/*
=============================================================================
  TEXTBOOK SHELL — Shared Stylesheet
  All chapter pages link to this file. Changing styles here updates every
  chapter automatically. Do not embed styles directly in chapter HTML files.
=============================================================================
*/

/* ── COLOR TOKENS ── */
:root {
  --primary:       #6D28D9;
  --primary-dark:  #5B21B6;
  --h1-bg:         #6D28D9;
  --h2-bg:         #5B21B6;
  --h3-bg:         #4C1D95;
  --keyterm-color: #6D28D9;
  --cite-color:    #111827;
  --accent:        #f37d26;
  --text:          #1F2937;
  --bg:            #FFFFFF;
  --surface:       #F5F3FF;
  --border:        #D1D5DB;
  --img-border:    #9CA3AF;
  --nav-bg:        #1E1B4B;
}

/* ── RESET ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ── BASE ── */
body {
  font-family: 'Inter', sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--text);
  background: var(--bg);
}

/* ── NAV OVERLAY ── */
.nav-overlay {
  position: fixed; inset: 0;
  background: rgba(0,0,0,0.45);
  z-index: 900;
  opacity: 0; pointer-events: none;
  transition: opacity 0.3s;
}
.nav-overlay.open { opacity: 1; pointer-events: all; }

/* ── SLIDE-IN NAV PANEL ── */
.nav-panel {
  position: fixed;
  top: 0; left: -320px;
  width: 300px; height: 100%;
  background: var(--nav-bg);
  color: white;
  z-index: 1000;
  transition: left 0.3s ease;
  overflow-y: auto;
  padding: 24px 20px;
  display: flex;
  flex-direction: column;
}
.nav-panel.open { left: 0; }

.nav-book-title { font-size: 14px; font-weight: 700; color: white; line-height: 1.3; margin-bottom: 4px; }
.nav-chapter-label { font-size: 12px; color: #A5B4FC; margin-bottom: 16px; }

.nav-btn-row { display: flex; gap: 8px; margin-bottom: 4px; }
.nav-btn {
  flex: 1; padding: 8px 10px;
  background: #312E81; color: white;
  border: none; border-radius: 5px;
  font-size: 13px; font-weight: 500;
  font-family: 'Inter', sans-serif;
  cursor: pointer; text-align: center;
  text-decoration: none; display: block;
  transition: background 0.2s;
}
.nav-btn:hover { background: #3730A3; }
.nav-btn.home { width: 100%; margin-bottom: 8px; flex: none; }
.nav-btn.primary { background: var(--accent); color: #1C1917; }
.nav-btn.primary:hover { background: #d4631a; }

.nav-divider { border: none; border-top: 1px solid #312E81; margin: 16px 0; }
.nav-section-label { font-size: 10px; font-weight: 700; text-transform: uppercase; letter-spacing: 1.5px; color: #818CF8; margin-bottom: 8px; }

.nav-toc { list-style: none; }
.nav-toc a {
  display: block; padding: 6px 0 6px 12px;
  color: #C7D2FE; text-decoration: none;
  font-size: 13px; line-height: 1.4;
  border-left: 2px solid transparent;
  transition: all 0.15s;
}
.nav-toc a:hover,
.nav-toc a.active { color: white; border-left-color: var(--accent); }
.nav-toc .sub { padding-left: 24px; font-size: 12px; color: #818CF8; }
.nav-toc .sub.active,
.nav-toc .sub:hover { color: #C7D2FE; }

.nav-utility-row { display: flex; gap: 8px; margin-top: auto; padding-top: 16px; }

/* ── FLOATING MENU BUTTON ── */
.menu-btn {
  position: fixed; top: 16px; left: 16px; z-index: 800;
  background: var(--accent); color: white;
  border: none; width: 44px; height: 44px;
  border-radius: 50%; cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  box-shadow: 0 2px 10px rgba(243,125,38,0.4);
  transition: background 0.2s, transform 0.15s;
}
.menu-btn:hover { background: #d4631a; transform: scale(1.05); }

/* ── CONTENT WRAPPER ── */
.content-wrapper { max-width: 900px; margin: 0 auto; padding: 0 30px 80px; }

/* ── TITLE BAR (top of every chapter page) ── */
.title-bar {
  height: 60px;
  display: flex; align-items: center; justify-content: center;
  text-align: center;
  padding: 0 60px;
  font-size: 24px; font-weight: 800;
  letter-spacing: 2px; text-transform: uppercase;
  color: #9CA3AF; line-height: 1;
}

/* ── CHAPTER HERO ── */
.chapter-hero {
  background: var(--primary);
  color: white;
  padding: 52px 40px 52px;
  margin: 12px -30px 52px;
  position: relative;
  overflow: hidden;
  clip-path: polygon(0 0, 100% 0, 100% 100%, 0 88%);
}
/* Orange right-edge stripe */
.chapter-hero::after {
  content: '';
  position: absolute; top: 0; right: 0;
  width: 8px; height: 100%;
  background: var(--accent);
}
/* Decorative background circle */
.chapter-hero::before {
  content: '';
  position: absolute; right: -60px; top: -60px;
  width: 300px; height: 300px;
  border-radius: 50%;
  border: 40px solid rgba(255,255,255,0.06);
  pointer-events: none;
}
.hero-chapter-num {
  font-size: 11px; font-weight: 900;
  letter-spacing: 4px; text-transform: uppercase;
  color: var(--accent); margin-bottom: 10px;
  display: flex; align-items: center; gap: 10px;
}
.hero-chapter-num::after {
  content: '';
  display: block; flex: 1;
  height: 2px; background: var(--accent);
  opacity: 0.5; max-width: 80px;
}
.chapter-title {
  font-size: 38px; font-weight: 800; line-height: 1.15;
  text-shadow: 2px 3px 12px rgba(0,0,0,0.3);
  margin-bottom: 14px;
  background: none !important; padding: 0 !important;
  color: white !important; margin-top: 0 !important;
}
.chapter-subtitle { font-size: 15px; opacity: 0.82; max-width: 580px; line-height: 1.6; }

/* ── CHAPTER RESOURCE LINKS (top quick-links) ── */
.chapter-resources { display: flex; flex-wrap: wrap; gap: 10px; margin: 0 0 32px; }
.resource-link {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 10px 18px;
  background: var(--surface); border: 1.5px solid var(--primary);
  border-radius: 999px;
  color: var(--primary); font-weight: 700; font-size: 14px;
  text-decoration: none; transition: background 0.15s, color 0.15s;
}
.resource-link:hover { background: var(--primary); color: #fff; }

/* ── BODY TEXT ── */
p {
  text-align: justify;
  hyphens: auto; -webkit-hyphens: auto; -ms-hyphens: auto;
  margin-bottom: 20px;
}

/* ── SECTION HEADERS (all boxed) ── */
h1 {
  background: var(--h1-bg); color: white;
  padding: 13px 20px; font-size: 20px; font-weight: 700;
  text-shadow: 1px 2px 5px rgba(0,0,0,0.5);
  margin: 44px 0 40px;
}
h2 {
  background: var(--h2-bg); color: white;
  padding: 11px 20px; font-size: 17px; font-weight: 600;
  text-shadow: 1px 2px 4px rgba(0,0,0,0.4);
  margin: 32px 0 32px;
}
h3 {
  background: var(--h3-bg); color: white;
  padding: 9px 20px; font-size: 14px; font-weight: 600;
  text-shadow: 1px 1px 3px rgba(0,0,0,0.4);
  margin: 24px 0 28px;
}
/* Section number (e.g. "1.1") inside headers */
.section-num { color: #f3f126; }

/* ── LISTS ── */
ul, ol { padding-left: 28px; margin-bottom: 20px; }
li { margin-bottom: 6px; line-height: 1.5; }

/* ── TABLES ── */
table { width: 100%; border-collapse: collapse; margin: 24px 0; font-size: 14px; }
th { background: var(--primary); color: white; padding: 10px 14px; text-align: left; font-weight: 600; font-size: 13px; }
td { padding: 9px 14px; border-bottom: 1px solid var(--border); }
tr:nth-child(even) td { background: #F5F3FF; }
caption { font-size: 13px; color: #6B7280; font-style: italic; margin-bottom: 8px; text-align: left; }

/* ── KEY TERMS ── */
.key-term { font-weight: 700; color: var(--keyterm-color); cursor: pointer; position: relative; display: inline; }
.key-term-icon {
  display: inline-flex; align-items: center; justify-content: center;
  width: 14px; height: 14px;
  border: 1.5px solid var(--keyterm-color); border-radius: 50%;
  font-size: 9px; font-weight: 800; font-style: italic;
  color: var(--keyterm-color);
  margin-left: 2px; vertical-align: middle; position: relative; top: -1px;
}

/* ── CITATIONS ── */
.citation { color: var(--cite-color); cursor: pointer; position: relative; display: inline; font-weight: 600; }

/* ── POP-UP BOXES (key terms & citations) ── */
.popup-box {
  display: none; position: absolute;
  background: white; border: 1px solid var(--border); border-radius: 6px;
  padding: 14px 32px 14px 16px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.14);
  max-width: 300px; min-width: 200px;
  z-index: 600; font-size: 13px; font-weight: 400;
  color: var(--text); text-align: left;
  top: calc(100% + 6px); left: 0; line-height: 1.5;
}
.popup-box.active { display: block; }
.popup-box strong {
  display: block; font-size: 12px; font-weight: 700;
  color: var(--primary); margin-bottom: 6px;
  text-transform: uppercase; letter-spacing: 0.5px;
}
.citation .popup-box strong { color: var(--cite-color); }
.popup-close {
  position: absolute; top: 8px; right: 10px;
  background: none; border: none; font-size: 17px;
  cursor: pointer; color: #9CA3AF;
}
.popup-close:hover { color: var(--text); }
.popup-box .glossary-link {
  display: block; margin-top: 8px;
  font-size: 11px; font-weight: 600; letter-spacing: 0.4px; text-transform: uppercase;
  color: var(--keyterm-color); text-decoration: none;
}
.popup-box .glossary-link:hover { text-decoration: underline; }

/* ── IMAGES ── */
.textbook-figure { display: block; margin: 56px auto; text-align: center; position: relative; }
.textbook-figure img {
  border: 2px solid var(--img-border);
  box-shadow: 4px 4px 16px rgba(0,0,0,0.22);
  margin: 10px auto; width: 100%; height: auto; display: block; border-radius: 2px;
}
.textbook-figure figcaption {
  font-size: 13px; color: #6B7280; font-style: italic;
  margin-top: 10px; max-width: 640px; margin-left: auto; margin-right: auto;
}

/* ── FLOAT-RIGHT / FLOAT-LEFT FIGURES (portrait / inline, ~40% width) ── */
.textbook-figure.figure-right {
  float: right;
  width: 40%;
  margin: 2px 0 20px 28px;   /* tight top, space on left where text wraps */
  clear: right;
}
.textbook-figure.figure-left {
  float: left;
  width: 40%;
  margin: 2px 28px 20px 0;   /* tight top, space on right where text wraps */
  clear: left;
}

/* Full-width figures, question blocks, and section headers always clear any preceding float */
.textbook-figure:not(.figure-right):not(.figure-left),
.question-block,
section h1,
section h2,
section h3 { clear: both; }

@media (max-width: 640px) {
  .textbook-figure.figure-right,
  .textbook-figure.figure-left {
    float: none;
    width: 100%;
    margin: 32px auto;
  }
}

/* ── SENSITIVE / EXPLICIT MEDIA (blur + click-to-reveal content warning) ── */
.sensitive-media {
  position: relative; display: block; overflow: hidden;
  width: 100%; margin: 10px auto; border-radius: 2px;
  border: 2px solid var(--img-border);
  box-shadow: 4px 4px 16px rgba(0,0,0,0.22);
}
.sensitive-media img {
  display: block; margin: 0; border: none; box-shadow: none; border-radius: 0;
  transition: filter 0.25s ease;
}
.sensitive-media:not(.revealed) img { filter: blur(28px); }
.sensitive-reveal {
  position: absolute; inset: 0; width: 100%; height: 100%;
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 6px;
  padding: 16px; border: none; cursor: pointer; text-align: center;
  background: rgba(31,41,55,0.55); color: #fff;
  font-family: inherit; -webkit-tap-highlight-color: transparent;
  transition: background 0.15s ease;
}
.sensitive-media.revealed .sensitive-reveal { display: none; }
.sensitive-reveal:hover, .sensitive-reveal:focus-visible { background: rgba(31,41,55,0.68); }
.sensitive-reveal-icon { font-size: 30px; line-height: 1; }
.sensitive-reveal-title { font-weight: 700; font-size: 15px; letter-spacing: 0.02em; }
.sensitive-reveal-sub { font-size: 13px; max-width: 340px; opacity: 0.95; }
.sensitive-hide {
  position: absolute; top: 8px; right: 8px; display: none;
  font-family: inherit; font-size: 12px; font-weight: 600; color: #fff;
  background: rgba(31,41,55,0.72); border: none; border-radius: 4px;
  padding: 5px 11px; cursor: pointer; transition: background 0.15s ease;
}
.sensitive-media.revealed .sensitive-hide { display: inline-block; }
.sensitive-hide:hover, .sensitive-hide:focus-visible { background: rgba(31,41,55,0.92); }

/* ── FIGURE ENLARGE BUTTON ── */
.fig-enlarge-btn {
  position: absolute;
  top: -14px; right: -14px;
  width: 32px; height: 32px;
  background: rgba(255,255,255,0.92) url('img/enhance-img.png') center/18px 18px no-repeat;
  border: 1px solid rgba(0,0,0,0.12);
  border-radius: 5px;
  cursor: pointer;
  box-shadow: 0 1px 5px rgba(0,0,0,0.18);
  transition: background-color 0.15s, transform 0.1s;
  z-index: 5;
}
.fig-enlarge-btn:hover {
  background-color: #fff;
  transform: scale(1.08);
}
/* "Click to enlarge" tooltip */
.fig-enlarge-btn::after {
  content: 'Click to enlarge';
  position: absolute;
  top: calc(100% + 6px);
  right: 14px;
  background: rgba(0,0,0,0.74);
  color: #fff;
  font-size: 11px;
  font-weight: 500;
  font-style: normal;
  padding: 4px 9px;
  border-radius: 4px;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.15s;
}
.fig-enlarge-btn:hover::after { opacity: 1; }

/* ── LIGHTBOX ── */
.lb-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.72);
  z-index: 3000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  animation: lbFadeIn 0.18s ease;
}
@keyframes lbFadeIn { from { opacity: 0; } to { opacity: 1; } }
.lb-modal {
  background: #fff;
  border-radius: 8px;
  max-width: min(95vw, 1200px);
  max-height: 95vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: 0 12px 60px rgba(0,0,0,0.45);
  animation: lbSlideUp 0.18s ease;
}
@keyframes lbSlideUp { from { transform: translateY(12px); opacity: 0; } to { transform: none; opacity: 1; } }
.lb-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 13px 18px;
  border-bottom: 1px solid #E5E7EB;
  flex-shrink: 0;
}
.lb-title {
  font-size: 14px;
  font-weight: 600;
  color: #111827;
  letter-spacing: 0.1px;
}
.lb-close {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 22px;
  line-height: 1;
  color: #6B7280;
  padding: 0 2px;
  transition: color 0.15s;
}
.lb-close:hover { color: #111; }
.lb-body {
  overflow: auto;
  padding: 20px 24px 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.lb-body img {
  max-width: 100%;
  max-height: calc(95vh - 130px);
  height: auto;
  width: auto;
  object-fit: contain;
  display: block;
  border-radius: 2px;
}
.lb-caption {
  font-size: 12.5px;
  color: #6B7280;
  font-style: italic;
  text-align: center;
  margin-top: 14px;
  max-width: 720px;
  line-height: 1.5;
}
.lb-header-actions { display: flex; align-items: center; gap: 14px; }
.lb-download {
  display: inline-flex; align-items: center; gap: 6px;
  background: var(--primary); color: #fff;
  font-size: 12.5px; font-weight: 600;
  padding: 6px 13px; border-radius: 6px;
  text-decoration: none; white-space: nowrap;
  transition: background 0.15s;
}
.lb-download:hover, .lb-download:focus-visible { background: var(--primary-dark); }

/* Standalone image-guide call-to-action (opens a downloadable image in the lightbox) */
.image-guide-cta { text-align: center; margin: 24px 0; }
.image-guide-link {
  display: inline-flex; align-items: center; gap: 9px;
  background: var(--surface); color: var(--primary);
  border: 1.5px solid var(--primary);
  font-family: inherit; font-size: 15px; font-weight: 600;
  padding: 12px 22px; border-radius: 999px;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, box-shadow 0.15s;
}
.image-guide-link:hover, .image-guide-link:focus-visible {
  background: var(--primary); color: #fff;
  box-shadow: 0 4px 14px rgba(109,40,217,0.28);
}
.image-guide-icon { font-size: 18px; line-height: 1; }

/* ── VIDEO EMBEDS ── */
.video-wrapper {
  position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden;
  margin: 56px 10px;
  border: 2px solid var(--img-border);
  box-shadow: 4px 4px 16px rgba(0,0,0,0.22);
}
.video-wrapper iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: 0; }

/* ── INTERACTIVE APP EMBEDS (H5P / point-and-click widgets) ── */
.interactive-embed { margin: 56px auto; max-width: 620px; text-align: center; }
.interactive-embed-title {
  font-weight: 700; color: var(--primary); font-size: 13px;
  letter-spacing: 0.06em; text-transform: uppercase; margin: 0 0 4px;
}
.interactive-embed-intro {
  font-size: 14px; color: var(--text); line-height: 1.5;
  margin: 0 auto 14px; max-width: 560px;
}
/* Square (1:1) wrapper — matches the H5P Image Hotspots render */
.interactive-frame {
  position: relative; width: 100%; padding-bottom: 100%; height: 0;
  overflow: hidden; background: #fff;
  border: 2px solid var(--img-border);
  box-shadow: 4px 4px 16px rgba(0,0,0,0.22); border-radius: 2px;
}
.interactive-frame iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: 0; }
.interactive-embed figcaption {
  font-size: 13px; color: #6B7280; font-style: italic; margin-top: 10px;
}
/* Fixed-height variant for self-paginating app embeds (e.g., a multi-step quiz)
   that need a consistent vertical stage regardless of width. */
.interactive-embed.app-embed { max-width: 680px; }
.interactive-frame.frame-fixed { padding-bottom: 0; height: 780px; }
@media (max-width: 700px) {
  .interactive-frame.frame-fixed { height: 720px; }
}
/* Fixed-pixel app embeds that do NOT reflow (e.g., a 720×450 text-message sim).
   The iframe renders at native size and is scaled to fit the container by
   textbook.js (sets --embed-scale + the frame height); nothing is clipped. */
.interactive-embed.embed-fixed { max-width: 720px; }
.interactive-frame.frame-720x450 { padding-bottom: 0; height: auto; aspect-ratio: 720 / 450; }
/* Landscape H5P image-slider embeds (16:9 image + a strip of nav chrome). */
.interactive-embed.embed-slider { max-width: 680px; }
.interactive-frame.frame-slider { padding-bottom: 0; height: auto; aspect-ratio: 1.6; }
.interactive-frame.frame-720x450 iframe {
  width: 720px; height: 450px;
  transform-origin: top left;
  transform: scale(var(--embed-scale, 1));
}

/* ── YOUTUBE FACADE (lazy-load thumbnail) ── */
.yt-facade {
  position: absolute; inset: 0;
  cursor: pointer;
  background: #111 center/cover no-repeat;
  display: flex; align-items: center; justify-content: center;
}
/* ── YOUTUBE EXTERNAL LINK CARD (for non-embeddable videos) ── */
.yt-ext-link {
  position: absolute; inset: 0;
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  text-decoration: none;
  background: #111 center/cover no-repeat;
  gap: 14px;
}
/* Shared play button for both */
.yt-play-btn {
  width: 68px; height: 48px;
  background: rgba(220, 20, 20, 0.92);
  border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  transition: background 0.18s, transform 0.12s;
}
.yt-facade:hover .yt-play-btn,
.yt-ext-link:hover .yt-play-btn { background: #ff0000; transform: scale(1.07); }
.yt-play-btn::after {
  content: '';
  border: 13px solid transparent;
  border-left: 21px solid #fff;
  border-right: none;
  margin-left: 6px;
}
/* "Watch on YouTube" badge shown on link cards */
.yt-ext-label {
  color: #fff;
  font-size: 13px; font-weight: 700;
  letter-spacing: 0.3px;
  background: rgba(0,0,0,0.58);
  padding: 6px 16px;
  border-radius: 20px;
}
.video-caption {
  font-size: 13px; color: #6B7280; font-style: italic;
  text-align: center; margin-top: -40px; margin-bottom: 24px;
}

/* ── QUESTION BLOCKS ── */
.question-block {
  background: var(--surface);
  border-left: 5px solid var(--accent);
  border-radius: 0 6px 6px 0;
  padding: 20px 24px; margin: 64px 0;
}
.question-type-label {
  font-size: 10px; font-weight: 700;
  text-transform: uppercase; letter-spacing: 2px;
  color: var(--primary); margin-bottom: 10px;
}
.question-text {
  font-weight: 600; font-size: 15px; margin-bottom: 16px;
  text-align: left; hyphens: none; color: var(--text);
}

/* MCQ / True-False answer options */
.mcq-options { display: flex; flex-direction: column; gap: 8px; }
.answer-option {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 10px 14px; background: white;
  border: 2px solid var(--border); border-radius: 6px;
  cursor: pointer; font-size: 14px; transition: all 0.15s; text-align: left;
}
.answer-option:hover:not(.locked) { border-color: var(--primary); background: #F5F3FF; }
.answer-option.selected { border-color: var(--primary); background: #F5F3FF; }
.answer-option.correct { border-color: #16A34A; background: #F0FDF4; color: #15803D; }
.answer-option.incorrect { border-color: var(--primary-dark); background: #EDE9FE; color: #4C1D95; }
.answer-letter { font-weight: 700; min-width: 20px; color: var(--primary); flex-shrink: 0; }
.answer-option.correct .answer-letter { color: #16A34A; }
.answer-option.incorrect .answer-letter { color: #4C1D95; }

/* Matching */
.match-container { display: flex; flex-direction: column; gap: 10px; }
.match-row { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.match-term {
  font-weight: 600; font-size: 14px; background: white;
  border: 2px solid var(--border); padding: 8px 14px;
  border-radius: 6px; min-width: 160px; flex: 1;
}
.match-select {
  flex: 2; padding: 8px 12px; border: 2px solid var(--border);
  border-radius: 6px; font-family: 'Inter', sans-serif;
  font-size: 14px; background: white; cursor: pointer;
}
.match-select.correct { border-color: #16A34A; background: #F0FDF4; }
.match-select.incorrect { border-color: var(--primary); background: #EDE9FE; }

/* Sorting */
.sort-list { list-style: none; display: flex; flex-direction: column; gap: 8px; }
.sort-item {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 14px; background: white;
  border: 2px solid var(--border); border-radius: 6px;
  cursor: grab; font-size: 14px; user-select: none;
}
.sort-item:active { cursor: grabbing; }
.sort-handle { color: #9CA3AF; font-size: 18px; flex-shrink: 0; }
.sort-item.correct { border-color: #16A34A; background: #F0FDF4; }
.sort-item.incorrect { border-color: var(--primary); background: #EDE9FE; }

/* Fill-in-the-blank */
.fitb-sentence { font-size: 15px; font-weight: 500; line-height: 2; margin-bottom: 12px; text-align: left; hyphens: none; }
.fitb-input {
  border: none; border-bottom: 2px solid var(--primary);
  font-family: 'Inter', sans-serif; font-size: 15px;
  font-weight: 600; color: var(--primary);
  background: transparent; width: 140px;
  text-align: center; outline: none; padding: 2px 4px;
}
.fitb-input.correct { border-color: #16A34A; color: #15803D; }
.fitb-input.incorrect { border-color: var(--primary-dark); color: #4C1D95; }

/* Click-on-target */
.cot-image-wrap { position: relative; display: inline-block; cursor: crosshair; margin: 10px auto; }
.cot-image-wrap img { display: block; max-width: 100%; }
.selection-circle {
  position: absolute; width: 25px; height: 25px;
  border-radius: 50%; border: 3px solid var(--accent);
  background: rgba(243,125,38,0.2);
  transform: translate(-50%, -50%);
  pointer-events: none; display: none;
}

/* Submit button */
.submit-btn {
  margin-top: 14px; background: var(--primary); color: white;
  border: none; padding: 9px 22px; border-radius: 5px;
  font-size: 14px; font-weight: 600; font-family: 'Inter', sans-serif;
  cursor: pointer; transition: background 0.2s;
}
.submit-btn:hover { background: var(--primary-dark); }
.submit-btn:disabled { background: #9CA3AF; cursor: default; }

/* Explanation box */
.explanation-box {
  display: none; margin-top: 14px;
  background: #FFFBEB; border: 1px solid #FCD34D;
  border-radius: 5px; padding: 12px 16px;
  font-size: 13px; color: #78350F; line-height: 1.6;
}
.explanation-box.show { display: block; }

/* ── FUN FACT / CALLOUT BOX ── */
.fact-box {
  background: var(--surface);
  border-left: 4px solid var(--accent);
  border-radius: 8px;
  padding: 16px 20px;
  margin: 28px 0;
}
.fact-box p { margin: 0; }
.fact-box p + p { margin-top: 10px; }
.fact-box .fact-label { color: var(--primary); }
.fact-box a { display: block; }
.fact-box img {
  display: block; max-width: 100%; height: auto; margin: 14px auto 0;
  border: 2px solid var(--img-border); border-radius: 6px;
  box-shadow: 4px 4px 16px rgba(0,0,0,0.18); transition: box-shadow 0.15s ease;
}
.fact-box a:hover img, .fact-box a:focus-visible img { box-shadow: 4px 4px 22px rgba(109,40,217,0.40); }

/* ── STUDY GUIDE ANSWER GUIDE (collapsible) ── */
.answer-guide { margin: 24px 0 28px; border: 1.5px solid var(--border); border-radius: 8px; overflow: hidden; }
.answer-guide > summary {
  cursor: pointer; padding: 14px 18px; font-weight: 700; color: var(--primary);
  background: var(--surface); list-style: none; -webkit-tap-highlight-color: transparent;
}
.answer-guide > summary::-webkit-details-marker { display: none; }
.answer-guide > summary::before { content: '▸ '; }
.answer-guide[open] > summary::before { content: '▾ '; }
.answer-guide-inner { padding: 6px 18px 10px; }

/* ── STUDY GUIDE ── */
.study-guide-section { border-top: 2px solid var(--border); margin-top: 40px; padding-top: 24px; }
.study-guide-intro { font-style: italic; color: #6B7280; margin-bottom: 8px; line-height: 1.6; }
.study-guide-list { margin-bottom: 28px; }
.study-guide-list li { margin-bottom: 12px; line-height: 1.6; }

/* ── GLOSSARY ── */
.glossary-section { border-top: 2px solid var(--border); margin-top: 40px; padding-top: 24px; }
.glossary-list { list-style: none; padding: 0; }
.glossary-list .g-term { padding: 10px 0; border-bottom: 1px solid var(--border); line-height: 1.6; }
.glossary-list .g-term dt { font-size: 15px; font-weight: 700; color: var(--keyterm-color); display: block; }
.glossary-list .g-term dd { font-size: 14px; font-weight: 400; color: #111827; margin: 3px 0 0 20px; line-height: 1.6; }

/* ── REFERENCES ── */
.references-section { border-top: 2px solid var(--border); margin-top: 56px; padding-top: 24px; }
.references-list { list-style: none; padding: 0; }
.references-list li {
  font-size: 14px; line-height: 1.7;
  padding-left: 36px; text-indent: -36px;
  text-align: left; margin-bottom: 10px;
}

/* ── SITE FOOTER ── */
.site-footer {
  background: var(--nav-bg);
  padding: 28px 24px;
  margin-top: 48px;
}
.site-footer-inner {
  max-width: 780px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}
.cc-badge {
  height: 31px;
  width: auto;
  flex-shrink: 0;
  opacity: 0.9;
  transition: opacity 0.2s;
}
.cc-badge:hover { opacity: 1; }
.cc-text {
  font-size: 13px;
  line-height: 1.6;
  color: rgba(255,255,255,0.65);
}
.cc-text strong { color: rgba(255,255,255,0.9); font-weight: 600; }
.cc-text a { color: #A5B4FC; text-decoration: none; }
.cc-text a:hover { color: #f3f126; text-decoration: underline; }
@media (max-width: 600px) {
  .site-footer { padding: 24px 16px; }
  .cc-text { font-size: 12px; }
}

/* ── PRINT ── */
@media print {
  .menu-btn, .nav-panel, .nav-overlay { display: none !important; }
  .chapter-hero { clip-path: none !important; }
  .explanation-box, .submit-btn { display: none !important; }
  .answer-option { break-inside: avoid; border: 1px solid #ccc; }
  .content-wrapper { padding: 0 !important; }
  body { font-size: 12pt; }
}

/* ── MOBILE ── */
@media (max-width: 640px) {
  .content-wrapper { padding: 0 16px 60px; }
  .chapter-hero { padding: 36px 20px 52px; margin: 8px -16px 36px; }
  .chapter-title { font-size: 26px !important; }
  h1 { font-size: 17px; }
  h2 { font-size: 14px; }
  h3 { font-size: 13px; }
  .match-row { flex-direction: column; }
  .match-term, .match-select { width: 100%; }
}