/* ============================================================
   THE FIVE PILLARS — Swiss-Modernist Editorial
   Instrument Serif headings · Source Sans 3 body
   Warm off-white · Navy ink · Coral accent
   ============================================================ */

/* ---------- Design Tokens ---------- */
:root,
[data-theme='light'] {
  /* Surfaces — warm off-white paper */
  --color-bg: #f4f1ea;
  --color-surface: #faf8f2;
  --color-surface-2: #fffdf8;
  --color-surface-offset: #ece8de;
  --color-divider: #ddd7c9;
  --color-border: #d2ccbc;

  /* Ink — deep navy */
  --color-text: #1a2238;
  --color-text-muted: #5a6178;
  --color-text-faint: #9aa0b0;
  --color-text-inverse: #f4f1ea;

  /* Accent — coral */
  --color-accent: #e8624a;
  --color-accent-hover: #d34f38;
  --color-accent-soft: #f6d9d1;

  /* Navy block */
  --color-navy: #1a2238;
  --color-navy-2: #232c47;

  /* Type */
  --font-display: 'Instrument Serif', Georgia, 'Times New Roman', serif;
  --font-body: 'Source Sans 3', system-ui, -apple-system, sans-serif;
  --font-mono: 'IBM Plex Mono', ui-monospace, 'SFMono-Regular', monospace;

  --text-xs: clamp(0.75rem, 0.7rem + 0.2vw, 0.8125rem);
  --text-sm: clamp(0.875rem, 0.83rem + 0.2vw, 0.9375rem);
  --text-base: clamp(1.0625rem, 1rem + 0.3vw, 1.1875rem);
  --text-lg: clamp(1.25rem, 1.1rem + 0.6vw, 1.5rem);
  --text-xl: clamp(1.75rem, 1.3rem + 1.6vw, 2.75rem);
  --text-2xl: clamp(2.5rem, 1.6rem + 3vw, 4.25rem);
  --text-hero: clamp(3.25rem, 1rem + 8vw, 8.5rem);

  /* 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;

  --radius-sm: 2px;
  --radius-md: 4px;

  --content-narrow: 680px;
  --content-default: 1080px;
  --content-wide: 1340px;

  --transition-interactive: 200ms cubic-bezier(0.16, 1, 0.3, 1);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);

  --shadow-sm: 0 1px 3px rgba(26, 34, 56, 0.06);
  --shadow-md: 0 8px 28px rgba(26, 34, 56, 0.1);
  --shadow-lg: 0 20px 50px rgba(26, 34, 56, 0.14);
}

[data-theme='dark'] {
  --color-bg: #14161f;
  --color-surface: #1a1d28;
  --color-surface-2: #20232f;
  --color-surface-offset: #1d2029;
  --color-divider: #2c2f3b;
  --color-border: #353947;

  --color-text: #e7e4da;
  --color-text-muted: #9ba0ae;
  --color-text-faint: #686d7c;
  --color-text-inverse: #14161f;

  --color-accent: #f47a63;
  --color-accent-hover: #f68f7b;
  --color-accent-soft: #3a2620;

  --color-navy: #20232f;
  --color-navy-2: #272b39;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 8px 28px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.5);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg: #14161f;
    --color-surface: #1a1d28;
    --color-surface-2: #20232f;
    --color-surface-offset: #1d2029;
    --color-divider: #2c2f3b;
    --color-border: #353947;
    --color-text: #e7e4da;
    --color-text-muted: #9ba0ae;
    --color-text-faint: #686d7c;
    --color-text-inverse: #14161f;
    --color-accent: #f47a63;
    --color-accent-hover: #f68f7b;
    --color-accent-soft: #3a2620;
    --color-navy: #20232f;
    --color-navy-2: #272b39;
  }
}

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

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
  scroll-padding-top: 6rem;
}

body {
  min-height: 100dvh;
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: 400;
  line-height: 1.68;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color 400ms var(--ease-out), color 400ms var(--ease-out);
}

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

h1,
h2,
h3,
h4 {
  font-family: var(--font-display);
  font-weight: 400;
  line-height: 1.04;
  letter-spacing: -0.01em;
  text-wrap: balance;
  color: var(--color-text);
}

p {
  text-wrap: pretty;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--transition-interactive);
}

::selection {
  background: var(--color-accent);
  color: #fff;
}

:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

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

.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;
}

@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;
  }
}

/* ---------- Reading Progress Bar ---------- */
.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 100%;
  transform-origin: 0 50%;
  transform: scaleX(0);
  background: var(--color-accent);
  z-index: 200;
}

/* ---------- Header ---------- */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-4) clamp(var(--space-5), 5vw, var(--space-16));
  background: color-mix(in srgb, var(--color-bg) 86%, transparent);
  backdrop-filter: blur(14px) saturate(1.2);
  -webkit-backdrop-filter: blur(14px) saturate(1.2);
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition-interactive), box-shadow var(--transition-interactive);
}

.header--scrolled {
  border-bottom-color: var(--color-divider);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-family: var(--font-body);
  font-weight: 600;
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.brand svg {
  flex-shrink: 0;
  color: var(--color-accent);
}

.brand-text {
  color: var(--color-text);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.byline-link {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  padding: var(--space-2) var(--space-3);
}

.byline-link:hover {
  color: var(--color-accent);
}

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

.icon-btn {
  display: grid;
  place-items: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  transition: color var(--transition-interactive), background var(--transition-interactive);
}

.icon-btn:hover {
  color: var(--color-text);
  background: var(--color-surface-offset);
}

/* ---------- Layout ---------- */
.wrap {
  width: min(100% - 2.5rem, var(--content-wide));
  margin-inline: auto;
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding-block: clamp(var(--space-12), 7vw, var(--space-24)) clamp(var(--space-16), 9vw, var(--space-32));
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.35fr 0.65fr;
  gap: clamp(var(--space-8), 5vw, var(--space-20));
  align-items: center;
}

.hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: var(--space-6);
}

.hero-kicker::before {
  content: '';
  width: 40px;
  height: 1px;
  background: var(--color-accent);
}

.hero h1 {
  font-size: var(--text-hero);
  line-height: 0.92;
  margin-bottom: var(--space-6);
}

.hero h1 em {
  font-style: italic;
  color: var(--color-accent);
}

.hero-lede {
  font-size: var(--text-lg);
  line-height: 1.5;
  color: var(--color-text-muted);
  max-width: 34ch;
  margin-bottom: var(--space-8);
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-6);
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-divider);
}

.hero-meta-item {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.hero-meta-item .label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-text-faint);
}

.hero-meta-item .value {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
}

.hero-meta-item .value a:hover {
  color: var(--color-accent);
}

.hero-figure {
  position: relative;
}

.hero-figure img {
  width: 100%;
  border-radius: var(--radius-md);
}

.hero-figure::after {
  content: '';
  position: absolute;
  inset: 0;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  pointer-events: none;
  mix-blend-mode: multiply;
}

/* ---------- Main Grid: TOC + Content ---------- */
.layout {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  gap: clamp(var(--space-8), 5vw, var(--space-20));
  align-items: start;
  padding-bottom: var(--space-32);
}

/* ---------- Sticky TOC ---------- */
.toc {
  position: sticky;
  top: 6rem;
  align-self: start;
}

.toc-title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-text-faint);
  padding-bottom: var(--space-4);
  margin-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-divider);
}

.toc-list {
  list-style: none;
  display: flex;
  flex-direction: column;
}

.toc-link {
  display: flex;
  gap: var(--space-3);
  padding: var(--space-2) 0;
  font-size: var(--text-sm);
  line-height: 1.35;
  color: var(--color-text-muted);
  border-left: 2px solid transparent;
  padding-left: var(--space-4);
  margin-left: -2px;
  transition: color var(--transition-interactive), border-color var(--transition-interactive);
}

.toc-link .num {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  flex-shrink: 0;
  padding-top: 2px;
  transition: color var(--transition-interactive);
}

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

.toc-link.is-active {
  color: var(--color-accent);
  border-left-color: var(--color-accent);
  font-weight: 600;
}

.toc-link.is-active .num {
  color: var(--color-accent);
}

/* ---------- Article ---------- */
.article {
  min-width: 0;
}

.section {
  scroll-margin-top: 6rem;
  padding-block: clamp(var(--space-12), 6vw, var(--space-24));
  border-top: 1px solid var(--color-divider);
}

.section:first-child {
  border-top: none;
  padding-top: 0;
}

.section-head {
  margin-bottom: var(--space-10);
}

.section-index {
  display: flex;
  align-items: baseline;
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}

.section-num {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-accent);
  letter-spacing: 0.05em;
}

.section-tag {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-text-faint);
}

.section h2 {
  font-size: var(--text-xl);
  max-width: 20ch;
}

.section h3 {
  font-size: var(--text-lg);
  margin-top: var(--space-10);
  margin-bottom: var(--space-4);
  font-family: var(--font-body);
  font-weight: 700;
  letter-spacing: -0.005em;
}

.section p {
  margin-bottom: var(--space-5);
  max-width: 68ch;
}

.section p:last-child {
  margin-bottom: 0;
}

/* Section illustration */
.section-figure {
  margin: var(--space-10) 0;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.section-figure img {
  width: 100%;
}

.section-figure figcaption {
  padding: var(--space-3) var(--space-5);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.05em;
  color: var(--color-text-faint);
  border-top: 1px solid var(--color-border);
  background: var(--color-surface-2);
}

.section-figure figcaption b {
  color: var(--color-accent);
  font-weight: 500;
}

/* Lists */
.section ul.feature-list {
  list-style: none;
  display: grid;
  gap: var(--space-3);
  margin: var(--space-5) 0;
  max-width: 68ch;
}

.feature-list li {
  position: relative;
  padding-left: var(--space-6);
  line-height: 1.55;
}

.feature-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.65em;
  width: 8px;
  height: 8px;
  background: var(--color-accent);
}

.feature-list li b {
  font-weight: 700;
  color: var(--color-text);
}

/* Pull quote */
.pullquote {
  margin: var(--space-12) 0;
  padding: var(--space-8) clamp(var(--space-6), 4vw, var(--space-12));
  background: var(--color-navy);
  border-radius: var(--radius-md);
  position: relative;
  overflow: hidden;
}

.pullquote::before {
  content: '\201C';
  position: absolute;
  top: -0.3em;
  left: 0.1em;
  font-family: var(--font-display);
  font-size: 9rem;
  line-height: 1;
  color: var(--color-accent);
  opacity: 0.5;
}

.pullquote p {
  position: relative;
  font-family: var(--font-display);
  font-size: var(--text-lg);
  line-height: 1.3;
  color: #f4f1ea;
  max-width: 40ch;
  margin: 0;
}

.pullquote cite {
  display: block;
  margin-top: var(--space-4);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-style: normal;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-accent);
}

/* Stage timeline */
.stages {
  display: grid;
  gap: var(--space-3);
  margin: var(--space-8) 0;
  counter-reset: stage;
}

.stage {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-5);
  padding: var(--space-5) var(--space-6);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  align-items: start;
}

.stage-marker {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-accent);
  white-space: nowrap;
  padding-top: 2px;
}

.stage-body h4 {
  font-family: var(--font-body);
  font-weight: 700;
  font-size: var(--text-base);
  margin-bottom: var(--space-1);
}

.stage-body p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin: 0;
  line-height: 1.5;
}

.stage--ceiling {
  background: var(--color-navy);
  border-color: var(--color-navy);
}

.stage--ceiling .stage-body h4 {
  color: #f4f1ea;
}

.stage--ceiling .stage-body p {
  color: #b8bccb;
}

/* Funnel levels */
.levels {
  display: grid;
  gap: var(--space-3);
  margin: var(--space-8) 0;
}

.level {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-5);
  padding: var(--space-5) var(--space-6);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
}

.level-num {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  line-height: 1;
  color: var(--color-accent);
}

.level-body h4 {
  font-family: var(--font-body);
  font-weight: 700;
  font-size: var(--text-base);
  margin-bottom: var(--space-1);
}

.level-body p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin: 0;
  line-height: 1.5;
}

/* Citation markers */
.ref {
  font-family: var(--font-mono);
  font-size: 0.72em;
  font-weight: 500;
  color: var(--color-accent);
  vertical-align: super;
  line-height: 0;
  white-space: nowrap;
  margin-left: 1px;
}

.section p em,
.section li em {
  font-style: italic;
  color: var(--color-text);
}

/* References block */
.section-refs {
  margin-top: var(--space-6);
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  font-family: var(--font-mono);
  letter-spacing: 0.02em;
}

/* ---------- Footer ---------- */
.footer {
  border-top: 1px solid var(--color-divider);
  background: var(--color-surface);
}

.footer-inner {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: var(--space-8);
  align-items: end;
  padding-block: var(--space-16);
}

.footer h3 {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  margin-bottom: var(--space-3);
  max-width: 18ch;
}

.footer p {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  max-width: 48ch;
}

.footer-credit {
  text-align: right;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  letter-spacing: 0.04em;
  line-height: 1.8;
}

.footer-credit a {
  color: var(--color-accent);
  font-weight: 500;
}

.footer-credit a:hover {
  text-decoration: underline;
}

/* ---------- Scroll Reveal ---------- */
.reveal {
  opacity: 1;
}

@media (prefers-reduced-motion: no-preference) {
  .reveal {
    opacity: 0;
    transform: translateY(18px);
    transition: opacity 700ms var(--ease-out), transform 700ms var(--ease-out);
  }
  .reveal.is-visible {
    opacity: 1;
    transform: none;
  }
}

/* ---------- Mobile TOC toggle ---------- */
.toc-toggle {
  display: none;
}

/* ---------- Responsive ---------- */
@media (max-width: 980px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: var(--space-10);
  }
  .hero-figure {
    max-width: 360px;
    margin-inline: auto;
    order: -1;
  }
  .layout {
    grid-template-columns: 1fr;
    gap: var(--space-8);
  }
  .toc {
    position: static;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-5) var(--space-6);
  }
  .toc-list {
    max-height: 0;
    overflow: hidden;
    transition: max-height 350ms var(--ease-out);
  }
  .toc.is-open .toc-list {
    max-height: 600px;
  }
  .toc-title {
    margin-bottom: 0;
    padding-bottom: 0;
    border-bottom: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
  }
  .toc.is-open .toc-title {
    margin-bottom: var(--space-4);
    padding-bottom: var(--space-4);
    border-bottom: 1px solid var(--color-divider);
  }
  .toc-toggle {
    display: inline-block;
    transition: transform var(--transition-interactive);
  }
  .toc.is-open .toc-toggle {
    transform: rotate(180deg);
  }
}

@media (max-width: 620px) {
  .byline-link {
    display: none;
  }
  .footer-inner {
    grid-template-columns: 1fr;
    align-items: start;
  }
  .footer-credit {
    text-align: left;
  }
  .hero-meta {
    gap: var(--space-5);
  }
  .stage,
  .level {
    grid-template-columns: 1fr;
    gap: var(--space-2);
  }
}