0.1);
  border: 1px solid rgba(52, 211, 153, 0.25);
}

.philosophy-reading[data-reading='pragmatist'] .philosophy-reading-label {
  color: var(--color-algebraic);
  background: rgba(245, 158, 11, 0.1);
  border: 1px solid rgba(245, 158, 11, 0.25);
}

.philosophy-reading-text {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  line-height: 1.8;
}

.philosophy-readings-conclusion {
  margin-top: var(--space-6);
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  font-style: italic;
  max-width: 65ch;
}

/* ============================================================
           18. COMPARISON TABLE
           ============================================================ */

.comparison-table-wrapper {
  overflow-x: auto;
  margin: var(--space-8) 0;
  border-radius: var(--radius-xl);
  border: 1px solid var(--color-border);
  -webkit-overflow-scrolling: touch;
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--text-sm);
}

.comparison-table-caption {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-text-muted);
  text-align: left;
  padding: var(--space-4) var(--space-6);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.comparison-table-header {
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-muted);
  padding: var(--space-4) var(--space-6);
  text-align: left;
  background: var(--color-bg-card);
  border-bottom: 1px solid var(--color-border);
  white-space: nowrap;
}

.comparison-table-row {
  border-bottom: 1px solid var(--color-border);
  transition: background var(--transition-fast);
}

.comparison-table-row:last-child {
  border-bottom: none;
}

.comparison-table-row:hover {
  background: rgba(129, 140, 248, 0.05);
}

/* The big jump row */
.comparison-table-row--jump {
  background: rgba(248, 113, 113, 0.04);
  border-top: 2px solid rgba(248, 113, 113, 0.3);
}

.comparison-table-row--jump:hover {
  background: rgba(248, 113, 113, 0.08);
}

.comparison-table-cell {
  padding: var(--space-4) var(--space-6);
  color: var(--color-text-secondary);
  vertical-align: middle;
}

.comparison-table-cell--name {
  font-weight: 600;
  color: var(--color-text-primary);
  font-family: var(--font-mono);
  white-space: nowrap;
}

.comparison-table-cell--cardinality {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
}

.comparison-table-cell--level {
  font-weight: 700;
  text-align: center;
}

.comparison-table-cell--op {
  font-style: italic;
}

/* ============================================================
           19. SUMMARY STATEMENT
           ============================================================ */

.summary-statement {
  background: linear-gradient(135deg, rgba(49, 46, 129, 0.25) 0%, rgba(99, 102, 241, 0.1) 100%);
  border: 1px solid rgba(129, 140, 248, 0.3);
  border-radius: var(--radius-2xl);
  padding: var(--space-10) var(--space-12);
  margin: var(--space-8) 0;
  position: relative;
  overflow: hidden;
}

.summary-statement::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse at top left, rgba(129, 140, 248, 0.1) 0%, transparent 60%);
  pointer-events: none;
}

.summary-statement-text {
  font-family: var(--font-serif);
  font-size: clamp(var(--text-lg), 2.5vw, var(--text-2xl));
  line-height: 1.7;
  color: var(--color-text-primary);
  position: relative;
  z-index: 1;
}

/* ============================================================
           20. FURTHER READING / KEY CONCEPTS ASIDE
           ============================================================ */

.further-reading {
  background: var(--color-bg-alt);
  border-top: 1px solid var(--color-border);
  padding: var(--space-16) var(--space-6);
}

.further-reading-inner {
  max-width: var(--max-width-article);
  margin: 0 auto;
}

.further-reading-heading {
  font-family: var(--font-serif);
  font-size: var(--text-2xl);
  font-weight: 700;
  color: #fff;
  margin-bottom: var(--space-8);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-border);
}

.concept-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-4);
}

.concept-item {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-5);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition:
    border-color var(--transition-base),
    transform var(--transition-base);
}

.concept-item:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
}

.concept-term {
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-primary-light);
}

.concept-description {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ============================================================
           21. SITE FOOTER
           ============================================================ */

.site-footer {
  background: var(--color-bg);
  border-top: 1px solid var(--color-border);
  padding: var(--space-12) var(--space-6);
}

.site-footer-inner {
  max-width: var(--max-width-wide);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: start;
  gap: var(--space-10);
}

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

.footer-brand-name {
  font-family: var(--font-serif);
  font-size: var(--text-lg);
  font-weight: 700;
  color: #fff;
}

.footer-brand-tagline {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
}

.footer-nav-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  align-items: center;
}

.footer-nav-link {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-nav-link:hover {
  color: var(--color-primary-light);
}

.footer-meta {
  text-align: right;
}

.footer-meta-text {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
  max-width: 30ch;
  margin-left: auto;
}

/* ============================================================
           22. BACK TO TOP BUTTON
           ============================================================ */

.back-to-top {
  position: fixed;
  bottom: var(--space-8);
  right: var(--space-8);
  width: 48px;
  height: 48px;
  background: var(--color-primary-dark);
  color: #fff;
  border: none;
  border-radius: var(--radius-full);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-xl);
  box-shadow: var(--shadow-lg);
  transition:
    background var(--transition-fast),
    transform var(--transition-fast),
    opacity var(--transition-base);
  z-index: var(--z-top);
  opacity: 1;
}

.back-to-top[hidden] {
  display: none;
}

.back-to-top:hover {
  background: var(--color-primary);
  transform: translateY(-3px);
}

.back-to-top:active {
  transform: translateY(0);
}

.back-to-top-icon {
  line-height: 1;
}

/* ============================================================
           23. SCROLLBAR STYLING
           ============================================================ */

::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

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

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

::-webkit-scrollbar-thumb:hover {
  background: var(--color-border-light);
}

/* ============================================================
           24. RESPONSIVE — TABLET (max 1024px)
           ============================================================ */

@media (max-width: 1024px) {
  .mechanism-steps {
    grid-template-columns: 1fr;
    gap: var(--space-3);
  }

  .mechanism-step-arrow {
    transform: rotate(90deg);
    align-self: center;
    padding-top: 0;
  }

  .pattern-examples-grid {
    grid-template-columns: 1fr 1fr;
  }

  .site-footer-inner {
    grid-template-columns: 1fr 1fr;
    grid-template-rows: auto auto;
  }

  .footer-meta {
    grid-column: 1 / -1;
    text-align: left;
  }

  .footer-meta-text {
    margin-left: 0;
    max-width: 100%;
  }
}

/* ============================================================
           25. RESPONSIVE — MOBILE (max 768px)
           ============================================================ */

@media (max-width: 768px) {
  /* Nav */
  .nav-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    background: var(--color-bg-alt);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-4);
    gap: var(--space-1);
    z-index: var(--z-nav);
  }

  .nav-menu.is-open {
    display: flex;
  }

  .nav-toggle {
    display: flex;
  }

  .site-nav {
    position: relative;
    flex-wrap: wrap;
  }

  /* Hero */
  .hero-section {
    padding: var(--space-16) var(--space-4) var(--space-12);
  }

  .hero-ladder-motif {
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: center;
  }

  .ladder-rung::after {
    display: none;
  }

  /* Article */
  .article-main {
    padding: 0 var(--space-4) var(--space-16);
  }

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

  .article-section--highlighted,
  .article-section--philosophy,
  .article-section--closing {
    padding: var(--space-10) var(--space-4);
  }

  /* Operator comparison */
  .operator-comparison {
    grid-template-columns: 1fr;
  }

  /* Pattern examples */
  .pattern-examples-grid {
    grid-template-columns: 1fr;
  }

  /* Ladder diagram */
  .ladder-diagram::before {
    left: 20px;
  }

  .ladder-level {
    flex-direction: column;
    gap: var(--space-4);
  }

  .ladder-level-header {
    flex-direction: row;
  }

  .ladder-connector {
    padding-left: var(--space-6);
  }

  /* Summary */
  .summary-statement {
    padding: var(--space-8) var(--space-6);
  }

  /* Footer */
  .site-footer-inner {
    grid-template-columns: 1fr;
    gap: var(--space-8);
  }

  .footer-nav-list {
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: flex-start;
    align-items: flex-start;
  }

  .footer-meta {
    text-align: left;
  }

  .footer-meta-text {
    margin-left: 0;
    max-width: 100%;
  }

  /* Back to top */
  .back-to-top {
    bottom: var(--space-5);
    right: var(--space-5);
    width: 42px;
    height: 42px;
  }

  /* Pull quote */
  .pull-quote {
    padding: var(--space-6) var(--space-6);
  }

  /* Accessibility spectrum */
  .accessibility-spectrum-bar {
    flex-direction: column;
    height: auto;
  }

  .accessibility-segment {
    flex: 1 0 auto;
    width: 100%;
    padding: var(--space-3);
    border-radius: var(--radius-md) !important;
  }

  .accessibility-segment:hover {
    flex: 1 0 auto;
  }
}

/* ============================================================
           26. RESPONSIVE — SMALL MOBILE (max 480px)
           ============================================================ */

@media (max-width: 480px) {
  .hero-tag-row {
    gap: var(--space-1);
  }

  .hero-tag {
    font-size: 0.65rem;
  }

  .mechanism-steps {
    padding: var(--space-5);
  }

  .mechanism-step {
    padding: var(--space-4);
  }

  .ladder-level {
    padding: var(--space-4);
  }

  .ladder-level-symbol {
    font-size: var(--text-2xl);
  }

  .concept-list {
    grid-template-columns: 1fr;
  }

  .comparison-table-cell {
    padding: var(--space-3) var(--space-4);
  }
}

/* ============================================================
           27. PRINT STYLES
           ============================================================ */

@media print {
  .site-header,
  .nav-toggle,
  .back-to-top,
  .further-reading {
    display: none;
  }

  body {
    background: #fff;
    color: #000;
  }

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

  .hero-section {
    background: none;
    padding: 2rem 0;
  }

  .hero-title {
    -webkit-text-fill-color: #000;
    color: #000;
  }

  .ladder-level,
  .mechanism-step,
  .operator-card,
  .pattern-example-card {
    border: 1px solid #ccc;
    break-inside: avoid;
  }
}

/* ============================================================
           28. 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;
  }
}