:root {
  color-scheme: light;
  --bg: #f7f7f4;
  --panel: #ffffff;
  --text: #202124;
  --muted: #62666d;
  --border: #d9d9d2;
  --code-bg: #16181d;
  --code-text: #f3f5f7;
  --accent: #1f6f68;
  --accent-2: #8a4b12;
  --blue: #245c9c;
  --green: #2e6f4e;
  --red: #a13d3d;
  --yellow: #7a5b00;
  --shadow: 0 10px 24px rgba(32, 33, 36, 0.08);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.7;
}

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

.site-header {
  border-bottom: 1px solid var(--border);
  background: var(--panel);
}

.site-header-inner {
  max-width: 1180px;
  margin: 0 auto;
  padding: 28px 24px;
}

.site-title,
.chapter-title {
  margin: 0;
  letter-spacing: 0;
  line-height: 1.2;
}

.site-title {
  font-size: clamp(28px, 4vw, 44px);
}

.chapter-title {
  font-size: clamp(26px, 4vw, 40px);
}

.site-subtitle,
.chapter-subtitle {
  max-width: 820px;
  margin: 12px 0 0;
  color: var(--muted);
}

.chapter-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 18px;
}

.badge {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 4px 10px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: #fafafa;
  color: var(--muted);
  font-size: 14px;
}

.layout {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  gap: 28px;
  max-width: 1180px;
  margin: 0 auto;
  padding: 28px 24px 56px;
}

.toc {
  position: sticky;
  top: 16px;
  align-self: start;
  max-height: calc(100vh - 32px);
  overflow: auto;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
}

.toc h2 {
  margin: 0 0 10px;
  font-size: 16px;
}

.toc ol,
.toc ul {
  margin: 0;
  padding-left: 20px;
}

.toc li {
  margin: 7px 0;
}

.content {
  min-width: 0;
}

.section {
  margin: 0 0 28px;
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
  box-shadow: var(--shadow);
}

.section h2 {
  margin-top: 0;
  line-height: 1.3;
}

.section h3 {
  margin-top: 24px;
  line-height: 1.35;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 16px;
}

.chapter-card {
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
}

.chapter-card.pending {
  background: #fbfbf9;
  color: var(--muted);
}

.chapter-card h3 {
  margin: 0 0 8px;
}

.chapter-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 12px;
}

.chapter-links .disabled-link {
  color: var(--muted);
  text-decoration: none;
}

.route-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 14px;
}

.route-card {
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fbfbf9;
}

.route-card h3 {
  margin-top: 0;
}

.summary-card,
.java-card,
.source-card,
.feynman-card,
.exercise-card,
.warning-card,
.next-card {
  margin: 18px 0;
  padding: 16px 18px;
  border: 1px solid var(--border);
  border-left: 5px solid var(--accent);
  border-radius: 8px;
  background: #fbfbf9;
}

.summary-card {
  border-left-color: var(--accent);
}

.java-card {
  border-left-color: var(--blue);
}

.source-card {
  border-left-color: var(--accent-2);
}

.feynman-card {
  border-left-color: var(--green);
}

.exercise-card {
  border-left-color: #5a4fb0;
}

.warning-card {
  border-left-color: var(--red);
}

.next-card {
  border-left-color: var(--yellow);
}

.card-title {
  margin: 0 0 8px;
  font-weight: 700;
}

code {
  padding: 0.12em 0.28em;
  border-radius: 4px;
  background: #ecece6;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.94em;
}

pre {
  overflow: auto;
  margin: 16px 0;
  padding: 16px;
  border-radius: 8px;
  background: var(--code-bg);
  color: var(--code-text);
  line-height: 1.55;
}

pre code {
  padding: 0;
  background: transparent;
  color: inherit;
  font-size: 14px;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
}

th,
td {
  padding: 10px 12px;
  border: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}

th {
  background: #eeeeea;
}

.footer-nav {
  margin-top: 32px;
  padding-top: 18px;
  border-top: 1px solid var(--border);
}

@media (max-width: 860px) {
  .layout {
    display: block;
    padding: 18px 16px 42px;
  }

  .toc {
    position: static;
    max-height: none;
    margin-bottom: 18px;
  }

  .site-header-inner {
    padding: 24px 16px;
  }

  .section {
    padding: 18px;
  }
}