/* ============================================================
   Infra Learning Path — visual system
   ============================================================ */

:root {
  --bg: #fdfcf8;
  --bg-soft: #f7f5ee;
  --bg-code: #f4f1e8;
  --fg: #1c1917;
  --fg-soft: #57534e;
  --fg-muted: #78716c;
  --border: #e7e5e4;
  --border-strong: #d6d3d1;
  --accent: #c2410c;
  --accent-soft: #fed7aa;
  --accent-bg: #fff7ed;
  --green: #166534;
  --green-bg: #f0fdf4;
  --blue: #1e40af;
  --blue-bg: #eff6ff;
  --yellow-bg: #fefce8;
  --yellow-border: #facc15;
  --red: #991b1b;
  --red-bg: #fef2f2;

  --font-sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto,
    "Helvetica Neue", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, "Cascadia Mono", "JetBrains Mono",
    Consolas, monospace;
  --font-serif: "Source Serif Pro", "Iowan Old Style", Charter, Georgia, serif;

  --radius: 6px;
  --radius-lg: 10px;
  --shadow-sm: 0 1px 2px rgba(28, 25, 23, 0.04);
  --shadow: 0 4px 12px rgba(28, 25, 23, 0.06);

  --content-w: 740px;
  --sidebar-w: 280px;
}

@media (prefers-color-scheme: dark) {
  :root.auto {
    --bg: #1c1917;
    --bg-soft: #292524;
    --bg-code: #292524;
    --fg: #f5f5f4;
    --fg-soft: #d6d3d1;
    --fg-muted: #a8a29e;
    --border: #44403c;
    --border-strong: #57534e;
    --accent: #fb923c;
    --accent-soft: #7c2d12;
    --accent-bg: #292524;
    --green: #4ade80;
    --green-bg: #052e16;
    --blue: #60a5fa;
    --blue-bg: #172554;
    --yellow-bg: #422006;
    --yellow-border: #ca8a04;
    --red: #f87171;
    --red-bg: #450a0a;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.65;
  color: var(--fg);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* ===== Layout ===== */

.layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  min-height: 100vh;
}

.sidebar {
  background: var(--bg-soft);
  border-right: 1px solid var(--border);
  padding: 28px 22px 40px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  font-size: 14px;
}

.sidebar .brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  font-size: 15px;
  color: var(--fg);
  text-decoration: none;
  margin-bottom: 4px;
}

.sidebar .brand .dot {
  width: 10px;
  height: 10px;
  border-radius: 2px;
  background: var(--accent);
  transform: rotate(45deg);
}

.sidebar .tagline {
  color: var(--fg-muted);
  font-size: 12px;
  margin-bottom: 28px;
  line-height: 1.5;
}

.sidebar .nav-group {
  margin-bottom: 22px;
}

.sidebar .nav-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fg-muted);
  font-weight: 600;
  margin-bottom: 8px;
}

.sidebar nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.sidebar nav li {
  margin-bottom: 2px;
}

.sidebar nav a {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 5px 10px;
  border-radius: var(--radius);
  color: var(--fg-soft);
  text-decoration: none;
  border-left: 2px solid transparent;
  margin-left: -2px;
  transition: background 0.12s, color 0.12s;
  line-height: 1.4;
}

.sidebar nav a:hover {
  background: var(--bg);
  color: var(--fg);
}

.sidebar nav a.active {
  color: var(--accent);
  background: var(--accent-bg);
  font-weight: 500;
}

.sidebar nav a .idx {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--fg-muted);
  flex-shrink: 0;
}

.sidebar nav a.active .idx { color: var(--accent); }

.sidebar .foot {
  margin-top: 32px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
  font-size: 12px;
  color: var(--fg-muted);
  line-height: 1.55;
}

.sidebar .foot a { color: var(--fg-muted); text-decoration: underline; }

/* ===== Mobile sidebar ===== */

.menu-btn {
  display: none;
  position: fixed;
  top: 14px;
  left: 14px;
  z-index: 50;
  background: var(--bg);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  padding: 8px 10px;
  cursor: pointer;
  font-size: 14px;
  font-family: var(--font-mono);
}

@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    z-index: 40;
    width: 280px;
    height: 100vh;
    transform: translateX(-100%);
    transition: transform 0.22s ease;
    box-shadow: var(--shadow);
  }
  .sidebar.open { transform: translateX(0); }
  .menu-btn { display: block; }
  .content { padding-top: 60px !important; }
}

/* ===== Content ===== */

.content {
  padding: 64px 56px 96px;
  max-width: calc(var(--content-w) + 112px);
}

.crumbs {
  font-size: 13px;
  color: var(--fg-muted);
  margin-bottom: 18px;
  font-family: var(--font-mono);
}
.crumbs a { color: var(--fg-muted); text-decoration: none; border-bottom: 1px dotted var(--border-strong); }
.crumbs a:hover { color: var(--accent); }
.crumbs .sep { margin: 0 6px; opacity: 0.5; }

.page-title {
  font-size: 36px;
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin: 0 0 6px;
}

.page-sub {
  font-size: 16px;
  color: var(--fg-muted);
  margin: 0 0 36px;
}

.lede {
  font-size: 18px;
  line-height: 1.65;
  color: var(--fg-soft);
  margin: 0 0 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}

h2 {
  font-size: 24px;
  font-weight: 600;
  margin: 56px 0 14px;
  letter-spacing: -0.01em;
  scroll-margin-top: 20px;
}

h2 .num {
  font-family: var(--font-mono);
  color: var(--accent);
  font-weight: 500;
  margin-right: 10px;
  font-size: 18px;
}

h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 36px 0 10px;
  scroll-margin-top: 20px;
}

h4 {
  font-size: 15px;
  font-weight: 600;
  margin: 24px 0 8px;
  color: var(--fg-soft);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

p { margin: 0 0 14px; }

a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid var(--accent-soft);
  transition: border-color 0.12s;
}
a:hover { border-bottom-color: var(--accent); }

ul, ol { padding-left: 22px; margin: 0 0 16px; }
li { margin-bottom: 6px; }
li > ul, li > ol { margin: 6px 0 0; }

hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 48px 0;
}

strong { color: var(--fg); font-weight: 600; }
em { font-style: italic; }

/* ===== Code ===== */

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  padding: 1px 5px;
  background: var(--bg-code);
  border-radius: 4px;
  color: var(--fg);
}

pre {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.55;
  margin: 0 0 18px;
  position: relative;
}
pre code {
  background: transparent;
  padding: 0;
  font-size: inherit;
}

.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--fg-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 3px 8px;
  border-radius: 4px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.15s;
}
pre:hover .copy-btn { opacity: 1; }
.copy-btn:hover { color: var(--accent); }
.copy-btn.copied { color: var(--green); }

/* ===== Callouts ===== */

.callout {
  border-left: 3px solid var(--border-strong);
  background: var(--bg-soft);
  padding: 14px 18px;
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: 18px 0;
}
.callout .label {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fg-muted);
  margin-bottom: 6px;
}
.callout > :last-child { margin-bottom: 0; }

.callout.q { border-color: var(--accent); background: var(--accent-bg); }
.callout.q .label { color: var(--accent); }

.callout.tip { border-color: var(--blue); background: var(--blue-bg); }
.callout.tip .label { color: var(--blue); }

.callout.warn { border-color: var(--yellow-border); background: var(--yellow-bg); }
.callout.warn .label { color: #854d0e; }

.callout.danger { border-color: var(--red); background: var(--red-bg); }
.callout.danger .label { color: var(--red); }

.callout.check { border-color: var(--green); background: var(--green-bg); }
.callout.check .label { color: var(--green); }

/* ===== Code anchor (go-read-this) ===== */

.code-anchor {
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  background: var(--bg);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 14px 18px;
  margin: 18px 0;
  box-shadow: var(--shadow-sm);
}
.code-anchor .label {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}
.code-anchor .label::before {
  content: "→";
  font-family: var(--font-mono);
}
.code-anchor .path {
  font-family: var(--font-mono);
  font-size: 13px;
  background: var(--bg-code);
  padding: 4px 8px;
  border-radius: 4px;
  display: inline-block;
  margin: 4px 4px 4px 0;
  color: var(--fg);
  border: 1px solid var(--border);
}
.code-anchor .path a { border: none; color: inherit; }
.code-anchor .path a:hover { color: var(--accent); }
.code-anchor .ask {
  margin-top: 10px;
  font-size: 14px;
  color: var(--fg-soft);
}
.code-anchor .ask::before {
  content: "带着问题读：";
  font-weight: 600;
  color: var(--accent);
}

/* ===== Predict-then-reveal ===== */

.predict {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin: 20px 0;
  background: var(--bg);
  overflow: hidden;
}
.predict summary {
  cursor: pointer;
  padding: 12px 16px;
  font-weight: 500;
  background: var(--bg-soft);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 10px;
  user-select: none;
}
.predict summary::-webkit-details-marker { display: none; }
.predict summary::before {
  content: "?";
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  background: var(--accent);
  color: white;
  border-radius: 50%;
  font-size: 12px;
  font-weight: 700;
  font-family: var(--font-mono);
  flex-shrink: 0;
}
.predict[open] summary::before {
  content: "✓";
  background: var(--green);
}
.predict summary::after {
  content: "点击展开答案";
  margin-left: auto;
  font-size: 12px;
  color: var(--fg-muted);
  font-weight: 400;
}
.predict[open] summary::after { content: "收起"; }
.predict .body {
  padding: 14px 18px;
  border-top: 1px solid var(--border);
  font-size: 15px;
  line-height: 1.6;
}
.predict .body > :last-child { margin-bottom: 0; }

/* ===== Self-check (checkbox list) ===== */

.selfcheck {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 22px;
  margin: 28px 0;
}
.selfcheck h4 {
  margin-top: 0;
  color: var(--accent);
  display: flex;
  align-items: center;
  gap: 8px;
}
.selfcheck h4::before {
  content: "✓";
  width: 22px;
  height: 22px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--accent);
  color: white;
  border-radius: 50%;
  font-size: 13px;
}
.selfcheck ul { list-style: none; padding: 0; margin: 0; }
.selfcheck li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 8px 0;
  border-bottom: 1px dashed var(--border);
  cursor: pointer;
}
.selfcheck li:last-child { border-bottom: none; }
.selfcheck input[type="checkbox"] {
  margin-top: 4px;
  flex-shrink: 0;
  accent-color: var(--accent);
}
.selfcheck li label { cursor: pointer; flex: 1; font-size: 14px; }
.selfcheck input:checked + label { text-decoration: line-through; color: var(--fg-muted); }

/* ===== Tables ===== */

table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14px;
}
th, td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}
th {
  font-weight: 600;
  color: var(--fg-soft);
  background: var(--bg-soft);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
td code { font-size: 12px; }

/* ===== Timeline ===== */

.timeline {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin: 28px 0;
}
.timeline .step {
  display: grid;
  grid-template-columns: 70px 1fr;
  gap: 16px;
  align-items: flex-start;
  padding: 16px;
  background: var(--bg-soft);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  text-decoration: none;
  color: var(--fg);
  border-bottom: 1px solid var(--border);
  transition: border-color 0.12s, transform 0.12s;
}
.timeline a.step:hover {
  border-color: var(--accent);
  transform: translateY(-1px);
}
.timeline .step .badge {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--accent);
  background: var(--accent-bg);
  border: 1px solid var(--accent-soft);
  padding: 3px 8px;
  border-radius: 4px;
  text-align: center;
  font-weight: 600;
  text-transform: uppercase;
}
.timeline .step .title {
  font-weight: 600;
  font-size: 16px;
  margin: 0 0 4px;
}
.timeline .step .desc {
  font-size: 14px;
  color: var(--fg-muted);
  margin: 0;
  line-height: 1.5;
}

/* ===== Page footer nav ===== */

.pagenav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  margin-top: 64px;
  padding-top: 28px;
  border-top: 1px solid var(--border);
}
.pagenav a {
  display: block;
  padding: 14px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--fg);
  border-bottom: 1px solid var(--border);
  transition: border-color 0.12s;
}
.pagenav a:hover { border-color: var(--accent); }
.pagenav .dir {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fg-muted);
  margin-bottom: 4px;
}
.pagenav .ttl { font-weight: 600; font-size: 15px; }
.pagenav a.next { text-align: right; }
.pagenav a.next .dir::after { content: " →"; }
.pagenav a.prev .dir::before { content: "← "; }
.pagenav .placeholder { visibility: hidden; }

/* ===== Diagram wrappers ===== */

.diagram {
  margin: 24px 0;
  padding: 20px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  text-align: center;
  overflow-x: auto;
}
.diagram svg { max-width: 100%; height: auto; }
.diagram .caption {
  font-size: 13px;
  color: var(--fg-muted);
  margin-top: 12px;
  font-style: italic;
}

/* mermaid container override */
.mermaid {
  background: var(--bg);
  text-align: center;
  margin: 24px 0;
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}

/* ===== Inline tag ===== */

.tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 1px 7px;
  border-radius: 3px;
  background: var(--bg-code);
  color: var(--fg-soft);
  border: 1px solid var(--border);
  margin: 0 2px;
  vertical-align: 1px;
}
.tag.red { color: var(--red); background: var(--red-bg); border-color: var(--red-bg); }
.tag.yellow { color: #854d0e; background: var(--yellow-bg); border-color: var(--yellow-bg); }
.tag.green { color: var(--green); background: var(--green-bg); border-color: var(--green-bg); }
.tag.blue { color: var(--blue); background: var(--blue-bg); border-color: var(--blue-bg); }

/* ===== Landing hero ===== */

.hero {
  padding: 36px 0 24px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 36px;
}
.hero .eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: 14px;
}
.hero h1 {
  font-size: 44px;
  line-height: 1.1;
  letter-spacing: -0.025em;
  margin: 0 0 16px;
  font-weight: 700;
}
.hero .sub {
  font-size: 18px;
  color: var(--fg-soft);
  line-height: 1.55;
  max-width: 600px;
  margin: 0 0 24px;
}
.hero .cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 28px;
}
.btn {
  display: inline-block;
  padding: 10px 18px;
  border-radius: var(--radius);
  font-weight: 500;
  font-size: 14px;
  border: 1px solid var(--border-strong);
  text-decoration: none;
  color: var(--fg);
  background: var(--bg);
  transition: all 0.12s;
  border-bottom: 1px solid var(--border-strong);
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn.primary {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}
.btn.primary:hover { background: #9a3412; border-color: #9a3412; color: white; }

/* ===== Two-col on landing ===== */

.cards-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}
@media (max-width: 720px) {
  .cards-2 { grid-template-columns: 1fr; }
}
.card {
  padding: 18px 20px;
  background: var(--bg-soft);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
}
.card h3 { margin-top: 0; }
.card p { color: var(--fg-soft); font-size: 14px; }

/* ===== KPI strip (landing) ===== */
.kpis {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin: 28px 0;
}
@media (max-width: 720px) { .kpis { grid-template-columns: repeat(2, 1fr); } }
.kpi {
  padding: 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg);
  text-align: center;
}
.kpi .n {
  font-size: 28px;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
  margin-bottom: 6px;
  font-family: var(--font-mono);
}
.kpi .l {
  font-size: 12px;
  color: var(--fg-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* ===== Misc ===== */

.kbd {
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 2px 6px;
  background: var(--bg-soft);
  border: 1px solid var(--border-strong);
  border-bottom-width: 2px;
  border-radius: 4px;
  color: var(--fg);
}

blockquote {
  margin: 18px 0;
  padding: 4px 18px;
  border-left: 3px solid var(--border-strong);
  color: var(--fg-soft);
  font-style: italic;
}

.muted { color: var(--fg-muted); }
.small { font-size: 13px; }

/* file-link styling (links to GitHub source) */
a.file {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--bg-code);
  padding: 1px 6px;
  border-radius: 4px;
  border: 1px solid var(--border);
  color: var(--fg);
}
a.file:hover { color: var(--accent); border-color: var(--accent); }