/* General look */
.book-html,
.book-body {
  height: 100%;
}

.book-body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Inter", sans-serif;
  background: #faf5ff;
  color: #222;
  user-select: none;
  -webkit-user-select: none;
}

/* Header bar */
.book-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
  padding: 10px 16px;
  background: linear-gradient(to right, #fff7ed, #fce7f3);
  border-bottom: 1px solid #f97316;
}

.book-header-left {
  min-width: 0;
}

.book-title {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 700;
}

.book-subtitle {
  margin: 2px 0 0;
  font-size: 0.85rem;
  color: #6b7280;
}

/* Nav area */
.book-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  align-items: center;
  justify-content: flex-end;
}

.book-home {
  margin-right: 8px;
  padding: 4px 8px;
  border-radius: 999px;
  border: 1px solid #2563eb;
  background: #eff6ff;
  color: #1d4ed8;
  font-size: 0.8rem;
  text-decoration: none;
  white-space: nowrap;
}

.book-home:hover {
  background: #dbeafe;
}

.book-nav-btn {
  border: 1px solid #f97316;
  background: #fff7ed;
  color: #7c2d12;
  padding: 4px 8px;
  border-radius: 999px;
  font-size: 0.75rem;
  cursor: pointer;
  white-space: nowrap;
}

.book-nav-btn:hover {
  background: #fed7aa;
}

/* Main content area */
.book-main {
  max-width: 900px;
  margin: 12px auto 32px;
  padding: 0 16px 24px;
}

.book-loading {
  font-size: 0.9rem;
  color: #6b7280;
}

.book-content h2,
.book-content h3,
.book-content h4 {
  margin-top: 1.5em;
  color: #7c2d12;
}

.book-content p {
  line-height: 1.6;
  margin: 0.5em 0;
}

.book-content ul {
  padding-left: 1.2em;
}

/* Small screens */
@media (max-width: 640px) {
  .book-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .book-nav {
    justify-content: flex-start;
  }
}
/* ========== ORANGE UNIT-PILL NAV (overview + units) ========== */

.book-unit-nav {
  max-width: 900px;
  margin: 10px auto 8px;
  padding: 0 16px 4px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

/* Each row of pills */
.unit-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

/* Overview row gets a tiny bit more space below */
.unit-row--overview {
  margin-bottom: 4px;
}

/* Base pill look */
.unit-pill,
.unit-row a {
  display: inline-block;
  border: 2px solid #ff8a4c;
  padding: 2px 10px;
  border-radius: 999px;
  font-size: 0.85rem;
  text-decoration: none;
  color: #c85000;
  background: #fff7ed;
  white-space: nowrap;
}

/* Overview pill (current page) */
.overview-pill {
  border-color: #2563eb;
  color: #1d4ed8;
  background: #eff6ff;
}

/* Active unit (if you ever add .unit-active to one pill) */
.unit-active {
  background: #ffedd5;
  border-color: #ea580c;
  color: #9a3412;
}

/* Small screens: keep it readable */
/* Small screens: keep it readable */
@media (max-width: 640px) {
  .book-unit-nav {
    padding-inline: 12px;
  }

  .unit-pill,
  .unit-row a {
    font-size: 0.8rem;
    padding: 2px 8px;
  }
}

.unit-summary {
  margin-top: 32px;
  border-top: 1px solid rgba(0,0,0,0.06);
  padding-top: 16px;
}

.unit-summary-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
  margin-bottom: 20px;
}

@media (min-width: 768px) {
  .unit-summary-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.summary-card {
  padding: 12px 14px;
  border-radius: 10px;
  background: rgba(0,0,0,0.02);
}

.summary-card h3 {
  margin-top: 0;
  margin-bottom: 6px;
}

.summary-card ul {
  margin: 0;
  padding-left: 1.1rem;
}

.unit-summary-extra ol {
  padding-left: 1.5rem;
}


/* Hide the top “Unit 1 … Unit 20” pill row on phones */
@media (max-width: 768px) {
  .book-unit-nav {
    display: none;
  }
}

/* ===== Reader layout ===== */

.reader-header {
  margin-bottom: 24px;
}

.reader-intro {
  max-width: 60rem;
}

.reader-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
}

@media (min-width: 900px) {
  .reader-layout {
    grid-template-columns: 220px minmax(0, 1fr);
  }
}

.reader-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

@media (min-width: 900px) {
  .reader-nav {
    flex-direction: column;
  }
}

/* Make buttons look like your unit pills */
.reader-unit-btn {
  cursor: pointer;
  border: none;
  background: transparent;
  text-align: left;
}

.reader-unit-btn.is-active {
  font-weight: 600;
  box-shadow: 0 0 0 1px rgba(255, 128, 0, 0.7);
}

/* ===== Unit styling (similar to the nice Unit 1/2 layout) ===== */

.unit-article {
  margin-top: 8px;
  margin-bottom: 48px;
}

.unit-hero {
  margin-bottom: 24px;
}

.unit-hero h1 {
  font-size: 1.9rem;
  margin-bottom: 8px;
}

.unit-label {
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.8rem;
  opacity: 0.8;
  margin-bottom: 4px;
}

.unit-intro {
  max-width: 60rem;
}

.unit-section {
  margin-top: 28px;
}

.unit-section h2 {
  margin-bottom: 8px;
}

.unit-section h3 {
  margin-top: 16px;
  margin-bottom: 4px;
}

.formula {
  font-style: italic;
  margin: 8px 0 16px;
}

.tip-box {
  margin-top: 16px;
  padding: 12px 16px;
  border-radius: 8px;
  background: rgba(255, 165, 0, 0.06);
  border: 1px solid rgba(255, 165, 0, 0.4);
}

.definition-card {
  padding: 14px 16px;
  border-radius: 10px;
  background: rgba(0, 0, 0, 0.02);
  margin-top: 12px;
}

.definition-card h3 {
  margin-bottom: 6px;
}

.definition-card .example {
  margin-top: 8px;
}

.table-scroll {
  overflow-x: auto;
}

.unit-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 8px;
}

.unit-table th,
.unit-table td {
  padding: 8px 10px;
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  text-align: left;
}

.example {
  margin: 8px 0;
}

.breakdown-list {
  margin-top: 8px;
}

.practice-section ol,
.practice-section ul {
  padding-left: 1.5rem;
}

.next-unit {
  margin-top: 16px;
  font-weight: 500;
}

.next-unit a {
  margin-left: 6px;
}
.unit-mini-toc {
  margin: 1.5rem 0 2rem;
  padding: 1rem 1.25rem;
  border-radius: 0.75rem;
  background: #f7f7fb;
  border: 1px solid #e0e2f0;
  font-size: 0.95rem;
}

.unit-mini-toc-label {
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.unit-mini-toc ol {
  margin: 0;
  padding-left: 1.2rem;
}

.unit-mini-toc li {
  margin: 0.15rem 0;
}

.unit-mini-toc a {
  text-decoration: none;
}

.unit-mini-toc a:hover {
  text-decoration: underline;
}
/* === Landing page styles === */

.landing-article {
  max-width: 960px;
  margin: 0 auto;
}

.landing-hero {
  background: linear-gradient(135deg, #ff6f61, #ff9472);
  color: #fff;
  padding: 2.5rem 2rem;
  border-radius: 1.5rem;
  box-shadow: 0 18px 40px rgba(0,0,0,0.1);
  margin-bottom: 2.5rem;
}

.landing-badge {
  display: inline-block;
  background: rgba(255, 255, 255, 0.2);
  padding: 0.3rem 0.9rem;
  border-radius: 999px;
  font-size: 0.85rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.landing-title {
  font-size: 2.1rem;
  line-height: 1.2;
  margin-bottom: 1rem;
}

.landing-title span {
  display: block;
  font-weight: 400;
}

.landing-intro-text {
  font-size: 1rem;
  max-width: 46rem;
  margin-bottom: 0.75rem;
}

.landing-cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.5rem 0 0.75rem;
}

.landing-cta-primary,
.landing-cta-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.65rem 1.3rem;
  border-radius: 999px;
  font-weight: 600;
  text-decoration: none;
  font-size: 0.95rem;
}

.landing-cta-primary {
  background: #fff;
  color: #ff6f61;
}

.landing-cta-primary:hover {
  filter: brightness(0.95);
}

.landing-cta-secondary {
  border: 1px solid rgba(255,255,255,0.8);
  color: #fff;
  background: transparent;
}

.landing-meta {
  font-size: 0.85rem;
  opacity: 0.9;
}

.landing-main {
  padding: 2rem 0;
}

.landing-section {
  margin-bottom: 2.5rem;
}

.landing-section h2 {
  font-size: 1.4rem;
  margin-bottom: 0.75rem;
}

.landing-section-grid {
  display: grid;
  gap: 1rem;
}

.landing-point-card,
.feature-card {
  background: #fff;
  border-radius: 1rem;
  padding: 1rem 1.25rem;
  box-shadow: 0 8px 20px rgba(0,0,0,0.04);
  border: 1px solid rgba(0,0,0,0.03);
}

.landing-point-card h3,
.feature-card h3 {
  margin-top: 0;
  margin-bottom: 0.4rem;
  color: #cc4c3f; /* darker coral */
}

.landing-steps {
  display: grid;
  gap: 1rem;
}

.landing-step {
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
}

.landing-step-number {
  width: 2rem;
  height: 2rem;
  border-radius: 999px;
  background: #ff6f61;
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  flex-shrink: 0;
}

.landing-cta-section {
  text-align: center;
  background: #fff7f4;
  padding: 2rem 1.5rem;
  border-radius: 1.5rem;
  border: 1px solid rgba(255,111,97,0.2);
}

.landing-cta-text {
  margin-bottom: 1.25rem;
}

.landing-features-grid {
  display: grid;
  gap: 1rem;
}

/* Simple responsiveness */
@media (min-width: 720px) {
  .landing-section-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .landing-features-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .landing-steps {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .landing-hero {
    padding: 3rem;
  }
}

/* Integrated course edition: shared route, readable study cards and responsive reader. */
:root { --course-ink: #243e43; --course-teal: #146b65; }
.book-body { color: var(--course-ink); background: #f6f8f4; }
.book-header { position: relative; background: #fff; border-bottom: 1px solid #d5ded6; padding: 18px max(20px, calc((100vw - 1080px)/2)); }
.book-title { color: var(--course-teal); text-decoration: none; }
.book-main { max-width: 1080px; margin: 0 auto; padding: 24px; box-sizing: border-box; }
.book-main > .reader-main { max-width: 860px; margin: 0 auto; }
.book-subtitle { color: #4e6465; }
.course-hero { padding: 38px; background: #e7efdf; border-radius: 18px; margin-bottom: 30px; }
.course-hero h1 { color: #153f39; font-size: clamp(2rem, 5vw, 3.4rem); line-height: 1.15; margin: 16px 0 24px; }
.course-hero p { max-width: 690px; font-size: 1.1rem; line-height: 1.65; }
.eyebrow { font-size: .78rem !important; font-weight: 750; letter-spacing: .08em; color: #365d4f; }
.route-panel, .learning-card { padding: 24px; margin: 28px 0; border: 1px solid #d5e0d4; border-radius: 12px; background: #fff; }
.learning-card { background: #eef4e8; border-left: 5px solid var(--course-teal); }
.route-panel h2, .learning-card h2, .part-group h3 { margin-top: 0; color: var(--course-teal); }
.course-home p, .course-home li, .reader-main p, .reader-main li { line-height: 1.7; }
.part-group { margin: 36px 0; }
.toc-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.toc-card { padding: 22px; background: white; border: 1px solid #d5e0d4; border-radius: 12px; }
.toc-card h4 { font-size: 1.15rem; margin: 10px 0; }
.toc-card a { color: #145e58; }
.primary-link { display: inline-block; background: #146b65; color: white; padding: 12px 18px; border-radius: 8px; margin: 8px 16px 8px 0; text-decoration: none; font-weight: 650; }
.primary-link:hover { background: #0b504b; color: white; }
a { text-underline-offset: .2em; }
.reader-toolbar { max-width: 860px; margin: 0 auto 24px; }
.reader-toolbar label { display: block; font-weight: 700; margin-bottom: 8px; }
.reader-toolbar select { width: 100%; min-width: 0; max-width: 100%; padding: 12px; font: inherit; color: #243e43; border: 1px solid #8da6a0; border-radius: 8px; background: white; }
#reader-status { font-size: .85rem; color: #526767; }
details { border: 1px solid #b8cec7; padding: 14px 18px; border-radius: 8px; margin: 16px 0; background: #f5f9f6; }
summary { cursor: pointer; font-weight: 700; color: #145e58; line-height: 1.5; }
.model-answer { padding: 22px; border-left: 4px solid #8c783b; background: #fcfaf3; }
.unit-footer { display: flex; flex-wrap: wrap; gap: 18px; border-top: 1px solid #ccd9d1; margin-top: 36px; padding-top: 24px; }
.unit-footer p { flex-basis: 100%; }
.course-footer { max-width: 1000px; margin: 30px auto 0; padding: 24px; border-top: 1px solid #ccd9d1; color: #536664; font-size: .85rem; }
.unit-section, .anchor-alias, [id] { scroll-margin-top: 24px; }
.anchor-alias { display: block; height: 0; }
.filename { overflow-wrap: anywhere; font-size: .85rem; }
.table-scroll { overflow-x: auto; }
.unit-table { width: 100%; border-collapse: collapse; }
.unit-table th { text-align: left; }
.unit-table th, .unit-table td { padding: 12px; border-bottom: 1px solid #d5e0d4; vertical-align: top; }
.unit-mini-toc { margin: 24px 0; }
.unit-mini-toc ol { padding-left: 24px; }
.unit-article { overflow-wrap: anywhere; }
.skip-link { position: absolute; top: -100px; left: 12px; padding: 12px; background: white; z-index: 100; }
.skip-link:focus { top: 8px; }
:focus-visible { outline: 3px solid #aa6a19; outline-offset: 4px; }
@media (max-width: 640px) {
 .book-header { align-items: flex-start; gap: 12px; flex-direction: column; padding: 16px; }
 .book-nav { justify-content: flex-start; }
 .book-main { padding: 16px; }
 .course-hero { padding: 24px; }
 .route-panel, .learning-card { padding: 18px; }
 .toc-grid { grid-template-columns: 1fr; }
 .unit-table { font-size: .85rem; }
 .unit-table th, .unit-table td { padding: 8px; }
 .model-answer { padding: 16px; }
}