/* =========================================================================
   分布式系统寓言集 · Parables of Distributed Systems
   A literary-scholarly stylesheet. Paper and ink; one vermilion seal.
   ========================================================================= */

/* ---------- Tokens ---------- */

:root {
  /* Paper & ink */
  --paper:          #F7F3EB;   /* warm off-white, aged xuan paper */
  --paper-deep:     #EFE9DC;   /* slightly deeper for cards/hover */
  --ink:            #1A1612;   /* near-black with warm undertone */
  --ink-2:          #5C574E;   /* secondary text */
  --ink-3:          #938C7E;   /* tertiary / meta */
  --rule:           #DDD5C5;   /* hairline rules */
  --rule-soft:      #E8E1D1;

  /* The one accent — a deep seal vermilion */
  --seal:           #9A2B1F;
  --seal-deep:      #7A1F14;
  --seal-soft:      rgba(154, 43, 31, 0.06);
  --seal-softer:    rgba(154, 43, 31, 0.03);

  /* Typography */
  --font-zh-serif:
    "Songti SC", "SongtiSC",
    "Source Han Serif SC", "Source Han Serif CN",
    "Noto Serif CJK SC", "Noto Serif SC",
    "STSong", "STSongti-SC-Regular",
    "SimSun", serif;

  --font-en-serif:
    "Cormorant Garamond",
    "EB Garamond", "Garamond",
    Georgia, Cambria, "Times New Roman", serif;

  --font-mono:
    "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  /* Rhythm */
  --measure:        42rem;     /* reading column (~672px) */
  --measure-wide:   48rem;
  --stack:          1.85;      /* line-height for Chinese body */
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper:       #15120D;
    --paper-deep:  #1D1913;
    --ink:         #E8DFD0;
    --ink-2:       #9E958A;
    --ink-3:       #6C665A;
    --rule:        #2D2821;
    --rule-soft:   #221E18;
    --seal:        #C0554A;
    --seal-deep:   #E16B5E;
    --seal-soft:   rgba(192, 85, 74, 0.10);
    --seal-softer: rgba(192, 85, 74, 0.05);
  }
}

/* ---------- Reset / base ---------- */

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

html {
  -webkit-text-size-adjust: 100%;
  -moz-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-zh-serif);
  font-size: 17px;
  line-height: var(--stack);
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: "palt" 1;  /* proportional kana/Latin metrics */
  text-rendering: optimizeLegibility;
  min-height: 100vh;
  /* Subtle paper grain — SVG noise, very faint */
  background-image:
    url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='180' height='180'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' seed='3'/><feColorMatrix values='0 0 0 0 0.1 0 0 0 0 0.09 0 0 0 0 0.07 0 0 0 0.035 0'/></filter><rect width='100%25' height='100%25' filter='url(%23n)'/></svg>");
  background-size: 180px 180px;
}

@media (prefers-color-scheme: dark) {
  body {
    background-image:
      url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='180' height='180'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' seed='3'/><feColorMatrix values='0 0 0 0 0.9 0 0 0 0 0.87 0 0 0 0 0.8 0 0 0 0.02 0'/></filter><rect width='100%25' height='100%25' filter='url(%23n)'/></svg>");
  }
}

@media (min-width: 900px) {
  body { font-size: 18px; }
}

::selection {
  background: var(--seal);
  color: var(--paper);
}

a {
  color: inherit;
  text-decoration: none;
  transition: color 180ms ease;
}

a:hover { color: var(--seal); }

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

/* ---------- Layout containers ---------- */

.shell {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 0 1.4rem;
}

.shell--wide { max-width: var(--measure-wide); }

/* ---------- Top bar (tiny, sits above content) ---------- */

.topbar {
  padding: 1.6rem 1.4rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-en-serif);
  font-size: 0.82rem;
  color: var(--ink-3);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-variant: small-caps;
}

.topbar-left { display: flex; align-items: center; gap: 0.8rem; }

.seal-chip {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  background: var(--seal);
  color: var(--paper);
  font-family: var(--font-zh-serif);
  font-size: 14px;
  line-height: 1;
  letter-spacing: 0;
  text-transform: none;
  font-variant: normal;
  border-radius: 1px;
  box-shadow: 0 1px 0 rgba(0,0,0,0.04);
  transform: rotate(-2deg);
  transition: transform 400ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

a:hover .seal-chip { transform: rotate(2deg); }

.topbar a:hover { color: var(--ink); }

/* ================================================================
   INDEX PAGE
   ================================================================ */

/* ---------- Hero ---------- */

.hero {
  padding: 5rem 0 3.5rem;
  text-align: center;
  position: relative;
}

@media (min-width: 900px) {
  .hero { padding: 7rem 0 4.5rem; }
}

.hero-title {
  font-family: var(--font-zh-serif);
  font-weight: 500;
  font-size: clamp(2.2rem, 5.5vw, 3.6rem);
  line-height: 1.2;
  letter-spacing: 0.2em;
  margin: 0 0 1.2rem;
  color: var(--ink);
  /* fade-rise on load */
  animation: rise 900ms cubic-bezier(0.2, 0.8, 0.2, 1) both;
}

.hero-subtitle {
  font-family: var(--font-en-serif);
  font-weight: 400;
  font-style: italic;
  font-size: clamp(1.1rem, 2.2vw, 1.35rem);
  letter-spacing: 0.04em;
  color: var(--ink-2);
  margin: 0 0 2.4rem;
  animation: rise 900ms 120ms cubic-bezier(0.2, 0.8, 0.2, 1) both;
}

.hero-desc {
  max-width: 32rem;
  margin: 0 auto;
  color: var(--ink-2);
  font-size: 0.98rem;
  line-height: 1.95;
  animation: rise 900ms 220ms cubic-bezier(0.2, 0.8, 0.2, 1) both;
}

/* Asterism — one moment of ornament */

.asterism {
  display: block;
  text-align: center;
  color: var(--seal);
  font-family: var(--font-en-serif);
  font-size: 1.1rem;
  letter-spacing: 1em;           /* space out the three dots */
  padding-left: 1em;             /* offset for balance */
  line-height: 1;
  margin: 3.2rem auto;
  opacity: 0.85;
  user-select: none;
}

.asterism::before { content: "⁂"; }

/* ---------- Volume separator ---------- */

.volume-head {
  display: flex;
  align-items: baseline;
  gap: 1.2rem;
  margin: 4.2rem 0 2.4rem;
  padding-top: 0.4rem;
}

.volume-head::before {
  content: "";
  flex: 0 0 1.2rem;
  border-top: 1px solid var(--rule);
  margin-top: 0.7em;
}

.volume-head::after {
  content: "";
  flex: 1 1 auto;
  border-top: 1px solid var(--rule);
  margin-top: 0.7em;
}

.volume-zh {
  font-family: var(--font-zh-serif);
  font-weight: 500;
  font-size: 1.1rem;
  letter-spacing: 0.3em;
  color: var(--ink);
  margin: 0;
}

.volume-en {
  font-family: var(--font-en-serif);
  font-style: italic;
  font-size: 0.85rem;
  letter-spacing: 0.15em;
  color: var(--ink-3);
  text-transform: lowercase;
  font-variant: small-caps;
}

.volume-note {
  font-family: var(--font-zh-serif);
  font-size: 0.86rem;
  color: var(--ink-3);
  margin: 0 0 2.8rem;
  text-align: center;
  letter-spacing: 0.04em;
  font-style: normal;
}

/* ---------- Table of Contents entries ---------- */

.toc { margin: 0; padding: 0; list-style: none; }

.toc-entry {
  position: relative;
  display: grid;
  grid-template-columns: 3rem 1fr;
  gap: 1.2rem 1.4rem;
  padding: 1.6rem 1rem 1.7rem;
  margin: 0 -1rem;
  border-radius: 2px;
  border-bottom: 1px solid var(--rule-soft);
  color: inherit;
  transition:
    background 220ms ease,
    transform 280ms cubic-bezier(0.2, 0.8, 0.2, 1);
  /* stagger-in animation, driven by --i custom prop from JS */
  animation: rise 700ms cubic-bezier(0.2, 0.8, 0.2, 1) both;
  animation-delay: calc(280ms + var(--i, 0) * 45ms);
}

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

.toc-entry:hover {
  background: var(--seal-softer);
}

.toc-entry:hover .toc-title { color: var(--seal); }

.toc-entry:hover .toc-number {
  color: var(--seal-deep);
  transform: translateX(-2px);
}

@media (min-width: 720px) {
  .toc-entry {
    grid-template-columns: 4rem 1fr auto;
    gap: 0.8rem 2.2rem;
    padding: 2rem 1rem 2.1rem;
  }
}

.toc-number {
  font-family: var(--font-zh-serif);
  font-weight: 500;
  font-size: 1.8rem;
  line-height: 1;
  color: var(--seal);
  letter-spacing: 0;
  padding-top: 0.1em;
  transition: transform 280ms cubic-bezier(0.2, 0.8, 0.2, 1),
              color 220ms ease;
  font-variant-numeric: lining-nums;
  /* Traditional vertical emphasis */
  writing-mode: horizontal-tb;
}

.toc-body { min-width: 0; }

.toc-title {
  font-family: var(--font-zh-serif);
  font-weight: 500;
  font-size: 1.4rem;
  line-height: 1.35;
  letter-spacing: 0.08em;
  color: var(--ink);
  margin: 0 0 0.55rem;
  transition: color 220ms ease;
}

@media (min-width: 720px) {
  .toc-title { font-size: 1.55rem; }
}

.toc-concept {
  font-size: 0.92rem;
  color: var(--ink-2);
  margin: 0 0 0.65rem;
  line-height: 1.5;
  letter-spacing: 0.02em;
}

.toc-concept-en {
  font-family: var(--font-en-serif);
  font-style: italic;
  color: var(--ink-3);
  font-size: 0.88rem;
  letter-spacing: 0.01em;
  margin-left: 0.25rem;
}

.toc-concept-en::before {
  content: "·";
  margin-right: 0.45em;
  color: var(--ink-3);
  font-style: normal;
}

.toc-excerpt {
  font-family: var(--font-zh-serif);
  font-size: 0.9rem;
  line-height: 1.75;
  color: var(--ink-2);
  margin: 0;
  letter-spacing: 0.02em;
  /* Use a leading quote mark in vermilion for character */
  position: relative;
  padding-left: 0.85rem;
  border-left: 1px solid var(--rule);
}

.toc-meta {
  grid-column: 2;
  font-family: var(--font-en-serif);
  font-variant: small-caps;
  font-size: 0.78rem;
  letter-spacing: 0.12em;
  color: var(--ink-3);
  padding-top: 0.35rem;
}

@media (min-width: 720px) {
  .toc-meta {
    grid-column: 3;
    grid-row: 1;
    padding-top: 0.65rem;
    white-space: nowrap;
    align-self: start;
  }
}

/* ---------- Site footer ---------- */

.site-foot {
  margin: 5rem 0 3.5rem;
  padding-top: 2.2rem;
  border-top: 1px solid var(--rule-soft);
  text-align: center;
  font-size: 0.82rem;
  color: var(--ink-3);
  font-family: var(--font-en-serif);
  font-style: italic;
  letter-spacing: 0.04em;
}

.site-foot a { border-bottom: 1px solid var(--rule); }
.site-foot a:hover { border-bottom-color: var(--seal); }

/* ================================================================
   ARTICLE PAGE
   ================================================================ */

.article {
  padding: 1.5rem 0 5rem;
  animation: rise 700ms 80ms cubic-bezier(0.2, 0.8, 0.2, 1) both;
}

/* Back navigation */
.article-back {
  margin: 0 0 4rem;
  font-family: var(--font-en-serif);
  font-variant: small-caps;
  font-size: 0.85rem;
  letter-spacing: 0.1em;
  color: var(--ink-3);
}

.article-back a {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.article-back a::before {
  content: "←";
  display: inline-block;
  transition: transform 220ms ease;
  font-variant: normal;
  font-style: normal;
}

.article-back a:hover::before { transform: translateX(-4px); }

/* Header */

.article-head {
  text-align: center;
  margin: 0 0 3.4rem;
}

.article-number {
  font-family: var(--font-zh-serif);
  font-size: 2.6rem;
  font-weight: 400;
  color: var(--seal);
  line-height: 1;
  margin: 0 0 1.1rem;
  letter-spacing: 0.05em;
}

.article-title {
  font-family: var(--font-zh-serif);
  font-weight: 500;
  font-size: clamp(2rem, 4.5vw, 2.7rem);
  line-height: 1.25;
  letter-spacing: 0.15em;
  color: var(--ink);
  margin: 0 0 1.4rem;
  padding-left: 0.15em;            /* compensate trailing letter-spacing */
}

.article-concept {
  font-family: var(--font-zh-serif);
  font-size: 1.05rem;
  color: var(--ink-2);
  margin: 0 0 0.35rem;
  letter-spacing: 0.08em;
}

.article-concept-en {
  font-family: var(--font-en-serif);
  font-style: italic;
  font-size: 0.98rem;
  color: var(--ink-3);
  margin: 0 0 1.6rem;
  letter-spacing: 0.02em;
}

.article-meta {
  font-family: var(--font-en-serif);
  font-variant: small-caps;
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  color: var(--ink-3);
}

.article-meta::before,
.article-meta::after {
  content: "";
  display: inline-block;
  width: 1.6rem;
  height: 1px;
  background: var(--rule);
  vertical-align: middle;
  margin: 0 0.9rem;
}

/* Body — generous reading typography */

.article-body {
  font-family: var(--font-zh-serif);
  font-size: 1.02rem;
  line-height: var(--stack);
  color: var(--ink);
  letter-spacing: 0.015em;
}

@media (min-width: 900px) {
  .article-body { font-size: 1.08rem; }
}

.article-body > *:first-child { margin-top: 0; }
.article-body > *:last-child  { margin-bottom: 0; }

/* Suppress the h1 title that the md file already contains (we render our own) */
.article-body > h1:first-child,
.article-body > h1:first-child + p:has(strong):not(:has(em)) {
  display: none;
}

/* Actually, h1 hiding is fragile. Better: use JS to strip title on load. */

.article-body p {
  margin: 0 0 1.3em;
}

/* Section headings within body — 故事 / 概念解析 */
.article-body h2,
.article-body h3 {
  font-family: var(--font-zh-serif);
  font-weight: 500;
  letter-spacing: 0.2em;
  color: var(--ink);
  position: relative;
  text-align: center;
  margin: 3.5em 0 2em;
}

.article-body h2 {
  font-size: 1.2rem;
  padding-top: 1em;
}

.article-body h3 {
  font-size: 1.05rem;
}

/* Small asterism above section headings */
.article-body h2::before,
.article-body h3::before {
  content: "⁂";
  display: block;
  color: var(--seal);
  font-family: var(--font-en-serif);
  font-size: 1rem;
  letter-spacing: 0.7em;
  padding-left: 0.7em;
  margin-bottom: 1.3em;
  opacity: 0.8;
}

/* The very first h3 sits closer to the header */
.article-body h3:first-of-type { margin-top: 2em; }

/* Bold emphasis */
.article-body strong {
  font-weight: 600;
  color: var(--ink);
  /* slight weight bump looks terrible in some CJK fonts — prefer color */
}

.article-body em {
  font-style: italic;
  color: var(--ink);
}

.article-body em:lang(en) {
  font-family: var(--font-en-serif);
}

/* Horizontal rules → asterism */
.article-body hr {
  border: none;
  height: 1.5em;
  margin: 3em 0;
  text-align: center;
  overflow: visible;
}

.article-body hr::after {
  content: "⁂";
  display: inline-block;
  color: var(--seal);
  font-family: var(--font-en-serif);
  letter-spacing: 0.7em;
  padding-left: 0.7em;
  font-size: 1rem;
  opacity: 0.8;
}

/* Blockquotes — the story's reveal lines */
.article-body blockquote {
  margin: 2.2em 0;
  padding: 0.2em 0 0.2em 1.6em;
  border-left: 2px solid var(--seal);
  color: var(--ink-2);
  font-style: italic;
  font-size: 1.02em;
}

.article-body blockquote p {
  margin: 0 0 0.9em;
}

.article-body blockquote p:last-child { margin-bottom: 0; }

/* Lists */
.article-body ul,
.article-body ol {
  margin: 1.2em 0;
  padding-left: 1.8em;
}

.article-body li {
  margin-bottom: 0.8em;
  line-height: var(--stack);
}

.article-body li::marker {
  color: var(--ink-3);
}

.article-body ol > li::marker {
  font-family: var(--font-en-serif);
  font-weight: 500;
}

/* Code (rare in these articles, but style them anyway) */
.article-body code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--seal-softer);
  padding: 0.1em 0.4em;
  border-radius: 2px;
  color: var(--seal-deep);
}

.article-body pre {
  background: var(--paper-deep);
  border-left: 2px solid var(--rule);
  padding: 1rem 1.2rem;
  overflow-x: auto;
  font-size: 0.85em;
  line-height: 1.7;
  margin: 1.5em 0;
}

.article-body pre code {
  background: none;
  padding: 0;
  color: var(--ink);
}

/* Tables — in case any article uses one */
.article-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 2em 0;
  font-size: 0.92em;
}

.article-body th,
.article-body td {
  padding: 0.75em 0.8em;
  border-bottom: 1px solid var(--rule-soft);
  text-align: left;
  vertical-align: top;
}

.article-body th {
  font-weight: 500;
  border-bottom-color: var(--rule);
  color: var(--ink);
  letter-spacing: 0.04em;
}

/* ---------- Article footer nav ---------- */

.article-nav {
  margin: 5rem 0 0;
  padding-top: 3rem;
  border-top: 1px solid var(--rule-soft);
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1.5rem;
  align-items: stretch;
}

.article-nav-link {
  display: block;
  padding: 1rem 0;
  font-family: var(--font-zh-serif);
  transition: color 220ms ease;
}

.article-nav-link--prev { text-align: left; }
.article-nav-link--next { text-align: right; }

.article-nav-link .label {
  display: block;
  font-family: var(--font-en-serif);
  font-variant: small-caps;
  font-size: 0.76rem;
  letter-spacing: 0.15em;
  color: var(--ink-3);
  margin-bottom: 0.4em;
}

.article-nav-link .title {
  font-size: 1.05rem;
  color: var(--ink);
  letter-spacing: 0.1em;
}

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

.article-nav-home {
  align-self: center;
  padding: 1rem 0.8rem;
  font-family: var(--font-en-serif);
  font-variant: small-caps;
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  color: var(--ink-3);
  text-align: center;
  border-left: 1px solid var(--rule-soft);
  border-right: 1px solid var(--rule-soft);
}

.article-nav-home:hover { color: var(--seal); }

.article-nav-link[aria-disabled="true"] {
  opacity: 0.35;
  pointer-events: none;
}

.article-nav-link--prev .title::before {
  content: "← ";
  display: inline-block;
  margin-right: 0.2em;
  transition: transform 220ms ease;
}

.article-nav-link--next .title::after {
  content: " →";
  display: inline-block;
  margin-left: 0.2em;
  transition: transform 220ms ease;
}

.article-nav-link--prev:hover .title::before { transform: translateX(-3px); }
.article-nav-link--next:hover .title::after  { transform: translateX(3px); }

@media (max-width: 640px) {
  .article-nav {
    grid-template-columns: 1fr;
    gap: 0.2rem;
  }
  .article-nav-link--prev,
  .article-nav-link--next { text-align: left; }
  .article-nav-home {
    border-left: none;
    border-right: none;
    border-top: 1px solid var(--rule-soft);
    border-bottom: 1px solid var(--rule-soft);
    padding: 1rem 0;
    margin: 0.4rem 0;
  }
}

/* ---------- Loading / error states ---------- */

.loading {
  text-align: center;
  padding: 5rem 0;
  color: var(--ink-3);
  font-family: var(--font-en-serif);
  font-style: italic;
  letter-spacing: 0.04em;
}

.error {
  text-align: center;
  padding: 5rem 0;
  color: var(--seal-deep);
  font-family: var(--font-zh-serif);
}

/* ---------- Animations ---------- */

@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0ms !important;
    animation-delay: 0ms !important;
    transition-duration: 0ms !important;
  }
}

/* ---------- Focus states (a11y) ---------- */

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

.toc-entry:focus-visible {
  outline-offset: 1px;
  background: var(--seal-soft);
}

/* ---------- Print ---------- */

@media print {
  body { background: white; color: black; }
  .topbar, .article-back, .article-nav, .site-foot { display: none; }
  .article-body { font-size: 11pt; }
}