:root {
  color-scheme: light;
  --ink: #1f2933;
  --muted: #5b6673;
  --line: #d7dde5;
  --paper: #f7f9fb;
  --accent: #0b6b75;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  color: var(--ink);
  background: var(--paper);
  line-height: 1.55;
}

.app-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 250px minmax(0, 1fr);
}

.sidebar {
  background: linear-gradient(180deg, #17213a 0%, #241f56 100%);
  color: #ffffff;
  padding: 22px 14px;
}

.brand {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 22px;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 40px;
  height: 40px;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.12);
  font-weight: 700;
}

.brand h1,
.brand p {
  margin: 0;
}

.brand h1 {
  font-size: 1rem;
}

.brand p {
  color: rgba(255, 255, 255, 0.70);
  font-size: 0.82rem;
}

.nav {
  display: grid;
  gap: 8px;
}

.nav-link {
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr);
  gap: 10px;
  align-items: center;
  min-height: 38px;
  padding: 8px 10px;
  border-radius: 8px;
  color: #ffffff;
  text-decoration: none;
}

.nav-link.active,
.nav-link:hover {
  background: rgba(99, 102, 241, 0.34);
  outline: 1px solid rgba(255, 255, 255, 0.18);
}

.nav-bullet {
  color: rgba(255, 255, 255, 0.78);
  font-size: 0.85rem;
  text-align: center;
}

.nav-label {
  min-width: 0;
  overflow-wrap: anywhere;
}

.content {
  width: min(880px, 100%);
  margin: 0 auto;
  padding: 32px 18px 48px;
}

header {
  border-bottom: 1px solid var(--line);
  padding-bottom: 18px;
  margin-bottom: 22px;
}

h1 {
  margin: 0 0 8px;
  font-size: clamp(2rem, 5vw, 3.25rem);
  line-height: 1.05;
  letter-spacing: 0;
}

h2 {
  margin: 28px 0 10px;
  font-size: 1.25rem;
  letter-spacing: 0;
}

p {
  margin: 0 0 12px;
}

.lead,
.learn-copy {
  color: var(--muted);
  max-width: 720px;
  font-size: 1.05rem;
}

.learn-hero {
  padding: 0;
}

.learn-kicker {
  display: block;
  margin-bottom: 12px;
  color: var(--accent);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

.learn-title {
  color: var(--ink);
}

.formula {
  display: block;
  width: 100%;
  margin: 10px 0 16px;
  padding: 12px 14px;
  border: 1px solid var(--line);
  background: #ffffff;
  font-size: 1rem;
  overflow-x: auto;
  text-align: center;
}

.code-block {
  display: block;
  width: 100%;
  margin: 12px 0 16px;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #101827;
  color: #eef6ff;
  font-family: Consolas, "Courier New", monospace;
  font-size: 0.88rem;
  line-height: 1.45;
  overflow-x: auto;
}

.module-figure {
  margin: 14px 0 18px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
}

.module-figure img {
  display: block;
  width: 100%;
  height: auto;
}

.module-figure figcaption {
  margin-top: 8px;
  color: var(--muted);
  font-size: 0.92rem;
}

.note {
  border-left: 4px solid var(--accent);
  padding: 10px 14px;
  background: #ffffff;
  color: var(--muted);
}

ul {
  margin: 0 0 14px 20px;
  padding: 0;
}

li {
  margin: 6px 0;
}

.axiom-grid {
  display: grid;
  gap: 14px;
  margin-top: 24px;
}

.axiom-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  box-shadow: 0 10px 24px rgba(31, 41, 51, 0.08);
  overflow: hidden;
}

.axiom-card summary {
  display: flex;
  gap: 12px;
  align-items: center;
  min-height: 58px;
  padding: 12px 14px;
  cursor: pointer;
  font-weight: 700;
  list-style: none;
}

.axiom-card summary::-webkit-details-marker {
  display: none;
}

.axiom-card[open] summary {
  border-bottom: 1px solid var(--line);
}

.axiom-card p {
  padding: 0 16px;
}

.axiom-card p:first-of-type {
  padding-top: 14px;
}

.axiom-badge {
  display: inline-grid;
  place-items: center;
  min-width: 44px;
  height: 34px;
  border-radius: 8px;
  background: linear-gradient(135deg, #5b5ff7 0%, #2f6df6 100%);
  color: #ffffff;
  font-weight: 800;
}

.pillar-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-top: 24px;
}

.pillar-card {
  display: grid;
  gap: 10px;
  align-content: start;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  padding: 16px;
  box-shadow: 0 10px 24px rgba(31, 41, 51, 0.08);
}

.pillar-head {
  display: grid;
  grid-template-columns: 56px minmax(0, 1fr);
  gap: 12px;
  align-items: center;
}

.pillar-icon {
  display: grid;
  place-items: center;
  width: 54px;
  height: 54px;
  border-radius: 8px;
  background: linear-gradient(135deg, #5b5ff7 0%, #2f6df6 100%);
  color: #ffffff;
  font-size: 0.82rem;
  font-weight: 800;
}

.pillar-index {
  margin: 0 0 4px;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
}

.pillar-card h2 {
  margin: 0;
}

.pillar-card p {
  margin: 0;
}

.tech-tip {
  margin-top: 4px;
  color: var(--muted);
  font-size: 0.9rem;
}

.pillar-explain {
  margin-top: 30px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}

.pillar-explain h3 {
  margin: 22px 0 8px;
  font-size: 1.08rem;
}

.axiom-explain {
  margin-top: 30px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}

.axiom-explain h3 {
  margin: 22px 0 8px;
  font-size: 1.08rem;
}

.error-code-grid {
  display: grid;
  gap: 12px;
  margin-top: 18px;
}

.error-code-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  padding: 14px 16px;
  box-shadow: 0 8px 18px rgba(31, 41, 51, 0.06);
}

.error-code-card h3 {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: baseline;
  margin: 0 0 8px;
  font-size: 1rem;
}

.error-code-card code {
  border-radius: 6px;
  background: #eef2ff;
  color: #2f44d8;
  padding: 3px 7px;
  font-weight: 800;
}

.error-code-card p {
  margin: 6px 0;
}

@media (max-width: 780px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }

  .pillar-grid {
    grid-template-columns: 1fr;
  }
}

@media print {
  @page {
    size: A4;
    margin: 16mm;
  }

  html,
  body {
    background: #ffffff !important;
    color: #111827 !important;
  }

  .app-shell {
    display: block !important;
    min-height: auto !important;
  }

  .sidebar {
    display: none !important;
  }

  .content,
  .content.learn-content {
    display: block !important;
    width: 100% !important;
    max-width: none !important;
    margin: 0 !important;
    padding: 0 !important;
    background: #ffffff !important;
    color: #111827 !important;
  }

  section,
  .explain-section,
  .formula-block,
  .note,
  .audit-table,
  .code-block {
    box-shadow: none !important;
    break-inside: avoid-page;
    page-break-inside: avoid;
  }

  .format-links {
    display: none !important;
  }
}