@import url('https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/static/pretendard.css');
@import url('https://fonts.googleapis.com/earlyaccess/nanummyeongjoyethangul.css');

:root {
  /* Light Mode Tokens */
  --bg-main: #f0f4f9;
  --bg-card: rgba(255, 255, 255, 0.85);
  --bg-header: #0a3560;
  --bg-nav: #e3ecf5;
  --bg-tab-hover: #d2e3f3;
  --border-color: rgba(181, 212, 244, 0.5);
  --border-focus: #378add;
  --text-main: #1e293b;
  --text-muted: #5a8ab8;
  --text-white: #ffffff;
  
  /* Brand Colors */
  --primary: #0c447c;
  --primary-hover: #185fa5;
  --secondary: #378add;
  --success: #2e7d32;
  --success-bg: #e8f5e9;
  --success-border: #81c784;
  --error: #c62828;
  --error-bg: #ffebee;
  --error-border: #e57373;
  
  /* Concept-specific styling (mapped from light modes) */
  --c-badge-bg: #d0e7f8;
  --c-badge-text: #185fa5;
  --c-card-bg: #ffffff;
  --c-tip-bg: #e1f0fc;
  --c-tip-border: #85b7eb;
  --c-tip-text: #042c53;
  --c-tbl-th: #d0e7f8;
  --c-tbl-tr-even: #f0f7fd;
  
  /* Quiz styling */
  --q-bg: #f5f9f0;
  --q-card-border: #b8d898;
  --q-badge-bg: #c8e0a0;
  --q-badge-text: #173404;
  --q-prog-wrap: #d8ecc0;
  --q-opt-bg: #f9fdf5;
  --q-opt-border: #c0d8a0;
  --q-opt-hover: #eaf3de;
  
  /* Diagram styling */
  --d-bg: #fdf8f0;
  --d-card-border: #ef9f27;
  --d-lbl-text: #854f0b;
  
  /* UI Utilities */
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.05);
  --shadow-md: 0 10px 25px -5px rgba(12, 68, 124, 0.08), 0 8px 10px -6px rgba(12, 68, 124, 0.08);
  --shadow-lg: 0 20px 25px -5px rgba(0,0,0,0.1), 0 10px 10px -5px rgba(0,0,0,0.04);
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font: 'Pretendard', 'Nanum Myeongjo Yet Hangul', '함초롬바탕', 'Hamchorom Batang', '한컴바탕', 'Hancom Batang', '한컴고딕', 'Hancom Gothic', 'Nanum Myeongjo', serif, -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
}

/* Dark Mode Tokens */
body.dark-mode {
  --bg-main: #0f172a;
  --bg-card: rgba(30, 41, 59, 0.7);
  --bg-header: #020617;
  --bg-nav: #1e293b;
  --bg-tab-hover: #334155;
  --border-color: rgba(51, 65, 85, 0.5);
  --border-focus: #38bdf8;
  --text-main: #f1f5f9;
  --text-muted: #94a3b8;
  
  --primary: #38bdf8;
  --primary-hover: #7dd3fc;
  --secondary: #0ea5e9;
  
  /* Concept Dark Modes */
  --c-badge-bg: #0f2d4a;
  --c-badge-text: #38bdf8;
  --c-card-bg: #1e293b;
  --c-tip-bg: #112235;
  --c-tip-border: #1e3a5f;
  --c-tip-text: #e2e8f0;
  --c-tbl-th: #1e3a8a;
  --c-tbl-tr-even: #1e293b;
  
  /* Quiz Dark Modes */
  --q-bg: #141d17;
  --q-card-border: #2e4a3f;
  --q-badge-bg: #1b382b;
  --q-badge-text: #4ade80;
  --q-prog-wrap: #1c3527;
  --q-opt-bg: #1e293b;
  --q-opt-border: #334155;
  --q-opt-hover: #1e3a27;
  
  /* Diagram Dark Modes */
  --d-bg: #1c160c;
  --d-card-border: #b45309;
  --d-lbl-text: #fbbf24;
}

/* General Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: var(--font);
  background-color: var(--bg-main);
  color: var(--text-main);
  min-height: 100vh;
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
  overflow-x: hidden;
}

/* Header & Navigation */
header {
  background-color: var(--bg-header);
  color: var(--text-white);
  padding: 16px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.header-title-container {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.header-logo-mini {
  height: 24px;
  width: auto;
}

header h1 {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

header span {
  font-size: 0.75rem;
  opacity: 0.7;
  margin-top: 2px;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

/* Icons & Switches */
.toggle-btn {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-white);
  padding: 8px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
  font-size: 1.2rem;
}

.toggle-btn:hover {
  background-color: rgba(255, 255, 255, 0.1);
}

.home-btn {
  color: var(--text-white);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  background-color: rgba(255,255,255,0.15);
  transition: var(--transition);
}

.home-btn:hover {
  background-color: rgba(255,255,255,0.25);
}

/* Tabs */
.tab-nav {
  display: flex;
  background-color: var(--bg-nav);
  padding: 0 10px;
  border-bottom: 1px solid var(--border-color);
  overflow-x: auto;
  scrollbar-width: none; /* Hide scrollbar for Firefox */
  -webkit-overflow-scrolling: touch;
  position: sticky;
  top: 61px; /* Right below header */
  z-index: 99;
}

.tab-nav::-webkit-scrollbar {
  display: none; /* Hide scrollbar for Chrome/Safari */
}

.tab-btn {
  padding: 14px 20px;
  font-size: 0.9rem;
  font-weight: 600;
  border: none;
  background: transparent;
  cursor: pointer;
  color: var(--text-muted);
  border-bottom: 3px solid transparent;
  white-space: nowrap;
  transition: var(--transition);
  flex: 1;
  text-align: center;
  min-width: 100px;
}

.tab-btn:hover:not(.active) {
  color: var(--text-main);
  background-color: var(--bg-tab-hover);
}

.tab-btn.active {
  color: var(--primary);
  border-bottom-color: var(--border-focus);
  background-color: var(--bg-card);
}

/* Content Container */
.container {
  max-width: 800px;
  margin: 1.5rem auto;
  padding: 0 16px;
  padding-bottom: 80px; /* Safe space at bottom for mobile */
}

.panel {
  display: none;
  animation: fadeIn 0.4s ease;
}

.panel.show {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Cards & Layout */
.card {
  background-color: var(--bg-card);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 24px;
  margin-bottom: 20px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

/* Concept Formatting (Mapped from raw HTML content) */
.c-badge {
  display: inline-flex;
  align-items: center;
  font-size: 0.75rem;
  font-weight: 600;
  background-color: var(--c-badge-bg);
  color: var(--c-badge-text);
  padding: 4px 12px;
  border-radius: 50px;
  margin-bottom: 12px;
}

.c-h1 {
  font-size: 1.6rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 4px;
}

.c-sub {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 20px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-color);
}

.c-h2 {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 24px 0 12px;
  color: var(--primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.c-h2::before {
  content: '';
  width: 4px;
  height: 16px;
  background-color: var(--border-focus);
  border-radius: var(--radius-sm);
  display: block;
  flex-shrink: 0;
}

.c-body {
  font-size: 0.95rem;
  line-height: 1.8;
  margin-bottom: 16px;
  color: var(--text-main);
}

.c-key {
  display: inline-block;
  background-color: #dceeff;
  color: #0c447c;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 700;
}
body.dark-mode .c-key {
  background-color: #1e3a5f;
  color: #38bdf8;
}

.c-key2 {
  display: inline-block;
  background-color: #d6f0e8;
  color: #0f6e56;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 700;
}
body.dark-mode .c-key2 {
  background-color: #11352b;
  color: #4ade80;
}

.c-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  margin: 16px 0;
}

.c-card {
  background-color: var(--c-card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 16px;
  text-align: center;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
}

.c-card:hover {
  transform: translateY(-2px);
  border-color: var(--border-focus);
  box-shadow: var(--shadow-md);
}

.c-card-h {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 8px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border-color);
}

.c-card-b {
  font-size: 0.8rem;
  line-height: 1.6;
  color: var(--text-main);
}

.c-card-t {
  display: inline-block;
  margin-top: 8px;
  font-size: 0.7rem;
  background-color: var(--bg-main);
  color: var(--text-muted);
  padding: 2px 8px;
  border-radius: 50px;
}

.c-ex {
  background-color: var(--bg-card);
  border-left: 4px solid var(--border-focus);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: 16px;
  margin: 16px 0;
  font-size: 0.9rem;
  box-shadow: var(--shadow-sm);
}

.c-ex-lbl {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--secondary);
  text-transform: uppercase;
  margin-bottom: 6px;
  letter-spacing: 0.05em;
}

.c-tip {
  background-color: var(--c-tip-bg);
  border: 1px solid var(--c-tip-border);
  border-radius: var(--radius-md);
  padding: 16px 20px;
  margin: 20px 0;
  font-size: 0.9rem;
  color: var(--c-tip-text);
  box-shadow: var(--shadow-sm);
}

.c-tip-lbl {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--c-badge-text);
  margin-bottom: 6px;
  letter-spacing: 0.05em;
}

.c-tbl-wrapper {
  overflow-x: auto;
  margin: 16px 0;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
}

.c-tbl {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
  text-align: left;
}

.c-tbl th {
  background-color: var(--c-tbl-th);
  color: var(--text-main);
  font-weight: 700;
  padding: 10px 14px;
  border-bottom: 2px solid var(--border-color);
}

.c-tbl td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-main);
}

.c-tbl td,
.c-tbl th {
  /* Keep Korean words/phrases intact when a cell must wrap instead of
     breaking mid-syllable between any two Hangul characters. */
  word-break: keep-all;
}

.c-tbl tr:nth-child(even) td {
  background-color: var(--c-tbl-tr-even);
}

.svg-box {
  background-color: var(--c-card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px;
  margin: 16px 0;
  text-align: center;
  box-shadow: var(--shadow-sm);
}

.svg-lbl {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.svg-box svg {
  display: block;
  margin: 0 auto;
  max-height: 250px;
}

/* Quiz Interface */
.panel-q {
  background-color: var(--q-bg);
  border-radius: var(--radius-lg);
  padding: 20px;
  border: 1px solid rgba(184, 216, 152, 0.3);
}

.q-badge {
  display: inline-flex;
  align-items: center;
  font-size: 0.75rem;
  font-weight: 700;
  background-color: var(--q-badge-bg);
  color: var(--q-badge-text);
  padding: 4px 12px;
  border-radius: 50px;
  margin-bottom: 16px;
}

.q-prog-wrap {
  background-color: var(--q-prog-wrap);
  border-radius: var(--radius-md);
  padding: 12px 16px;
  margin-bottom: 20px;
  display: flex;
  align-items: center;
  gap: 16px;
}

.q-prog-bar {
  flex: 1;
  height: 8px;
  background-color: rgba(0, 0, 0, 0.08);
  border-radius: 50px;
  overflow: hidden;
}

.q-prog-fill {
  height: 100%;
  background-color: var(--success);
  border-radius: 50px;
  width: 0%;
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.q-prog-txt {
  font-size: 0.8rem;
  color: var(--q-badge-text);
  font-weight: 700;
  white-space: nowrap;
}

.q-bogi {
  margin: 10px 0 4px;
  padding: 14px 18px;
  background-color: var(--bg-card);
  border: 1px dashed var(--border-focus);
  border-radius: var(--radius-sm);
}

.q-bogi-lbl {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--secondary);
  letter-spacing: 0.08em;
  margin-bottom: 8px;
  padding: 2px 12px;
  border: 1px solid var(--border-focus);
  border-radius: 50px;
}

.q-bogi-body {
  font-size: 0.9rem;
  line-height: 1.9;
  color: var(--text-main);
}

.q-card {
  background-color: var(--bg-card);
  border: 1px solid var(--q-card-border);
  border-radius: var(--radius-md);
  padding: 24px;
  margin-bottom: 20px;
  box-shadow: var(--shadow-sm);
}

.q-hd {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-bottom: 14px;
}

.q-nb {
  font-size: 0.7rem;
  font-weight: 700;
  background-color: var(--q-prog-wrap);
  color: var(--q-badge-text);
  padding: 3px 8px;
  border-radius: 4px;
}

.q-tb {
  font-size: 0.7rem;
  font-weight: 700;
  background-color: var(--q-badge-bg);
  color: var(--q-badge-text);
  padding: 3px 8px;
  border-radius: 4px;
}

.q-txt {
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.6;
  margin-bottom: 16px;
}

.q-pass {
  background-color: rgba(255, 255, 255, 0.6);
  border-left: 4px solid var(--success-border);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 16px;
  margin-bottom: 20px;
  font-size: 0.9rem;
  line-height: 1.8;
  white-space: pre-line;
}
body.dark-mode .q-pass {
  background-color: rgba(15, 23, 42, 0.6);
}

.q-opts {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.q-opt {
  width: 100%;
  text-align: left;
  padding: 14px 18px;
  font-size: 0.9rem;
  line-height: 1.5;
  border: 1px solid var(--q-opt-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  background-color: var(--q-opt-bg);
  color: var(--text-main);
  font-family: var(--font);
  transition: var(--transition);
}

.q-opt:hover:not(:disabled) {
  background-color: var(--q-opt-hover);
  border-color: var(--success);
  transform: translateX(4px);
}

.q-opt.correct {
  background-color: var(--success-bg) !important;
  border-color: var(--success) !important;
  color: var(--success) !important;
  font-weight: 700;
}

.q-opt.wrong {
  background-color: var(--error-bg) !important;
  border-color: var(--error) !important;
  color: var(--error) !important;
}

.q-opt:disabled {
  cursor: default;
}

/* Short Answer Input */
.q-input-wrap {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 12px;
}

.q-input {
  width: 100%;
  padding: 14px 16px;
  font-size: 0.95rem;
  font-family: var(--font);
  border: 1.5px solid var(--border-color);
  border-radius: var(--radius-md);
  background-color: var(--bg-card);
  color: var(--text-main);
  outline: none;
  transition: var(--transition);
}

.q-input:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(55, 138, 221, 0.15);
}

.q-submit-btn {
  padding: 12px 20px;
  font-size: 0.9rem;
  font-weight: 700;
  font-family: var(--font);
  background-color: var(--bg-header);
  color: var(--text-white);
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  text-align: center;
}

.q-submit-btn:hover:not(:disabled) {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
}

.q-submit-btn:disabled {
  opacity: 0.5;
  cursor: default;
}

/* Feedback & Explanations */
.q-fb {
  margin-top: 16px;
  padding: 16px;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  line-height: 1.7;
  display: none;
  animation: slideDown 0.3s ease;
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

.q-fb.correct {
  background-color: var(--success-bg);
  color: var(--success);
  border: 1px solid var(--success-border);
  display: block;
}

.q-fb.wrong {
  background-color: var(--error-bg);
  color: var(--error);
  border: 1px solid var(--error-border);
  display: block;
}

.q-fb strong {
  display: block;
  margin-bottom: 4px;
}

/* Short answer self check panel */
.self-check-wrap {
  display: flex;
  gap: 10px;
  margin-top: 12px;
}

.self-btn {
  flex: 1;
  padding: 10px;
  border-radius: var(--radius-sm);
  border: none;
  font-weight: 700;
  font-family: var(--font);
  cursor: pointer;
  text-align: center;
  transition: var(--transition);
}

.self-btn.yes {
  background-color: var(--success);
  color: var(--text-white);
}

.self-btn.yes:hover {
  background-color: #235e27;
}

.self-btn.no {
  background-color: var(--error);
  color: var(--text-white);
}

.self-btn.no:hover {
  background-color: #9d1c1c;
}

/* Quiz Navigation */
.q-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px solid rgba(0, 0, 0, 0.1);
}
body.dark-mode .q-nav {
  border-top-color: rgba(255, 255, 255, 0.1);
}

.q-nav-btn {
  padding: 10px 20px;
  font-size: 0.85rem;
  font-weight: 700;
  font-family: var(--font);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  background-color: var(--bg-card);
  color: var(--text-main);
  transition: var(--transition);
}

.q-nav-btn:hover:not(:disabled) {
  background-color: var(--bg-tab-hover);
  border-color: var(--border-focus);
}

.q-nav-btn:disabled {
  opacity: 0.35;
  cursor: default;
}

.q-score {
  font-size: 0.8rem;
  background-color: var(--bg-nav);
  color: var(--text-main);
  padding: 6px 16px;
  border-radius: 50px;
  font-weight: 700;
}

/* Result Screen */
.result-wrap {
  text-align: center;
  padding: 40px 20px;
}

.result-wrap h3 {
  font-size: 1.4rem;
  font-weight: 800;
  margin-bottom: 8px;
}

.result-score {
  font-size: 3.5rem;
  font-weight: 900;
  color: var(--success);
  margin: 16px 0;
  text-shadow: 0 4px 10px rgba(46, 125, 50, 0.15);
}

.result-msg {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-bottom: 30px;
}

.restart-btn {
  padding: 12px 28px;
  font-size: 0.9rem;
  font-weight: 700;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  background-color: var(--bg-card);
  color: var(--text-main);
  transition: var(--transition);
  font-family: var(--font);
}

.restart-btn:hover {
  background-color: var(--bg-tab-hover);
  transform: translateY(-1px);
}

.next-step-btn {
  padding: 12px 28px;
  font-size: 0.9rem;
  font-weight: 700;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  background-color: var(--bg-header);
  color: var(--text-white);
  margin-left: 10px;
  transition: var(--transition);
  font-family: var(--font);
}

.next-step-btn:hover {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
}

/* Diagrams Tab */
.panel-d {
  background-color: var(--d-bg);
  border-radius: var(--radius-lg);
  padding: 20px;
  border: 1px solid rgba(239, 159, 39, 0.2);
}

.d-grid {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.d-card {
  background-color: var(--bg-card);
  border: 1px solid var(--d-card-border);
  border-radius: var(--radius-md);
  padding: 20px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.d-card:hover {
  box-shadow: var(--shadow-md);
}

.d-lbl {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--d-lbl-text);
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.d-lbl::before {
  content: '';
  width: 4px;
  height: 12px;
  background-color: var(--d-card-border);
  border-radius: var(--radius-sm);
}

.d-desc {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 12px;
  font-style: italic;
  line-height: 1.5;
}

.d-card svg {
  display: block;
  margin: 0 auto;
  max-width: 100%;
  height: auto;
}

/* Mobile & Platform Specific Tweaks */
@media (max-width: 768px) {
  .container {
    margin: 1rem auto;
    padding: 0 12px;
  }
  
  .card {
    padding: 16px;
  }
  
  .c-h1 {
    font-size: 1.35rem;
  }
  
  .c-grid {
    grid-template-columns: 1fr;
  }
  
  .tab-btn {
    padding: 12px 14px;
    font-size: 0.85rem;
  }
  
  .q-card {
    padding: 16px;
  }
  
  
  .q-txt {
    font-size: 0.95rem;
  }
  
  .q-opt {
    padding: 12px 16px;
    font-size: 0.85rem;
  }
  
  .result-score {
    font-size: 2.8rem;
  }
  
  .restart-btn, .next-step-btn {
    padding: 10px 18px;
    font-size: 0.8rem;
  }
  
  .self-check-wrap {
    flex-direction: row;
  }
}

/* iOS Safe Areas */
@supports (padding-bottom: env(safe-area-inset-bottom)) {
  .container {
    padding-bottom: calc(80px + env(safe-area-inset-bottom));
  }
}

/* ==========================================
   TTS 플레이어 스타일링
   ========================================== */
.tts-card {
  background: rgba(255, 255, 255, 0.85);
  border: 1px solid var(--border-color);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: var(--transition);
}
body.dark-mode .tts-card {
  background: rgba(30, 41, 59, 0.8);
}

.tts-container {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.tts-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px;
}

.tts-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--primary);
  display: flex;
  align-items: center;
  gap: 4px;
}

.tts-controls {
  display: flex;
  gap: 6px;
}

.tts-btn {
  padding: 6px 12px;
  font-size: 0.8rem;
  font-weight: 600;
  font-family: var(--font);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background-color: var(--bg-main);
  color: var(--text-main);
  cursor: pointer;
  transition: var(--transition);
}

.tts-btn:hover:not(:disabled) {
  background-color: var(--bg-tab-hover);
  border-color: var(--border-focus);
}

.tts-btn:disabled {
  opacity: 0.5;
  cursor: default;
}

#tts-play-btn {
  background-color: var(--primary);
  color: var(--text-white);
  border-color: var(--primary);
}
#tts-play-btn:hover:not(:disabled) {
  background-color: var(--primary-hover);
  border-color: var(--primary-hover);
}

.tts-select-group {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.8rem;
  font-weight: 600;
}

.tts-select-group select {
  padding: 4px 8px;
  font-size: 0.8rem;
  font-family: var(--font);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background-color: var(--bg-card);
  color: var(--text-main);
  outline: none;
  cursor: pointer;
  max-width: 180px;
}

/* 텍스트 낭독 하이라이트 효과 */
.tts-highlight {
  background-color: rgba(251, 191, 36, 0.2);
  border-radius: 4px;
  padding: 0 4px;
  box-shadow: 0 0 8px rgba(251, 191, 36, 0.15);
  transition: background-color 0.3s ease, box-shadow 0.3s ease;
}
body.dark-mode .tts-highlight {
  background-color: rgba(245, 158, 11, 0.25);
  box-shadow: 0 0 8px rgba(245, 158, 11, 0.2);
}

/* ==========================================================================
   주관식 다중 입력 & 격려 피드백 토스트 & 설명 요구(질문) UI 스타일
   ========================================================================== */

/* 다중 입력 수직 컨테이너 */
.q-sub-inputs-container {
  display: flex;
  flex-direction: column;
  gap: 10px;
  width: 100%;
  margin-bottom: 12px;
}

/* 다중 입력 행 */
.q-sub-input-row {
  display: flex;
  align-items: center;
  gap: 12px;
  background-color: var(--q-opt-bg);
  border: 1.5px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 10px 16px;
  transition: var(--transition);
}

.q-sub-input-row.has-text {
  flex-direction: column;
  align-items: flex-start;
  gap: 10px;
  padding: 14px 18px;
}

.sub-q-text {
  font-size: 0.95rem;
  font-weight: 500;
  line-height: 1.7;
  color: var(--text-main);
  word-break: keep-all;
  width: 100%;
}

.sub-q-controls {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  width: 100%;
}

.q-sub-input-row:focus-within {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(55, 138, 221, 0.15);
}

.q-sub-input-row .sub-num {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--primary);
  min-width: 24px;
  display: inline-block;
}

.q-sub-input-row .q-sub-input {
  flex: 1;
  padding: 8px 12px;
  font-size: 0.95rem;
  font-family: var(--font);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background-color: var(--bg-card);
  color: var(--text-main);
  outline: none;
  transition: var(--transition);
}

.q-sub-input-row .q-sub-input:focus {
  border-color: var(--border-focus);
}

/* 정오답 피드백에 따른 입력 행 스타일 */
.q-sub-input-row.sub-row-correct {
  border-color: var(--success-border);
  background-color: var(--success-bg);
}

.q-sub-input-row.sub-row-wrong {
  border-color: var(--error-border);
  background-color: var(--error-bg);
}

.q-sub-input-row .sub-correct-badge {
  font-size: 0.85rem;
  color: var(--text-muted);
  white-space: nowrap;
}

.q-sub-input-row.sub-row-correct .sub-correct-badge {
  color: var(--success);
}

.q-sub-input-row.sub-row-wrong .sub-correct-badge {
  color: var(--error);
}

.q-sub-input-row .sub-correct-badge strong {
  margin-left: 4px;
  font-weight: 700;
  background-color: var(--bg-card);
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid var(--border-color);
}

/* 격려 피드백 토스트 */
#praise-toast-container {
  position: fixed;
  bottom: 8%;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1100;
  display: flex;
  flex-direction: column;
  gap: 10px;
  pointer-events: none;
}

.praise-toast {
  background: rgba(12, 68, 124, 0.92);
  color: #ffffff;
  padding: 14px 28px;
  border-radius: 50px;
  font-weight: 700;
  font-size: 1.05rem;
  box-shadow: 0 10px 25px rgba(12, 68, 124, 0.2);
  border: 1px solid rgba(255, 255, 255, 0.15);
  opacity: 0;
  transform: translateY(20px) scale(0.9);
  transition: opacity 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275), 
              transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  pointer-events: none;
  white-space: nowrap;
}

body.dark-mode .praise-toast {
  background: rgba(56, 189, 248, 0.95);
  color: #0f172a;
  box-shadow: 0 10px 25px rgba(56, 189, 248, 0.25);
  border: 1px solid rgba(15, 23, 42, 0.15);
}

.praise-toast.show {
  opacity: 1;
  transform: translateY(0) scale(1);
}

/* 설명 요구(질문) 섹션 */
.explanation-request-section {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px dashed var(--border-color);
}

/* 질문·답변 기록 (2026-09-30) */
.qa-item {
  margin-bottom: 14px;
}

.qa-question {
  padding: 10px 14px;
  border-radius: var(--radius-md);
  background-color: var(--bg-main, rgba(127, 127, 127, 0.06));
  border: 1px solid var(--border-color);
}

.qa-question-label {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--secondary);
}

.qa-question-text {
  margin-top: 4px;
  font-size: 0.9rem;
  line-height: 1.6;
  color: var(--text-main);
  white-space: pre-line;
}

/* 피드백 상자의 strong은 한 줄 제목용(display:block)이라, 답변 속 굵은 글씨는 줄바꿈 없이 보이게 되돌린다 */
.q-fb .admin-response-content strong {
  display: inline;
  margin: 0;
}

.qa-others-btn {
  margin-top: 12px;
  background: none;
  border: none;
  padding: 4px 0;
  color: var(--text-muted);
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: underline;
  cursor: pointer;
  font-family: var(--font);
}

.qa-others-title {
  margin: 14px 0 8px;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-muted);
}

.request-explanation-btn {
  background-color: transparent;
  border: 1.5px solid var(--border-focus);
  color: var(--secondary);
  font-weight: 700;
  padding: 8px 16px;
  font-size: 0.85rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font);
  transition: var(--transition);
}

.request-explanation-btn:hover {
  background-color: var(--c-badge-bg);
  transform: translateY(-1px);
}

.explanation-form {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-top: 10px;
  animation: slideDown 0.3s ease;
}

.explanation-form.hidden {
  display: none;
}

.explanation-form textarea {
  width: 100%;
  min-height: 70px;
  padding: 10px 12px;
  font-size: 0.9rem;
  font-family: var(--font);
  border: 1.5px solid var(--border-color);
  border-radius: var(--radius-sm);
  background-color: var(--bg-card);
  color: var(--text-main);
  resize: vertical;
  outline: none;
  transition: var(--transition);
}

.explanation-form textarea:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(55, 138, 221, 0.1);
}

.explanation-form-buttons {
  display: flex;
  gap: 8px;
  justify-content: flex-end;
}

.explanation-send-btn {
  background-color: var(--bg-header);
  color: #ffffff;
  border: none;
  font-weight: 700;
  padding: 7px 14px;
  font-size: 0.8rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  font-family: var(--font);
}

body.dark-mode .explanation-send-btn {
  background-color: var(--primary);
  color: #0f172a;
}

.explanation-send-btn:hover {
  opacity: 0.9;
  transform: translateY(-1px);
}

.explanation-cancel-btn {
  background-color: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-main);
  font-weight: 600;
  padding: 7px 14px;
  font-size: 0.8rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  font-family: var(--font);
}

.explanation-cancel-btn:hover {
  background-color: var(--bg-tab-hover);
}

/* 대기 배지 */
.status-badge {
  display: inline-flex;
  align-items: center;
  font-size: 0.8rem;
  font-weight: 700;
  padding: 4px 10px;
  border-radius: 4px;
  color: #854f0b;
  background-color: #fef3c7;
  border: 1px solid #fde68a;
}

body.dark-mode .status-badge {
  color: #fef08a;
  background-color: #78350f;
  border: 1px solid #a16207;
}

.status-badge.error {
  color: var(--error);
  background-color: var(--error-bg);
  border-color: var(--error-border);
}

/* 정답/해설 — 비회원 회원가입 유도 게이트 */
.answer-gate-box {
  margin-top: 8px;
  padding: 18px 20px;
  border-radius: var(--radius-sm);
  background-color: var(--c-tip-bg);
  border: 1.5px dashed var(--c-tip-border);
  text-align: center;
}

.answer-gate-icon {
  font-size: 1.4rem;
  margin-bottom: 6px;
}

.answer-gate-text {
  font-size: 0.85rem;
  line-height: 1.65;
  color: var(--c-tip-text);
  margin-bottom: 14px;
}

.answer-gate-btn {
  display: inline-block;
  background-color: var(--primary);
  color: #ffffff;
  font-weight: 700;
  padding: 10px 20px;
  font-size: 0.85rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  font-family: var(--font);
  transition: var(--transition);
}

.answer-gate-btn:hover {
  opacity: 0.9;
  transform: translateY(-1px);
}

/* 문항 네비게이터 그리드 */
.q-grid-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 12px;
  border-radius: var(--radius-md);
  justify-content: flex-start;
}

.q-grid-item {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  border: 1.5px solid var(--border-color);
  background-color: var(--bg-main);
  color: var(--text-main);
  font-size: 0.85rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
  font-family: var(--font);
}

.q-grid-item:hover {
  border-color: var(--border-focus);
  transform: translateY(-1px);
}

.q-grid-item.active {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(55, 138, 221, 0.25);
  background-color: var(--border-focus);
  color: #ffffff;
}

body.dark-mode .q-grid-item.active {
  background-color: var(--primary);
  color: #0f172a;
}

.q-grid-item.correct {
  background-color: var(--success);
  border-color: var(--success);
  color: #ffffff;
}

.q-grid-item.wrong {
  background-color: var(--error);
  border-color: var(--error);
  color: #ffffff;
}

.q-grid-item.pending-eval {
  background-color: #d97706; /* Amber color */
  border-color: #d97706;
  color: #ffffff;
}

/* 터치식 서브 선택 단추 */
.sub-choice-buttons {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.sub-choice-btn {
  padding: 6px 16px;
  font-size: 0.85rem;
  font-weight: 700;
  font-family: var(--font);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background-color: var(--bg-card);
  color: var(--text-main);
  cursor: pointer;
  transition: var(--transition);
}

.sub-choice-btn:hover:not(:disabled) {
  border-color: var(--border-focus);
  background-color: var(--bg-tab-hover);
}

.sub-choice-btn.active {
  background-color: var(--border-focus);
  border-color: var(--border-focus);
  color: #ffffff;
}

body.dark-mode .sub-choice-btn.active {
  background-color: var(--primary);
  color: #0f172a;
}

.sub-choice-btn:disabled {
  cursor: default;
  opacity: 0.85;
}

/* ==========================================
   Responsive Multi-level Sidebar Styles
   ========================================== */

/* Menu toggle button in header */
.menu-toggle-btn {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-white);
  padding: 8px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
  font-size: 1.25rem;
  margin-right: 8px;
}

.menu-toggle-btn:hover {
  background-color: rgba(255, 255, 255, 0.15);
}

/* App layout container */
.app-layout {
  display: flex;
  min-height: calc(100vh - 61px);
  position: relative;
}

/* Backdrop overlay on mobile */
.sidebar-backdrop {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(2px);
  z-index: 150;
  opacity: 0;
  transition: opacity 0.3s ease;
  pointer-events: none;
}

.sidebar-backdrop.active {
  display: block;
  opacity: 1;
  pointer-events: auto;
}

/* Sidebar aside element */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 280px;
  height: 100vh;
  background-color: var(--bg-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  z-index: 200;
  transform: translateX(-100%);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: var(--shadow-lg);
}

.sidebar.active {
  transform: translateX(0);
}

/* Sidebar header */
.sidebar-header {
  padding: 16px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border-color);
}

.sidebar-header h2 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.01em;
}

.sidebar-close-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.5rem;
  cursor: pointer;
  padding: 4px 8px;
  line-height: 1;
  transition: var(--transition);
}

.sidebar-close-btn:hover {
  color: var(--text-main);
}

/* Sidebar scrollable links container */
.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 16px 12px;
}

/* Multi-level Hierarchy styling */
.nav-group {
  margin-bottom: 12px;
}

.nav-group-title {
  display: flex;
  align-items: center;
  width: 100%;
  padding: 10px 12px;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--text-main);
  background: none;
  border: none;
  text-align: left;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.nav-group-title:hover {
  background-color: var(--bg-tab-hover);
}

.nav-group-title .nav-group-prefix {
  color: var(--primary);
  margin-right: 6px;
  min-width: 18px;
  display: inline-block;
}

body.dark-mode .nav-group-title .nav-group-prefix {
  color: var(--primary-hover);
}

.nav-group-title .nav-group-text {
  flex: 1;
}

.nav-group-title .chevron,
.nav-subgroup-title .chevron {
  font-size: 0.75rem;
  color: var(--text-muted);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  margin-left: auto;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 16px;
  height: 16px;
}

.nav-group-title.expanded .chevron,
.nav-subgroup-title.expanded .chevron {
  transform: rotate(90deg);
}

.nav-group-content {
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  padding-left: 12px;
  transition: max-height 0.3s ease, opacity 0.2s ease, padding 0.3s ease;
}

.nav-group-content.expanded {
  max-height: 1000px;
  opacity: 1;
  padding-top: 4px;
  padding-bottom: 4px;
}

/* Sub-group (level 2) collapsible */
.nav-subgroup {
  margin: 4px 0;
}

.nav-subgroup-title {
  display: flex;
  align-items: center;
  width: 100%;
  padding: 8px 12px; /* Matched to nav-item padding for pixel-perfect vertical alignment */
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-main);
  background: none;
  border: none;
  text-align: left;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.nav-subgroup-title:hover {
  background-color: var(--bg-tab-hover);
}

.nav-subgroup-title .nav-item-prefix {
  color: var(--secondary);
  margin-right: 8px;
  min-width: 24px;
  display: inline-block;
  font-weight: 700;
}

.nav-subgroup-title .nav-item-text {
  flex: 1;
}

.nav-subgroup-content {
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  padding-left: 12px;
  transition: max-height 0.3s ease, opacity 0.2s ease, padding 0.3s ease;
}

.nav-subgroup-content.expanded {
  max-height: 500px;
  opacity: 1;
  padding-top: 2px;
  padding-bottom: 2px;
}

/* Sidebar leaf link items */
.nav-item {
  display: flex !important;
  align-items: center;
  padding: 8px 12px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  border-radius: var(--radius-sm);
  transition: var(--transition);
  margin: 2px 0;
  cursor: pointer;
}

.nav-item:hover {
  color: var(--text-main);
  background-color: var(--bg-tab-hover);
}

.nav-item.active {
  color: var(--primary);
  background-color: var(--c-badge-bg);
  font-weight: 700;
}

body.dark-mode .nav-item.active {
  color: var(--primary);
  background-color: var(--bg-tab-hover);
}

.nav-item .nav-item-prefix {
  color: var(--text-muted);
  margin-right: 8px;
  min-width: 24px;
  display: inline-block;
  font-weight: 600;
  transition: var(--transition);
}

.nav-item.active .nav-item-prefix {
  color: var(--primary);
  font-weight: 700;
}

body.dark-mode .nav-item.active .nav-item-prefix {
  color: var(--primary);
}

.nav-item .nav-item-prefix.empty {
  min-width: 24px;
}

.nav-item .nav-item-text {
  flex: 1;
}

/* Main Content column adjustment */
.main-content {
  flex: 1;
  min-width: 0;
  transition: padding-left 0.3s ease;
}

/* Desktop and Tablet layout rules: When screen size is larger than 767px */
@media (min-width: 768px) {
  .menu-toggle-btn {
    display: none !important; /* Hide toggle menu button */
  }
  
  .sidebar-backdrop {
    display: none !important;
  }
  
  .sidebar {
    position: sticky;
    top: 61px; /* Sticky below header */
    height: calc(100vh - 61px);
    transform: none; /* Always visible */
    box-shadow: none;
    z-index: 10;
  }
  
  .sidebar-close-btn {
    display: none; /* Hide close button */
  }
}

/* ==========================================
   🔍 작품 감상 돋보기 모달 및 다운로드 버튼 스타일
   ========================================== */
.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(15, 23, 42, 0.45);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.modal.show {
  display: flex;
  opacity: 1;
}

.modal-content {
  background: var(--c-card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  max-width: 700px;
  width: 92%;
  max-height: 85vh;
  overflow-y: auto;
  padding: 25px 30px 30px;
  box-shadow: var(--shadow-lg);
  transform: scale(0.95);
  transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  position: relative;
}

.modal.show .modal-content {
  transform: scale(1);
}

.modal-close {
  position: absolute;
  top: 18px;
  right: 18px;
  background: rgba(0, 0, 0, 0.05);
  border: none;
  border-radius: 50%;
  width: 32px;
  height: 32px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  color: var(--text-main);
  transition: var(--transition);
  z-index: 10;
}

.modal-close:hover {
  background: rgba(239, 68, 68, 0.1);
  color: var(--error);
}

/* 다크모드 대응 닫기 버튼 */
body.dark-mode .modal-close {
  background: rgba(255, 255, 255, 0.1);
}
body.dark-mode .modal-close:hover {
  background: rgba(239, 68, 68, 0.2);
}

/* 📥 다운로드 버튼 */
.modal-download-btn {
  background-color: var(--secondary);
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  padding: 6px 12px;
  font-size: 0.75rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
}

.modal-download-btn:hover {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
}

/* 🔍 작품 보기 돋보기용 본문 호출 버튼 */
.c-btn-open-work {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background-color: var(--c-badge-bg);
  color: var(--c-badge-text);
  border: 1px solid var(--border-color);
  border-radius: 30px;
  padding: 8px 16px;
  font-size: 0.8rem;
  font-weight: 700;
  cursor: pointer;
  margin: 10px 0;
  transition: var(--transition);
}

.c-btn-open-work:hover {
  background-color: var(--bg-tab-hover);
  border-color: var(--border-focus);
  transform: translateY(-1px);
}

/* 아코디언 스타일 (Alternative 2) */
.c-details {
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background-color: var(--c-card-bg);
  margin: 15px 0;
  overflow: hidden;
  transition: var(--transition);
}

.c-details[open] {
  box-shadow: var(--shadow-sm);
  border-color: var(--border-focus);
}

.c-summary {
  padding: 12px 18px;
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--primary);
  cursor: pointer;
  background-color: var(--bg-main);
  outline: none;
  user-select: none;
  transition: var(--transition);
}

.c-summary:hover {
  background-color: var(--bg-tab-hover);
}

.c-details-content {
  padding: 16px 20px;
  border-top: 1px solid var(--border-color);
  font-size: 0.85rem;
  line-height: 1.8;
  color: var(--text-main);
}

/* ==========================================
   문항 네비게이터 사이드바 배치 스타일
   ========================================== */

/* 사이드바 내 문항 번호 그리드 */
.sidebar-grid-nav {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
  padding: 12px;
  background-color: var(--bg-main);
  border: 1.5px solid var(--border-color);
  border-radius: var(--radius-md);
  margin-bottom: 15px;
}

body.dark-mode .sidebar-grid-nav {
  background-color: rgba(0, 0, 0, 0.2);
}

.sidebar-grid-nav .q-grid-item {
  width: 100%;
  height: auto;
  aspect-ratio: 1 / 1;
  border-radius: 50%;
  font-size: 0.8rem;
}

/* 프리미엄 개념 학습 이미지 래퍼 및 캡션 */
.concept-image-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 28px auto;
  max-width: 85%;
  padding: 14px;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  transition: box-shadow 0.3s ease;
}
body.dark-mode .concept-image-wrap {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
  background-color: rgba(255, 255, 255, 0.02);
}
.concept-img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}
.concept-image-wrap:hover {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
}
body.dark-mode .concept-image-wrap:hover {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
}
.concept-img:hover {
  transform: scale(1.015);
}
.concept-img-caption {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-weight: 600;
  margin-top: 10px;
  text-align: center;
}

/* 데스크톱(화면 가로 768px 이상)에서 본문 영역 상단 문항 네비게이터 숨김 */
@media (min-width: 768px) {
  .main-content .q-grid-nav {
    display: none !important;
  }
}

/* ==========================================
   premium 개념학습 본문 가독성 스타일
   ========================================== */
.concept-container {
  max-width: 860px;
  margin: 0 auto;
  padding: 30px 24px;
  line-height: 1.8;
  font-family: var(--font);
  color: var(--text-main);
  background-color: var(--c-card-bg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
}

body.dark-mode .concept-container {
  background-color: var(--bg-card);
}

.concept-section-title {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--primary);
  margin-top: 50px;
  margin-bottom: 22px;
  padding-bottom: 12px;
  border-bottom: 3px solid var(--primary);
  letter-spacing: -0.025em;
}
body.dark-mode .concept-section-title {
  color: var(--primary-hover);
  border-bottom-color: var(--primary-hover);
}

.concept-subsection-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--secondary);
  margin-top: 38px;
  margin-bottom: 18px;
  padding: 8px 14px;
  background-color: var(--bg-nav);
  border-left: 5px solid var(--secondary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  letter-spacing: -0.015em;
}
body.dark-mode .concept-subsection-title {
  background-color: rgba(55, 138, 221, 0.1);
  color: var(--primary);
}

.concept-topic-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  margin-top: 28px;
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 10px;
  padding-bottom: 6px;
  border-bottom: 1.5px dashed var(--border-color);
  letter-spacing: -0.01em;
}
.concept-topic-title::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--secondary);
}

.concept-subtopic-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-muted);
  margin-top: 24px;
  margin-bottom: 12px;
  padding-left: 14px;
  position: relative;
  letter-spacing: -0.005em;
}
.concept-subtopic-title::before {
  content: "▪";
  position: absolute;
  left: 0;
  color: var(--secondary);
  font-size: 0.95rem;
  line-height: 1;
  top: 2px;
}


.concept-text {
  font-size: 1.05rem;
  font-weight: 400;
  line-height: 1.7;
  margin-bottom: 22px;
  text-align: left;
  word-break: keep-all;
  overflow-wrap: break-word;
  letter-spacing: -0.02em;
}

/* 글머리 기호나 번호 리스트 가독성 */
.concept-text.list-item {
  padding-left: 20px;
  text-indent: -20px;
  margin-bottom: 12px;
}

.concept-text.list-sub-item {
  padding-left: 40px;
  text-indent: -20px;
  margin-bottom: 12px;
}

.concept-grid-4col {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px 16px;
  margin: 15px 0 25px 20px;
  font-size: 0.95rem;
}
@media (max-width: 600px) {
  .concept-grid-4col {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* 각주 스타일 */
.concept-footnote {
  font-size: 0.88rem;
  color: var(--text-muted);
  background-color: var(--bg-main);
  padding: 14px 18px;
  border-left: 3px solid var(--border-color);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 20px 0;
  line-height: 1.6;
}
body.dark-mode .concept-footnote {
  background-color: rgba(255, 255, 255, 0.02);
}

/* 참고/핵심 팁 박스 */
.concept-tip-box {
  background-color: var(--c-tip-bg);
  border: 1px solid var(--c-tip-border);
  border-radius: var(--radius-md);
  padding: 20px;
  margin: 25px 0;
  color: var(--c-tip-text);
}
.concept-tip-box h5 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--primary);
}

/* 개념 표 스타일 */
.concept-table-wrapper {
  overflow-x: auto;
  margin: 25px 0;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
}
.concept-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}
.concept-table th {
  background-color: var(--c-tbl-th);
  color: var(--primary);
  font-weight: 700;
  padding: 14px 16px;
  border-bottom: 2px solid var(--border-color);
  letter-spacing: -0.01em;
}
body.dark-mode .concept-table th {
  background-color: var(--bg-nav);
  color: var(--primary);
  border-bottom-color: var(--border-color);
}
.concept-table td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-main);
}
.concept-table td,
.concept-table th {
  /* Keep Korean words/phrases intact when a cell must wrap, instead of
     breaking mid-syllable between any two Hangul characters (e.g. a
     "구체 → 구" / "체" style split). */
  word-break: keep-all;
}
.concept-table td:first-child,
.concept-table th:first-child {
  /* First column is almost always a short category/label cell; keep it
     on one line so it never wraps at all. Tables where column 1 holds
     genuinely long, sentence-like content opt out via .wide-first-col
     (see below) so that content keeps wrapping normally. */
  white-space: nowrap;
}
.concept-table.wide-first-col td:first-child,
.concept-table.wide-first-col th:first-child {
  white-space: normal;
}
.concept-table-scroll {
  /* Most concept tables in the site content are NOT wrapped in
     .concept-table-wrapper, and body has overflow-x:hidden — so a table
     that grows wider than its column (e.g. from the first-column nowrap
     rule above, or simply long "예시" content) would otherwise be
     silently clipped and unreachable instead of scrollable. This wrapper
     is purely functional (no border/shadow/margin) and is only added,
     by the build, around tables that don't already have
     .concept-table-wrapper. */
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.concept-table tr:last-child td {
  border-bottom: none;
}
.concept-table tr:nth-child(even) {
  background-color: var(--c-tbl-tr-even);
}
body.dark-mode .concept-table tr:nth-child(even) {
  background-color: rgba(255, 255, 255, 0.02);
}
.concept-table tr:hover {
  background-color: var(--bg-nav);
  transition: var(--transition);
}
body.dark-mode .concept-table tr:hover {
  background-color: rgba(255, 255, 255, 0.04);
}
.concept-table .text-center {
  text-align: center;
}
.concept-table .text-right {
  text-align: right;
}
.concept-table-caption {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--primary);
  margin-top: 25px;
  margin-bottom: 8px;
  text-align: center;
}
body.dark-mode .concept-table-caption {
  color: var(--primary-hover);
}
.concept-table-source {
  font-size: 0.82rem;
  color: var(--text-muted);
  text-align: center;
  margin-top: 6px;
  margin-bottom: 25px;
}

/* 위계도/포함관계 다이어그램형 표 (예: "논리적 사고 ⊃ 창의적 사고" 처럼
   colspan으로 폭이 점점 좁아지는 밴드를 쌓아 표현하는 표) 전용 색상 단계.
   행(tr)에 diagram-tint-1~4 클래스를 주면 단계가 깊어질수록(폭이 좁아질수록)
   진한 색으로 강조되어, 표 없이 이미지로만 보던 위계 구조를 표로도
   한눈에 알아볼 수 있게 한다. */
.concept-table tr.diagram-tint-1 th,
.concept-table tr.diagram-tint-1 td {
  background-color: var(--c-tbl-th);
  text-align: center;
  font-weight: 700;
  color: var(--primary);
}
.concept-table tr.diagram-tint-2 td {
  background-color: rgba(55, 138, 221, 0.16);
  text-align: center;
  font-weight: 600;
  color: var(--primary);
}
.concept-table tr.diagram-tint-3 td {
  background-color: rgba(55, 138, 221, 0.28);
  text-align: center;
  font-weight: 600;
  color: var(--primary);
}
.concept-table tr.diagram-tint-4 td {
  background-color: rgba(55, 138, 221, 0.42);
  text-align: center;
  font-weight: 700;
  color: var(--primary);
}
body.dark-mode .concept-table tr.diagram-tint-2 td {
  background-color: rgba(14, 165, 233, 0.16);
}
body.dark-mode .concept-table tr.diagram-tint-3 td {
  background-color: rgba(14, 165, 233, 0.26);
}
body.dark-mode .concept-table tr.diagram-tint-4 td {
  background-color: rgba(14, 165, 233, 0.38);
}

/* Sidebar Sub-items Styling */
.nav-sub-items-container {
  padding-left: 14px;
  margin: 6px 0 8px 12px;
  border-left: 1px dashed var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-sub-item {
  display: flex !important;
  align-items: flex-start;
  gap: 6px;
  padding: 4px 0;
  font-size: 0.82rem;
  color: var(--text-main);
  text-decoration: none;
  cursor: pointer;
  line-height: 1.4;
  opacity: 0.85;
  transition: var(--transition);
}

.nav-sub-item::before {
  content: "•";
  color: var(--text-muted);
  flex-shrink: 0;
  font-size: 0.82rem;
  line-height: 1.4;
}

.nav-sub-item:hover {
  color: var(--secondary) !important;
  opacity: 1 !important;
  transform: translateX(3px);
}

.nav-sub-item.level-5 {
  padding-left: 12px;
  font-size: 0.78rem;
  opacity: 0.7;
}

.nav-sub-item.level-5::before {
  content: "◦";
  font-size: 0.78rem;
}