/* ==========================================================================
   墨子 Mozi — "The Inkstone" Design System

   Every element earns its place. Mohist economy is not absence —
   it is the fierce concentration of resources where they matter most.
   ========================================================================== */

/* --- Tokens --- */
:root {
  /* Inkstone palette */
  --stone: #1c1915;
  --stone-warm: #2a2520;
  --paper: #faf8f3;
  --paper-tint: #f5f1ea;
  --paper-edge: #ece7dd;

  /* Ink tones */
  --ink: #141008;
  --ink-deep: #0a0804;
  --ink-light: #463d33;
  --ink-faint: #8a8275;
  --ink-ghost: #d4cfc6;

  /* Cinnabar & bronze */
  --cinnabar: #b03a2e;
  --cinnabar-dark: #8b2500;
  --bronze: #8b7537;
  --bronze-light: #a89255;

  /* Functional */
  --lost: #c4bdb0;

  /* Typography */
  --font-display: "Cormorant", "Georgia", serif;
  --font-body: "Spectral", "Georgia", "Times New Roman", serif;
  --font-body-weight: 500;
  --font-chinese: "Noto Serif SC", "Songti SC", "SimSun", serif;
  --font-ui: "Cormorant", "Georgia", serif;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 2rem;
  --space-xl: 3rem;
  --space-2xl: 5rem;
  --space-3xl: 8rem;

  /* Layout */
  --measure: 68rem;
  --reading-measure: 40rem;
}

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

/* --- Base --- */
html {
  font-size: 17px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  font-weight: 500;
  color: var(--ink);
  background: linear-gradient(180deg, var(--paper-tint) 0%, var(--paper) 40%);
  background-attachment: fixed;
  line-height: 1.78;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Subtle grain texture overlay */
body::before {
  content: "";
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  opacity: 0.025;
  pointer-events: none;
  z-index: 9999;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  background-repeat: repeat;
  background-size: 256px 256px;
}

/* --- Reading progress bar --- */
.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--bronze), var(--cinnabar));
  z-index: 10000;
  width: 0%;
  transition: width 0.1s linear;
}

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.15;
  color: var(--ink-deep);
}

h2 {
  font-size: 1.6rem;
  margin-top: var(--space-xl);
  margin-bottom: var(--space-md);
}

h3 {
  font-size: 1.2rem;
  margin-top: var(--space-lg);
  margin-bottom: var(--space-sm);
}

p {
  margin-bottom: var(--space-md);
}

/* --- Chinese text --- */
.zh {
  font-family: var(--font-chinese);
  color: var(--ink-deep);
  line-height: 2.0;
}

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

a:hover {
  color: var(--cinnabar-dark);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}

a:visited {
  color: var(--cinnabar);
}

/* ==========================================================================
   SITE HEADER — Dark inkstone band
   ========================================================================== */
.site-header {
  background: var(--stone);
  padding: var(--space-xl) var(--space-lg) var(--space-lg);
  margin-bottom: 0;
  text-align: center;
}

.site-header a {
  color: inherit;
  text-decoration: none;
}

.site-header a:hover {
  text-decoration: none;
}

.site-title {
  font-family: var(--font-display);
  font-size: 1.8rem;
  font-weight: 300;
  letter-spacing: 0.2em;
  color: var(--paper);
}

.site-title .zh {
  font-family: var(--font-chinese);
  font-size: clamp(3.5rem, 8vw, 5.5rem);
  font-weight: 400;
  color: #fff;
  display: block;
  margin-bottom: var(--space-sm);
  letter-spacing: 0.3em;
  line-height: 1;
}

.site-subtitle {
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-style: italic;
  color: var(--paper-edge);
  font-weight: 400;
  margin-top: var(--space-md);
  letter-spacing: 0.02em;
}

.site-attribution {
  font-family: var(--font-ui);
  font-size: 0.8rem;
  color: var(--ink-ghost);
  letter-spacing: 0.04em;
  margin-top: var(--space-sm);
}

.site-nav {
  margin-top: var(--space-lg);
  font-family: var(--font-ui);
  font-size: 0.8rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.site-nav a {
  margin: 0 var(--space-md);
  color: var(--paper-edge);
  transition: color 0.2s ease;
}

.site-nav a:hover {
  color: var(--bronze-light);
  text-decoration: none;
}

/* Gold accent line under header */
.site-header::after {
  content: "";
  display: block;
  width: 60px;
  height: 2px;
  background: var(--bronze);
  margin: var(--space-lg) auto 0;
}

/* --- Chapter-page header (compact) --- */
.site-header.compact {
  padding: var(--space-md) var(--space-lg);
  text-align: left;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-header.compact .site-title {
  font-size: 1.1rem;
  letter-spacing: 0.15em;
}

.site-header.compact .site-title .zh {
  font-size: 1.5rem;
  display: inline;
  margin-bottom: 0;
  margin-right: var(--space-xs);
  letter-spacing: 0.1em;
}

.site-header.compact::after {
  display: none;
}

.site-header.compact .site-nav {
  margin-top: 0;
}

/* ==========================================================================
   MAIN CONTENT AREA
   ========================================================================== */
main, article {
  max-width: var(--measure);
  margin: 0 auto;
  padding: var(--space-xl) var(--space-lg) var(--space-2xl);
}

/* ==========================================================================
   TABLE OF CONTENTS
   ========================================================================== */
.toc-part {
  margin-bottom: var(--space-2xl);
}

.toc-part-heading {
  font-family: var(--font-ui);
  font-size: 0.78rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--bronze);
  padding-bottom: var(--space-sm);
  margin-bottom: var(--space-md);
  border-bottom: 1px solid var(--ink-ghost);
  font-weight: 600;
}

.toc-part-heading .zh {
  text-transform: none;
  letter-spacing: 0.05em;
  font-size: 0.9rem;
  margin-left: var(--space-sm);
  color: var(--ink-light);
  font-weight: 400;
}

.toc-list {
  list-style: none;
}

.toc-item {
  padding: 0.65rem 0.5rem;
  border-bottom: 1px solid var(--paper-edge);
  display: flex;
  align-items: baseline;
  gap: var(--space-md);
  transition: background-color 0.15s ease;
  border-radius: 2px;
}

.toc-item:hover {
  background-color: var(--paper-tint);
}

.toc-item:last-child {
  border-bottom: none;
}

.toc-number {
  font-family: var(--font-display);
  font-size: 0.85rem;
  color: var(--bronze);
  min-width: 2rem;
  flex-shrink: 0;
  font-weight: 600;
}

.toc-title-en {
  flex: 1;
  font-family: var(--font-display);
  font-size: 1.05rem;
}

.toc-title-zh {
  font-family: var(--font-chinese);
  font-size: 1.1rem;
  color: var(--ink);
  flex-shrink: 0;
}

/* Lost chapters */
.toc-item.lost {
  color: var(--lost);
}

.toc-item.lost:hover {
  background-color: transparent;
}

.toc-item.lost .toc-title-en,
.toc-item.lost a {
  color: var(--lost);
  pointer-events: none;
  font-style: italic;
}

.toc-item.lost .toc-title-zh {
  color: var(--lost);
}

.toc-item.lost .toc-number {
  color: var(--lost);
}

.toc-lost-label {
  font-family: var(--font-ui);
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--lost);
  margin-left: var(--space-sm);
  font-style: normal;
}

/* ==========================================================================
   CHAPTER PAGE
   ========================================================================== */
.chapter-header {
  padding: var(--space-xl) 0 var(--space-lg);
  margin-bottom: var(--space-md);
  text-align: center;
}

.chapter-number {
  font-family: var(--font-ui);
  font-size: 0.72rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--bronze);
  margin-bottom: var(--space-md);
  font-weight: 600;
}

.chapter-title-zh {
  font-family: var(--font-chinese);
  font-size: clamp(2.8rem, 6vw, 4rem);
  font-weight: 400;
  color: var(--ink-deep);
  margin-bottom: var(--space-sm);
  line-height: 1.1;
  letter-spacing: 0.15em;
}

.chapter-title {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3vw, 2.4rem);
  font-weight: 300;
  font-style: italic;
  color: var(--ink);
  letter-spacing: 0.02em;
}

/* Gold rule after chapter header */
.chapter-header::after {
  content: "";
  display: block;
  width: 40px;
  height: 2px;
  background: var(--bronze);
  margin: var(--space-xl) auto 0;
}

/* ==========================================================================
   LANGUAGE TOGGLE
   ========================================================================== */
.lang-toggle {
  font-family: var(--font-ui);
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-xl);
  display: flex;
  gap: var(--space-lg);
  justify-content: center;
}

.lang-toggle button {
  font-family: var(--font-ui);
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  padding: var(--space-xs) 0;
  border: none;
  background: transparent;
  color: var(--ink-light);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.lang-toggle button:hover {
  color: var(--ink);
}

.lang-toggle button.active {
  color: var(--ink);
  border-bottom-color: var(--bronze);
}

/* ==========================================================================
   BILINGUAL TEXT — Row-paired layout
   Each paragraph pair sits side by side in its own row.
   ========================================================================== */
.bilingual {
  max-width: var(--measure);
  margin: 0 auto var(--space-lg);
}

/* Each para-pair is a row with zh + en side by side */
.para-pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  align-items: start;
}

.para-pair .para-zh {
  padding-right: var(--space-xl);
  border-right: 1px solid var(--ink-ghost);
}

.para-pair .para-en {
  padding-left: var(--space-xl);
}

/* Drop cap for first English paragraph */
.para-pair:first-child .para-en p::first-letter {
  font-family: var(--font-display);
  font-size: 3.2rem;
  float: left;
  line-height: 0.8;
  padding-right: 0.12em;
  padding-top: 0.08em;
  color: var(--cinnabar);
  font-weight: 700;
}

/* Chinese-only para-pairs (no .para-en) */
.para-pair:not(:has(.para-en)) {
  grid-template-columns: 1fr;
  max-width: var(--reading-measure);
  margin-left: auto;
  margin-right: auto;
}

.para-pair:not(:has(.para-en)) .para-zh {
  border-right: none;
  padding-right: 0;
}

/* ---- Legacy column layout (Chinese-only chapters still use col-zh) ---- */
.bilingual .col-zh {
  max-width: var(--reading-measure);
  margin: 0 auto;
}

/* Language visibility — "Both" is default (no body class) */
body.lang-en .para-zh { display: none; }
body.lang-en .para-pair {
  grid-template-columns: 1fr;
  max-width: var(--reading-measure);
  margin-left: auto;
  margin-right: auto;
}
body.lang-en .para-en { padding-left: 0; }

body.lang-zh .para-en { display: none; }
body.lang-zh .para-pair {
  grid-template-columns: 1fr;
  max-width: var(--reading-measure);
  margin-left: auto;
  margin-right: auto;
}
body.lang-zh .para-zh {
  border-right: none;
  padding-right: 0;
}

/* ==========================================================================
   PARAGRAPH PAIRS
   ========================================================================== */
.para-pair {
  margin-bottom: var(--space-xl);
  padding-bottom: var(--space-xl);
  border-bottom: 1px solid var(--paper-edge);
}

.para-pair:last-child {
  border-bottom: none;
}

.para-pair p {
  margin-bottom: 0;
}

/* ==========================================================================
   SCROLL REVEAL
   ========================================================================== */
.para-pair {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.6s cubic-bezier(0.23, 1, 0.32, 1),
              transform 0.6s cubic-bezier(0.23, 1, 0.32, 1);
}

.para-pair.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Disable animations if user prefers reduced motion */
@media (prefers-reduced-motion: reduce) {
  .para-pair {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

/* ==========================================================================
   CHAPTER NAVIGATION
   ========================================================================== */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  padding-top: var(--space-xl);
  margin-top: var(--space-3xl);
  border-top: 1px solid var(--ink-ghost);
  font-family: var(--font-display);
  gap: var(--space-lg);
}

.chapter-nav a {
  color: var(--ink-light);
  font-size: 0.95rem;
  transition: color 0.2s ease;
  max-width: 45%;
}

.chapter-nav a:hover {
  color: var(--cinnabar);
  text-decoration: none;
}

.chapter-nav .next {
  margin-left: auto;
  text-align: right;
}

/* ==========================================================================
   ATTRIBUTION / FOOTER
   ========================================================================== */
.attribution {
  font-family: var(--font-ui);
  font-size: 0.72rem;
  color: var(--ink-light);
  letter-spacing: 0.04em;
  margin-top: var(--space-lg);
}

.site-footer {
  background: var(--stone);
  padding: var(--space-xl) var(--space-lg);
  margin-top: var(--space-3xl);
  font-family: var(--font-ui);
  font-size: 0.78rem;
  color: var(--paper-edge);
  text-align: center;
  letter-spacing: 0.04em;
}

.site-footer a {
  color: var(--paper-tint);
}

.site-footer a:hover {
  color: var(--bronze-light);
}

/* ==========================================================================
   EDITORIAL MARKER
   ========================================================================== */
.editorial {
  font-family: var(--font-ui);
  font-size: 0.65rem;
  color: var(--ink-faint);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-style: italic;
}

/* ==========================================================================
   ABOUT PAGE
   ========================================================================== */
.about-content {
  max-width: var(--reading-measure);
  margin: 0 auto;
}

.about-content p {
  margin-bottom: var(--space-md);
}

.about-content h2 {
  margin-top: var(--space-2xl);
  padding-top: var(--space-xl);
  border-top: 1px solid var(--ink-ghost);
  font-style: italic;
  font-weight: 300;
  font-size: 1.8rem;
}

.about-content h2:first-of-type {
  border-top: none;
  padding-top: 0;
}

.design-principle {
  margin-bottom: var(--space-xl);
}

.design-principle-name {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--ink);
}

.design-principle-name .zh {
  font-weight: 400;
  font-size: 1.2rem;
  color: var(--bronze);
  margin-left: var(--space-xs);
}

.design-principle p {
  color: var(--ink-light);
  font-size: 0.95rem;
}

/* ==========================================================================
   RESPONSIVE
   ========================================================================== */
@media (max-width: 768px) {
  html {
    font-size: 16px;
  }

  .site-header {
    padding: var(--space-2xl) var(--space-md) var(--space-lg);
  }

  .site-header.compact {
    padding: var(--space-md);
  }

  main, article {
    padding: var(--space-lg) var(--space-md);
  }

  .para-pair {
    grid-template-columns: 1fr;
  }

  .para-pair .para-zh {
    border-right: none;
    padding-right: 0;
    padding-bottom: var(--space-md);
    border-bottom: 1px solid var(--ink-ghost);
    margin-bottom: var(--space-md);
  }

  .para-pair .para-en {
    padding-left: 0;
  }

  .toc-item {
    flex-wrap: wrap;
    gap: var(--space-xs);
  }

  .toc-title-zh {
    width: 100%;
    margin-left: calc(2rem + var(--space-md));
    font-size: 1rem;
  }

  .chapter-title-zh {
    letter-spacing: 0.08em;
  }
}

@media (max-width: 480px) {
  .chapter-nav {
    flex-direction: column;
    gap: var(--space-md);
  }

  .chapter-nav a {
    max-width: 100%;
  }

  .chapter-nav .next {
    margin-left: 0;
    text-align: left;
  }

  .lang-toggle {
    gap: var(--space-md);
  }

  .site-nav a {
    margin: 0 var(--space-sm);
    font-size: 0.7rem;
  }
}