:root {
  --primary: #6b3fa0;
  --primary-light: #9d6fd1;
  --primary-bg: #f3eaff;
  --accent: #ff8c42;
  --success: #2bb673;
  --danger: #e74c3c;
  --warning: #f4a623;
  --text: #1f2330;
  --text-light: #5b6071;
  --bg: #f6f7fb;
  --card: #ffffff;
  --border: #e6e6ef;
  --shadow: 0 2px 12px rgba(60, 30, 100, 0.06);
  --radius: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Sarabun", "Noto Sans Thai", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
button { font-family: inherit; cursor: pointer; }

/* Top bar */
.topbar {
  background: linear-gradient(135deg, #6b3fa0 0%, #9d6fd1 100%);
  color: white;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  position: sticky;
  top: 0;
  z-index: 10;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}
.brand { display: flex; align-items: center; gap: 12px; }
.brand-logo {
  width: 44px; height: 44px;
  background: white;
  color: var(--primary);
  border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  font-weight: 800;
  font-size: 16px;
}
.brand-title { font-weight: 700; font-size: 18px; }
.brand-sub { font-size: 12px; opacity: 0.85; }
.topnav { display: flex; gap: 6px; align-items: center; }
.nav-link {
  color: rgba(255,255,255,0.9);
  padding: 8px 14px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 500;
}
.nav-link:hover { background: rgba(255,255,255,0.15); text-decoration: none; }
.nav-link.active { background: rgba(255,255,255,0.22); color: white; }
.reset-btn {
  background: rgba(255,255,255,0.18);
  color: white;
  border: 1px solid rgba(255,255,255,0.3);
  padding: 7px 14px;
  border-radius: 8px;
  font-size: 13px;
}
.reset-btn:hover { background: rgba(255,255,255,0.3); }

/* Main */
.app {
  max-width: 1100px;
  margin: 0 auto;
  padding: 28px 24px 60px;
}

.footer {
  text-align: center;
  color: var(--text-light);
  font-size: 13px;
  padding: 20px;
  border-top: 1px solid var(--border);
}

/* Page header */
.page-title {
  font-size: 28px;
  font-weight: 700;
  margin: 0 0 6px;
}
.page-sub {
  color: var(--text-light);
  margin: 0 0 24px;
}

/* Welcome card */
.welcome-card {
  background: linear-gradient(135deg, #ffffff 0%, #faf6ff 100%);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 24px;
  margin-bottom: 22px;
  display: flex; gap: 18px; align-items: center;
  box-shadow: var(--shadow);
}
.welcome-emoji { font-size: 42px; }
.welcome-text h2 { margin: 0 0 4px; font-size: 20px; }
.welcome-text p { margin: 0; color: var(--text-light); font-size: 14px; }
.name-input {
  border: 1px solid var(--border);
  padding: 6px 10px;
  border-radius: 8px;
  font-size: 14px;
  font-family: inherit;
}

/* Stats row */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 14px;
  margin-bottom: 22px;
}
.stat-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  box-shadow: var(--shadow);
}
.stat-label { font-size: 12px; color: var(--text-light); text-transform: uppercase; letter-spacing: 0.6px; }
.stat-value { font-size: 26px; font-weight: 700; margin-top: 4px; color: var(--primary); }
.stat-hint { font-size: 12px; color: var(--text-light); margin-top: 4px; }

/* Section title */
.section-title {
  font-size: 16px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--text-light);
  margin: 30px 0 12px;
}

/* Subject grid */
.subject-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 14px;
}
.subject-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
  display: flex;
  flex-direction: column;
  gap: 10px;
  box-shadow: var(--shadow);
}
.subject-card:hover {
  transform: translateY(-2px);
  border-color: var(--primary-light);
  box-shadow: 0 6px 18px rgba(107, 63, 160, 0.12);
}
.subject-card-head {
  display: flex; align-items: center; gap: 12px;
}
.subject-icon {
  font-size: 28px;
  width: 50px; height: 50px;
  display: flex; align-items: center; justify-content: center;
  border-radius: 12px;
  background: var(--primary-bg);
}
.subject-name { font-weight: 700; font-size: 17px; }
.subject-date { font-size: 12px; color: var(--text-light); }

.progress-bar {
  width: 100%;
  height: 8px;
  background: #ececf3;
  border-radius: 999px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary) 0%, var(--primary-light) 100%);
  border-radius: 999px;
  transition: width 0.4s;
}
.subject-stats {
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--text-light);
}
.subject-stats b { color: var(--text); font-size: 13px; }

/* Subject page */
.back-link {
  font-size: 14px;
  color: var(--primary);
  margin-bottom: 16px;
  display: inline-block;
}
.subject-header {
  display: flex; align-items: center; gap: 16px;
  margin-bottom: 8px;
}
.subject-header .subject-icon { width: 60px; height: 60px; font-size: 32px; }
.subject-header h1 { margin: 0; font-size: 26px; }

.group-tabs {
  display: flex; gap: 8px; flex-wrap: wrap;
  margin: 18px 0 6px;
}
.group-tab {
  background: var(--card);
  border: 1px solid var(--border);
  padding: 8px 14px;
  border-radius: 999px;
  font-size: 13px;
  color: var(--text-light);
}
.group-tab.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.section-tabs {
  display: flex; gap: 0;
  border-bottom: 2px solid var(--border);
  margin: 18px 0 20px;
}
.section-tab {
  background: transparent;
  border: none;
  padding: 10px 18px;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-light);
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
}
.section-tab.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

/* Lessons */
.lesson-list { display: flex; flex-direction: column; gap: 10px; }
.lesson-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
}
.lesson-head {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 18px;
  cursor: pointer;
  gap: 12px;
}
.lesson-head:hover { background: #fafafd; }
.lesson-title { font-weight: 600; }
.lesson-title small { color: var(--text-light); font-weight: 400; margin-left: 8px; font-size: 12px; }
.lesson-actions { display: flex; align-items: center; gap: 12px; }
.lesson-check {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 13px;
  color: var(--text-light);
  cursor: pointer;
  padding: 4px 10px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: white;
}
.lesson-check.done {
  background: #e7f7ef;
  border-color: var(--success);
  color: var(--success);
  font-weight: 600;
}
.lesson-toggle {
  width: 26px; height: 26px;
  border-radius: 50%;
  background: var(--primary-bg);
  color: var(--primary);
  display: inline-flex; align-items: center; justify-content: center;
  transition: transform 0.2s;
}
.lesson-item.open .lesson-toggle { transform: rotate(180deg); }
.lesson-body {
  display: none;
  padding: 0 22px 20px;
  border-top: 1px solid var(--border);
}
.lesson-item.open .lesson-body { display: block; }
.lesson-body h4 { margin: 16px 0 8px; color: var(--primary); }
.lesson-body p, .lesson-body li { font-size: 15px; }
.lesson-body code, .lesson-body .ex {
  background: #f4f1fa;
  padding: 2px 6px;
  border-radius: 4px;
  font-family: "SF Mono", Menlo, monospace;
  font-size: 14px;
  color: var(--primary);
}
.lesson-body .example-box {
  background: #fff8ee;
  border-left: 4px solid var(--warning);
  padding: 10px 14px;
  border-radius: 6px;
  margin: 10px 0;
}
.lesson-body .tip-box {
  background: #eaf7ef;
  border-left: 4px solid var(--success);
  padding: 10px 14px;
  border-radius: 6px;
  margin: 10px 0;
}
.lesson-body .formula {
  background: #f0ebf9;
  padding: 10px 14px;
  border-radius: 6px;
  margin: 10px 0;
  font-family: "SF Mono", Menlo, monospace;
  font-size: 15px;
  text-align: center;
}
.lesson-body .speak-btn {
  background: var(--primary-bg);
  border: 1px solid transparent;
  color: var(--primary);
  cursor: pointer;
  padding: 2px 7px;
  border-radius: 999px;
  font-size: 13px;
  line-height: 1;
  display: inline-flex;
  align-items: center;
  gap: 2px;
  margin-left: 4px;
  vertical-align: middle;
  transition: background 0.12s, transform 0.08s;
}
.lesson-body .speak-btn:hover {
  background: var(--primary);
  color: white;
  transform: scale(1.05);
}
.lesson-body .speak-btn:active {
  transform: scale(0.95);
}
.lesson-body .zh {
  font-family: "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  font-weight: 600;
  color: #1f2330;
}

.lesson-body .illustration {
  display: block;
  margin: 16px auto;
  max-width: 100%;
  height: auto;
  background: #fdfcff;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  box-shadow: 0 1px 4px rgba(60, 30, 100, 0.05);
}
.lesson-body .illustration-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
  margin: 16px 0;
}
.lesson-body .illustration-row .illustration {
  margin: 0;
  flex: 0 0 auto;
}
.lesson-body .illustration-caption {
  text-align: center;
  font-size: 13px;
  color: var(--text-light);
  margin-top: -4px;
  margin-bottom: 14px;
}
.lesson-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 10px 0;
  font-size: 14px;
}
.lesson-body th, .lesson-body td {
  border: 1px solid var(--border);
  padding: 8px 10px;
  text-align: left;
}
.lesson-body th { background: var(--primary-bg); color: var(--primary); }

/* Quizzes */
.quiz-list { display: flex; flex-direction: column; gap: 12px; }
.quiz-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  display: flex; justify-content: space-between; align-items: center;
  gap: 16px;
  box-shadow: var(--shadow);
}
.quiz-meta { flex: 1; }
.quiz-meta h3 { margin: 0 0 4px; font-size: 16px; }
.quiz-meta p { margin: 0; font-size: 13px; color: var(--text-light); }
.btn {
  background: var(--primary);
  color: white;
  border: none;
  padding: 9px 18px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  transition: background 0.15s;
}
.btn:hover { background: #5a3387; }
.btn.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--primary);
}
.btn.btn-outline:hover { background: var(--primary-bg); }
.btn.btn-success { background: var(--success); }
.btn.btn-success:hover { background: #239e63; }
.btn.btn-secondary { background: #eee; color: var(--text); }
.btn.btn-secondary:hover { background: #e1e1e8; }

.score-badge {
  display: inline-block;
  font-size: 12px;
  padding: 3px 10px;
  border-radius: 999px;
  background: var(--primary-bg);
  color: var(--primary);
  font-weight: 600;
}
.score-badge.good { background: #e7f7ef; color: var(--success); }
.score-badge.ok { background: #fff4e0; color: var(--warning); }
.score-badge.low { background: #fbeae6; color: var(--danger); }

/* Quiz page */
.quiz-page { max-width: 720px; margin: 0 auto; }
.quiz-question {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 14px;
  box-shadow: var(--shadow);
}
.quiz-q-num {
  display: inline-block;
  background: var(--primary-bg);
  color: var(--primary);
  font-weight: 700;
  font-size: 12px;
  padding: 3px 10px;
  border-radius: 999px;
  margin-bottom: 8px;
}
.quiz-q-text { font-size: 16px; font-weight: 600; margin-bottom: 14px; }
.quiz-options { display: flex; flex-direction: column; gap: 8px; }
.quiz-option {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  background: white;
  transition: border-color 0.1s, background 0.1s;
}
.quiz-option:hover { border-color: var(--primary-light); }
.quiz-option input { margin-top: 4px; }
.quiz-option.selected { border-color: var(--primary); background: var(--primary-bg); }
.quiz-option.correct { border-color: var(--success); background: #e7f7ef; }
.quiz-option.wrong { border-color: var(--danger); background: #fbeae6; }

.quiz-explanation {
  margin-top: 12px;
  padding: 12px 14px;
  background: #fff8ee;
  border-left: 4px solid var(--warning);
  border-radius: 6px;
  font-size: 14px;
}
.quiz-explanation b { color: var(--warning); }

.quiz-actions {
  display: flex; gap: 10px; justify-content: flex-end;
  margin-top: 18px;
}

/* Results */
.result-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-align: center;
  margin-bottom: 20px;
  box-shadow: var(--shadow);
}
.result-score {
  font-size: 48px;
  font-weight: 700;
  margin: 8px 0;
  color: var(--primary);
}
.result-message { color: var(--text-light); margin-bottom: 16px; }

/* History */
.history-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--card);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
}
.history-table th, .history-table td {
  padding: 12px 14px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  font-size: 14px;
}
.history-table th {
  background: var(--primary-bg);
  color: var(--primary);
  font-weight: 600;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
}
.history-table tr:last-child td { border-bottom: none; }
.empty-state {
  text-align: center;
  padding: 40px 20px;
  color: var(--text-light);
}
.empty-state .emoji { font-size: 48px; }

/* Timetable */
.timetable-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow);
  margin-bottom: 14px;
  display: grid;
  grid-template-columns: 60px 1fr auto;
  gap: 16px;
  align-items: center;
}
.timetable-date {
  background: var(--primary-bg);
  color: var(--primary);
  border-radius: 10px;
  padding: 8px;
  text-align: center;
}
.timetable-date .day { font-size: 20px; font-weight: 700; line-height: 1; }
.timetable-date .month { font-size: 11px; text-transform: uppercase; }

@media (max-width: 600px) {
  .topbar { padding: 12px; }
  .brand-title { font-size: 16px; }
  .brand-sub { font-size: 11px; }
  .nav-link { padding: 6px 10px; font-size: 13px; }
  .app { padding: 20px 14px; }
  .page-title { font-size: 22px; }
  .welcome-card { flex-direction: column; text-align: center; }
  .quiz-card { flex-direction: column; align-items: stretch; }
}