/* ========== PE Civil 학습 사이트 · 공통 스타일 ========== */

/* Pretendard — 모던 한글 산세리프 */
@import url('https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/variable/pretendardvariable-dynamic-subset.min.css');

:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --surface-2: #fafbfc;
  --border: #e3e7ec;
  --border-2: #f1f5f9;
  --text: #1f2937;
  --text-2: #374151;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-soft: #eff6ff;
  --success: #059669;
  --success-soft: #ecfdf5;
  --warn: #d97706;
  --warn-soft: #fffbeb;
  --danger: #dc2626;
  --danger-soft: #fef2f2;
  --math-bg: #f8fafc;
  --math-border: #dbeafe;

  --accent-1: #2563eb;  /* Construction */
  --accent-2: #7c3aed;  /* Geotechnics */
  --accent-3: #059669;  /* Structures */
  --accent-4: #0891b2;  /* Water & Env */
  --accent-5: #db2777;  /* Transportation */
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 80px; }

body {
  margin: 0;
  font-family: 'Pretendard Variable', Pretendard, -apple-system, BlinkMacSystemFont,
               system-ui, 'Segoe UI', 'Apple SD Gothic Neo', 'Noto Sans KR',
               'Malgun Gothic', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 15.5px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  letter-spacing: -0.01em;
}

h1, h2, h3, h4 { letter-spacing: -0.02em; }

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ========== 상단 네비게이션 ========== */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.nav-brand {
  font-weight: 700;
  font-size: 16px;
  color: var(--text);
  letter-spacing: -0.3px;
  white-space: nowrap;
}
.nav-brand:hover { text-decoration: none; }
.nav-links {
  display: flex;
  gap: 4px;
  align-items: center;
  flex-wrap: wrap;
}
.nav-link {
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 14px;
  color: var(--muted);
  font-weight: 500;
  transition: all 0.15s;
}
.nav-link:hover { background: var(--primary-soft); color: var(--primary); text-decoration: none; }
.nav-link.active { background: var(--primary); color: white; }

/* ========== 브레드크럼 ========== */
.breadcrumb {
  max-width: 1100px;
  margin: 16px auto 0;
  padding: 0 20px;
  font-size: 13px;
  color: var(--muted);
}
.breadcrumb a { color: var(--muted); }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb .sep { margin: 0 6px; opacity: 0.5; }

/* ========== 히어로 ========== */
.hero {
  background: linear-gradient(135deg, #1e3a8a, #7c3aed);
  color: white;
  padding: 56px 24px 64px;
  text-align: center;
}
.hero.compact { padding: 32px 24px 36px; }
.hero h1 { margin: 0 0 10px; font-size: 30px; font-weight: 700; letter-spacing: -0.5px; }
.hero.compact h1 { font-size: 24px; }
.hero p { margin: 0; opacity: 0.9; font-size: 15px; }

/* 토픽별 헤더 그라디언트 */
.hero-t1 { background: linear-gradient(135deg, #1e3a8a, #2563eb); }
.hero-t2 { background: linear-gradient(135deg, #4c1d95, #7c3aed); }
.hero-t3 { background: linear-gradient(135deg, #064e3b, #059669); }
.hero-t4 { background: linear-gradient(135deg, #0c4a6e, #0891b2); }
.hero-t5 { background: linear-gradient(135deg, #831843, #db2777); }

/* ========== 메인 레이아웃 ========== */
main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 24px 20px 60px;
}
main.narrow { max-width: 860px; }

.card {
  background: var(--surface);
  border-radius: 12px;
  box-shadow: 0 2px 10px rgba(15, 23, 42, 0.04);
  border: 1px solid var(--border);
  overflow: hidden;
}

/* ========== 토픽·모듈 카드 그리드 ========== */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 18px;
  margin-top: 8px;
}
.topic-card {
  display: block;
  padding: 22px 22px 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text);
  transition: all 0.2s;
  position: relative;
  overflow: hidden;
}
.topic-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 28px rgba(15, 23, 42, 0.1);
  text-decoration: none;
}
.topic-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: var(--accent);
}
.topic-card.t1 { --accent: var(--accent-1); }
.topic-card.t2 { --accent: var(--accent-2); }
.topic-card.t3 { --accent: var(--accent-3); }
.topic-card.t4 { --accent: var(--accent-4); }
.topic-card.t5 { --accent: var(--accent-5); }

.topic-card .icon { font-size: 32px; margin-bottom: 8px; }
.topic-card h3 { margin: 0 0 6px; font-size: 17px; font-weight: 700; }
.topic-card .meta {
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 10px;
}
.topic-card .desc { color: var(--text-2); font-size: 14px; margin: 0 0 14px; }

.topic-card .progress {
  height: 6px;
  background: var(--border-2);
  border-radius: 3px;
  overflow: hidden;
}
.topic-card .progress-fill {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width 0.4s;
}
.topic-card .progress-text {
  font-size: 11.5px;
  color: var(--muted);
  margin-top: 5px;
  font-weight: 500;
}

/* 모듈 카드 (Topic 랜딩용) */
.module-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 14px;
}
.module-card {
  display: block;
  padding: 18px 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--text);
  transition: all 0.15s;
}
.module-card:hover {
  border-color: var(--primary);
  box-shadow: 0 6px 18px rgba(37, 99, 235, 0.08);
  text-decoration: none;
}
.module-card .mid {
  font-size: 12px;
  font-weight: 700;
  color: var(--primary);
  letter-spacing: 0.8px;
}
.module-card h4 { margin: 2px 0 4px; font-size: 16px; font-weight: 700; }
.module-card .subtitle { color: var(--muted); font-size: 13px; margin: 0; }

/* ========== 문제 카드 ========== */
.section-title {
  font-size: 22px;
  font-weight: 700;
  margin: 40px 0 14px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.section-title:first-child { margin-top: 8px; }
.section-title .icon { font-size: 24px; }

.section-intro {
  color: var(--text-2);
  margin: -6px 0 20px;
  font-size: 15px;
}

.problem {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: 0 2px 10px rgba(15, 23, 42, 0.03);
  overflow: hidden;
  margin-bottom: 22px;
}
.problem-head {
  padding: 18px 26px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
  background: linear-gradient(180deg, #fafbfc, #fff);
}
.problem-head h3 { margin: 0; font-size: 18px; font-weight: 700; }
.problem-head .qtag {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  padding: 3px 10px;
  background: var(--border-2);
  border-radius: 999px;
  letter-spacing: 0.5px;
}
.problem-body { padding: 22px 26px; }

.question-text {
  font-size: 15.5px;
  background: #f8fafc;
  border-left: 4px solid var(--primary);
  padding: 14px 18px;
  border-radius: 4px;
  margin: 0 0 16px;
}

/* ========== 선택지 ========== */
.choices {
  list-style: none;
  padding: 0;
  margin: 0 0 18px;
  display: grid;
  gap: 8px;
}
.choice {
  display: flex;
  gap: 12px;
  padding: 12px 16px;
  border: 2px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.15s;
  background: white;
  align-items: flex-start;
}
.choice:hover { border-color: var(--primary); background: var(--primary-soft); }
.choice .letter {
  font-weight: 700;
  color: var(--primary);
  min-width: 20px;
}
.choice.selected { border-color: var(--primary); background: var(--primary-soft); }
.choice.correct { border-color: var(--success); background: var(--success-soft); }
.choice.correct .letter { color: var(--success); }
.choice.wrong { border-color: var(--danger); background: var(--danger-soft); }
.choice.wrong .letter { color: var(--danger); }

/* ========== 해설 ========== */
.reveal-btn {
  background: var(--primary);
  color: white;
  border: none;
  padding: 10px 22px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
  transition: background 0.15s;
}
.reveal-btn:hover { background: var(--primary-dark); }
.reveal-btn.ghost {
  background: transparent;
  color: var(--primary);
  border: 1.5px solid var(--primary);
}
.reveal-btn.ghost:hover { background: var(--primary-soft); }

.solution {
  display: none;
  margin-top: 22px;
  padding: 22px 26px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 10px;
}
.solution.shown { display: block; animation: fadeIn 0.3s; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(-4px); } to { opacity: 1; transform: translateY(0); } }

.solution h4 {
  margin: 0 0 14px;
  font-size: 16px;
  color: var(--success);
}

.step {
  margin: 20px 0 8px;
  padding: 6px 12px;
  background: #eef2ff;
  color: #3730a3;
  font-weight: 600;
  font-size: 14px;
  border-radius: 6px;
  display: inline-block;
}

/* 수식 카드 */
.eq-card {
  background: linear-gradient(180deg, #ffffff, var(--math-bg));
  border: 1px solid var(--math-border);
  border-left: 4px solid var(--primary);
  border-radius: 8px;
  padding: 14px 20px;
  margin: 10px 0 14px;
  overflow-x: auto;
}
.eq-key {
  background: linear-gradient(180deg, #fffbeb, #fef3c7);
  border: 1px solid #fcd34d;
  border-left: 4px solid var(--warn);
  border-radius: 8px;
  padding: 14px 20px;
  margin: 10px 0 14px;
  overflow-x: auto;
}
.eq-final {
  background: linear-gradient(180deg, #ecfdf5, #d1fae5);
  border: 1.5px solid #10b981;
  border-radius: 8px;
  padding: 16px 20px;
  margin: 14px 0;
  text-align: center;
  overflow-x: auto;
}
.eq-label {
  display: inline-block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.8px;
  color: var(--muted);
  text-transform: uppercase;
  margin-bottom: 6px;
}
.eq-key .eq-label { color: var(--warn); }
.eq-final .eq-label { color: var(--success); }

/* KaTeX 크기 조정 */
.katex-display { margin: 0.4em 0 !important; font-size: 1.15em; }
.katex { font-size: 1.05em; }
.eq-final .katex { font-size: 1.25em; }

.concept-box {
  background: var(--warn-soft);
  border-left: 4px solid var(--warn);
  padding: 14px 18px;
  border-radius: 4px;
  margin: 14px 0;
  font-size: 14.5px;
}
.concept-box strong { color: var(--warn); }
.concept-box.info { background: var(--primary-soft); border-left-color: var(--primary); }
.concept-box.info strong { color: var(--primary); }
.concept-box.note { background: #f0fdf4; border-left-color: var(--success); }
.concept-box.note strong { color: var(--success); }

.answer-reveal {
  display: block;
  padding: 12px 18px;
  background: linear-gradient(135deg, #ecfdf5, #d1fae5);
  color: var(--success);
  border-radius: 8px;
  font-weight: 700;
  font-size: 16px;
  margin-top: 18px;
  text-align: center;
  border: 1.5px solid #10b981;
}

/* ========== 다이어그램 ========== */
.diagram {
  background: white;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px;
  margin: 16px 0;
  text-align: center;
}
.diagram svg { max-width: 100%; height: auto; }
.diagram-caption {
  font-size: 12.5px;
  color: var(--muted);
  margin-top: 8px;
}

/* ========== 표 ========== */
.table-wrap { overflow-x: auto; margin: 10px 0 16px; }
table.data {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  background: white;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--border);
}
table.data th {
  background: #f1f5f9;
  color: var(--text-2);
  padding: 10px 14px;
  text-align: left;
  font-weight: 600;
  border-bottom: 1px solid var(--border);
}
table.data td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-2);
}
table.data tr:last-child td { border-bottom: none; }
table.data tr:nth-child(even) td { background: #fafbfc; }
table.data td.num { font-variant-numeric: tabular-nums; text-align: right; }

/* ========== 퀴즈 모드 ========== */
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 22px;
  background: linear-gradient(135deg, #1e3a8a, #2563eb);
  color: white;
  border-radius: 12px 12px 0 0;
  flex-wrap: wrap;
  gap: 14px;
}
.quiz-header h3 { margin: 0; font-size: 17px; }
.quiz-timer {
  font-family: 'JetBrains Mono', ui-monospace, Consolas, monospace;
  font-size: 22px;
  font-weight: 700;
  padding: 6px 14px;
  background: rgba(255, 255, 255, 0.2);
  border-radius: 6px;
  min-width: 100px;
  text-align: center;
}
.quiz-timer.warning { background: rgba(245, 158, 11, 0.3); }
.quiz-timer.danger { background: rgba(220, 38, 38, 0.4); animation: pulse 1s infinite; }
@keyframes pulse { 0%,100% { opacity:1 } 50% { opacity: 0.6 } }

.quiz-body { padding: 22px 26px; background: white; border-radius: 0 0 12px 12px; border: 1px solid var(--border); border-top: none; }

.quiz-q {
  padding: 18px 0;
  border-bottom: 1px solid var(--border-2);
}
.quiz-q:last-child { border-bottom: none; }
.quiz-q .qnum {
  display: inline-block;
  font-weight: 700;
  color: var(--primary);
  margin-right: 8px;
}

.quiz-submit {
  background: var(--success);
  color: white;
  border: none;
  padding: 12px 32px;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 700;
  cursor: pointer;
  font-family: inherit;
  margin-top: 24px;
  width: 100%;
  transition: background 0.15s;
}
.quiz-submit:hover { background: #047857; }
.quiz-submit:disabled { background: #9ca3af; cursor: not-allowed; }

.quiz-result {
  display: none;
  margin-top: 24px;
  padding: 20px 24px;
  background: linear-gradient(135deg, #ecfdf5, #d1fae5);
  border: 2px solid var(--success);
  border-radius: 10px;
}
.quiz-result.shown { display: block; }
.quiz-result h4 { margin: 0 0 8px; font-size: 20px; color: var(--success); }
.quiz-result .score { font-size: 32px; font-weight: 700; color: var(--success); }
.quiz-result p { margin: 4px 0; }

/* ========== 페이지 하단 네비게이션 ========== */
.page-nav {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  flex-wrap: wrap;
}
.page-nav a {
  flex: 1 1 200px;
  padding: 14px 18px;
  background: white;
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  transition: all 0.15s;
}
.page-nav a:hover { border-color: var(--primary); text-decoration: none; background: var(--primary-soft); }
.page-nav a .dir { font-size: 12px; color: var(--muted); font-weight: 600; }
.page-nav a .title { font-size: 15px; font-weight: 600; margin-top: 2px; }
.page-nav a.next { text-align: right; }
.page-nav a.prev::before { content: '← '; color: var(--muted); }
.page-nav a.next::after  { content: ' →'; color: var(--muted); }

/* ========== TOC (목차) ========== */
.toc {
  background: white;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px 18px;
  margin-bottom: 24px;
  font-size: 14px;
}
.toc-title {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: 0.6px;
  text-transform: uppercase;
  margin-bottom: 8px;
}
.toc ul { margin: 0; padding: 0 0 0 16px; }
.toc li { margin: 3px 0; }
.toc a { color: var(--text-2); }

/* ========== 푸터 ========== */
footer {
  text-align: center;
  padding: 32px 20px;
  color: var(--muted);
  font-size: 13px;
  border-top: 1px solid var(--border);
  margin-top: 40px;
}

/* ========== 대시보드 ========== */
.dashboard-card {
  background: linear-gradient(135deg, #1e3a8a 0%, #7c3aed 100%);
  color: white;
  border-radius: 14px;
  padding: 26px 28px;
  margin-bottom: 20px;
  box-shadow: 0 10px 28px rgba(30, 58, 138, 0.22);
}
.dashboard-card h3 {
  margin: 0 0 4px;
  font-size: 20px;
  color: white;
  display: flex;
  align-items: center;
  gap: 8px;
}
.dashboard-card .sub {
  margin: 0 0 18px;
  opacity: 0.85;
  font-size: 13.5px;
}
.dashboard-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 14px;
}
.stat-card {
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: 10px;
  padding: 14px 16px;
  text-align: center;
}
.stat-card .stat-num {
  font-size: 28px;
  font-weight: 800;
  letter-spacing: -0.5px;
  line-height: 1.1;
  color: white;
}
.stat-card .stat-lbl {
  font-size: 12px;
  opacity: 0.85;
  margin-top: 6px;
}
.dashboard-bar {
  height: 10px;
  background: rgba(255, 255, 255, 0.15);
  border-radius: 5px;
  overflow: hidden;
  margin-top: 16px;
}
.dashboard-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, #10b981, #60a5fa);
  width: 0%;
  transition: width 0.5s;
}
.dashboard-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 12px;
  font-size: 12px;
  opacity: 0.8;
  flex-wrap: wrap;
  gap: 10px;
}
.dashboard-reset {
  background: transparent;
  color: rgba(255, 255, 255, 0.85);
  border: 1px solid rgba(255, 255, 255, 0.35);
  padding: 5px 12px;
  border-radius: 6px;
  font-size: 11.5px;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.15s;
}
.dashboard-reset:hover { background: rgba(255, 255, 255, 0.15); color: white; }

/* 토픽 카드 연습시험 뱃지 */
.topic-card .exam-badge {
  display: inline-block;
  margin-top: 6px;
  font-size: 11.5px;
  padding: 2px 10px;
  border-radius: 999px;
  background: var(--success-soft);
  color: var(--success);
  font-weight: 600;
  letter-spacing: 0.2px;
}

/* Breadth Exam 특별 카드 */
.mock-exam-card {
  background: linear-gradient(135deg, #831843, #be185d);
  color: white;
  border-radius: 14px;
  padding: 26px 28px;
  display: block;
  transition: all 0.2s;
  box-shadow: 0 6px 18px rgba(190, 24, 93, 0.2);
}
.mock-exam-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 14px 32px rgba(190, 24, 93, 0.3);
  text-decoration: none;
  color: white;
}
.mock-exam-card h3 { margin: 0 0 8px; font-size: 22px; color: white; }
.mock-exam-card p { margin: 0 0 4px; opacity: 0.92; font-size: 14.5px; }
.mock-exam-card .meta { font-size: 13px; opacity: 0.8; margin-top: 8px; }

/* ========== 반응형 ========== */
@media (max-width: 640px) {
  .hero { padding: 40px 20px 44px; }
  .hero h1 { font-size: 22px; }
  main { padding: 16px 14px 40px; }
  .problem-head, .problem-body, .solution { padding-left: 18px; padding-right: 18px; }
  .nav-inner { flex-wrap: wrap; }
  .katex-display { font-size: 1em; }
  .dashboard-card { padding: 20px 18px; }
  .stat-card .stat-num { font-size: 24px; }
}