/* วิทยาศาสตร์ ม.ต้น - สีถนอมสายตา + โหมดกลางวัน/กลางคืน + มือถือ */
:root {
  /* โหมดกลางวัน - สีอ่อน ถนอมสายตา */
  --bg: #f5f7f4;
  --bg-card: #ffffff;
  --bg-soft: #eef2ea;
  --text: #2c3e2d;
  --text-muted: #5a6b5c;
  --primary: #3d7a5a;
  --primary-light: #5a9a75;
  --accent: #4a90a4;
  --border: #d4ddd0;
  --shadow: 0 2px 12px rgba(44, 62, 45, 0.08);
  --success: #2e7d4f;
  --danger: #c44536;
  --warning: #d4a017;
  --radius: 12px;
  --header-h: 56px;
}

[data-theme="dark"] {
  --bg: #1a1f1c;
  --bg-card: #242b26;
  --bg-soft: #2a322c;
  --text: #e4ebe5;
  --text-muted: #a0aea3;
  --primary: #6bbf8a;
  --primary-light: #8fd4a8;
  --accent: #7eb8c9;
  --border: #3a453d;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.35);
  --success: #5cbf7a;
  --danger: #e07060;
  --warning: #e6b84d;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'Sarabun', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  font-size: 16px;
  min-height: 100vh;
  transition: background 0.3s, color 0.3s;
}

/* Header */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  height: var(--header-h);
  box-shadow: var(--shadow);
}

.header-inner {
  max-width: 960px;
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 12px;
}

.menu-toggle {
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--text);
  cursor: pointer;
  padding: 8px;
  line-height: 1;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  color: var(--primary);
  font-weight: 600;
  font-size: 1.15rem;
}

.logo-icon { font-size: 1.4rem; }

.header-actions {
  display: flex;
  gap: 4px;
}

.theme-btn, .user-btn {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s;
}

.theme-btn:hover, .user-btn:hover {
  background: var(--primary);
  color: #fff;
}

/* Sidebar */
.sidebar {
  position: fixed;
  top: 0;
  left: -280px;
  width: 280px;
  height: 100%;
  background: var(--bg-card);
  z-index: 200;
  transition: left 0.3s ease;
  overflow-y: auto;
  border-right: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.sidebar.open { left: 0; }

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

.sidebar-header h2 { font-size: 1.1rem; color: var(--primary); }

.close-menu {
  background: none;
  border: none;
  font-size: 1.3rem;
  color: var(--text-muted);
  cursor: pointer;
}

.nav-list { list-style: none; padding: 8px 0; }

.nav-link, .nav-group-btn {
  display: block;
  width: 100%;
  padding: 12px 16px;
  text-decoration: none;
  color: var(--text);
  background: none;
  border: none;
  text-align: left;
  font-size: 1rem;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.2s;
}

.nav-link:hover, .nav-group-btn:hover,
.nav-link.active { background: var(--bg-soft); color: var(--primary); }

.nav-sub {
  list-style: none;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s;
  background: var(--bg-soft);
}

.nav-group.open .nav-sub { max-height: 400px; }

.nav-sub a {
  display: block;
  padding: 10px 16px 10px 28px;
  text-decoration: none;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.nav-sub a:hover { color: var(--primary); }

.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 150;
}

.overlay.show { display: block; }

/* Main */
.main {
  max-width: 960px;
  margin: 0 auto;
  padding: 20px 14px 60px;
}

.hero {
  text-align: center;
  padding: 28px 12px;
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  margin-bottom: 28px;
}

.hero h1 {
  font-size: 1.6rem;
  color: var(--primary);
  margin-bottom: 8px;
}

.hero-sub {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-bottom: 20px;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
}

.stat-card {
  background: var(--bg-soft);
  padding: 12px 20px;
  border-radius: 10px;
  min-width: 120px;
}

.stat-num {
  display: block;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
}

.stat-label { font-size: 0.85rem; color: var(--text-muted); }

/* Grade cards */
.grade-section, .lesson-section, .quick-links {
  margin-bottom: 32px;
}

.grade-section h2, .lesson-section h2, .quick-links h2 {
  font-size: 1.25rem;
  margin-bottom: 14px;
  color: var(--text);
  padding-left: 4px;
  border-left: 4px solid var(--primary);
  padding-left: 12px;
}

.grade-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
}

.grade-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 12px;
  text-align: center;
  text-decoration: none;
  color: var(--text);
  box-shadow: var(--shadow);
  transition: transform 0.2s, border-color 0.2s;
}

.grade-card:hover, .grade-card:active {
  transform: translateY(-2px);
  border-color: var(--primary);
}

.grade-num {
  display: block;
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary);
}

.grade-desc {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 4px;
  display: block;
}

/* Lesson cards */
.lesson-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}

@media (min-width: 520px) {
  .lesson-grid { grid-template-columns: 1fr 1fr; }
}

.lesson-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  text-decoration: none;
  color: var(--text);
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: border-color 0.2s;
}

.lesson-card:hover { border-color: var(--primary); }

.lesson-icon { font-size: 1.8rem; }

.lesson-card h3 {
  font-size: 1.05rem;
  color: var(--primary);
}

.lesson-card p {
  font-size: 0.9rem;
  color: var(--text-muted);
  flex: 1;
}

.lesson-badge {
  font-size: 0.75rem;
  padding: 3px 8px;
  border-radius: 20px;
  background: var(--bg-soft);
  color: var(--text-muted);
  align-self: flex-start;
}

.lesson-badge.done {
  background: rgba(46, 125, 79, 0.15);
  color: var(--success);
}

.lesson-badge.partial {
  background: rgba(212, 160, 23, 0.15);
  color: var(--warning);
}

/* Quick links */
.quick-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.quick-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  text-align: center;
  text-decoration: none;
  color: var(--text);
  font-weight: 500;
  box-shadow: var(--shadow);
  transition: background 0.2s;
}

.quick-card:hover { background: var(--bg-soft); color: var(--primary); }

/* Footer */
.footer {
  text-align: center;
  padding: 24px 14px;
  font-size: 0.85rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  margin-top: 20px;
}

.footer-note { margin-top: 8px; font-size: 0.8rem; }

/* Modal */
.modal {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 300;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.modal.show { display: flex; }

.modal-content {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 24px;
  max-width: 360px;
  width: 100%;
  box-shadow: var(--shadow);
}

.modal-content h3 { margin-bottom: 8px; color: var(--primary); }

.modal-content p { font-size: 0.9rem; color: var(--text-muted); margin-bottom: 16px; }

.modal-content label {
  display: block;
  font-size: 0.9rem;
  margin-bottom: 6px;
}

.modal-content input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  font-family: inherit;
  background: var(--bg);
  color: var(--text);
  margin-bottom: 16px;
}

.modal-actions {
  display: flex;
  gap: 10px;
}

/* Buttons */
.btn {
  padding: 10px 18px;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-family: inherit;
  cursor: pointer;
  font-weight: 500;
  transition: opacity 0.2s;
}

.btn:hover { opacity: 0.9; }

.btn-primary {
  background: var(--primary);
  color: #fff;
  flex: 1;
}

.btn-secondary {
  background: var(--bg-soft);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-success { background: var(--success); color: #fff; }
.btn-danger { background: var(--danger); color: #fff; }

/* ========== Lesson Page Styles ========== */
.lesson-page {
  max-width: 800px;
  margin: 0 auto;
  padding: 16px 14px 80px;
}

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

.lesson-header .back {
  display: inline-block;
  color: var(--primary);
  text-decoration: none;
  font-size: 0.9rem;
  margin-bottom: 8px;
}

.lesson-header h1 {
  font-size: 1.45rem;
  color: var(--primary);
  margin-bottom: 6px;
}

.lesson-meta {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.content-block {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 18px;
  margin-bottom: 16px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.content-block h2 {
  font-size: 1.15rem;
  color: var(--primary);
  margin-bottom: 12px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

.content-block h3 {
  font-size: 1.05rem;
  margin: 16px 0 8px;
  color: var(--text);
}

.content-block p, .content-block li {
  margin-bottom: 10px;
  color: var(--text);
}

.content-block ul, .content-block ol {
  padding-left: 22px;
  margin-bottom: 12px;
}

.content-block img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
  margin: 12px 0;
  display: block;
}

.example-box {
  background: var(--bg-soft);
  border-left: 4px solid var(--accent);
  padding: 12px 14px;
  margin: 12px 0;
  border-radius: 0 8px 8px 0;
}

.example-box .ex-title {
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 6px;
  font-size: 0.95rem;
}

.note-box {
  background: rgba(61, 122, 90, 0.1);
  border: 1px solid var(--primary);
  padding: 12px;
  border-radius: 8px;
  margin: 12px 0;
  font-size: 0.95rem;
}

/* Quiz */
.quiz-section {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 18px;
  border: 1px solid var(--border);
  margin-top: 24px;
}

.quiz-section h2 {
  color: var(--primary);
  margin-bottom: 16px;
}

.quiz-item {
  margin-bottom: 20px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border);
}

.quiz-item:last-of-type { border-bottom: none; }

.quiz-q {
  font-weight: 500;
  margin-bottom: 10px;
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.quiz-options label {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  padding: 10px 12px;
  background: var(--bg-soft);
  border-radius: 8px;
  cursor: pointer;
  border: 2px solid transparent;
  transition: border-color 0.2s;
}

.quiz-options label:hover { border-color: var(--primary-light); }

.quiz-options input { margin-top: 3px; accent-color: var(--primary); }

.quiz-options label.correct {
  border-color: var(--success);
  background: rgba(46, 125, 79, 0.12);
}

.quiz-options label.wrong {
  border-color: var(--danger);
  background: rgba(196, 69, 54, 0.1);
}

.quiz-explain {
  display: none;
  margin-top: 10px;
  padding: 10px;
  background: var(--bg-soft);
  border-radius: 8px;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.quiz-explain.show { display: block; }

.quiz-actions {
  margin-top: 20px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.quiz-result {
  margin-top: 16px;
  padding: 14px;
  border-radius: 8px;
  font-weight: 500;
  display: none;
}

.quiz-result.show { display: block; }

.quiz-result.pass {
  background: rgba(46, 125, 79, 0.15);
  color: var(--success);
}

.quiz-result.fail {
  background: rgba(196, 69, 54, 0.12);
  color: var(--danger);
}

/* Progress / Evaluate / Certificate */
.progress-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.progress-table th, .progress-table td {
  padding: 10px 8px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.progress-table th {
  background: var(--bg-soft);
  color: var(--primary);
  font-weight: 600;
}

/* Certificate preview */
.cert-preview {
  background: #fff;
  color: #222;
  padding: 32px 24px;
  border: 3px solid #3d7a5a;
  border-radius: 8px;
  text-align: center;
  max-width: 600px;
  margin: 20px auto;
}

.cert-preview h2 {
  color: #3d7a5a;
  font-size: 1.5rem;
  margin-bottom: 8px;
}

.cert-preview .cert-name {
  font-size: 1.4rem;
  font-weight: 700;
  margin: 16px 0;
  color: #1a3a2a;
}

/* Game */
.game-area {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 20px;
  border: 1px solid var(--border);
  text-align: center;
}

.game-score {
  font-size: 1.2rem;
  margin-bottom: 16px;
  color: var(--primary);
}

.game-card {
  display: inline-block;
  padding: 16px 24px;
  margin: 6px;
  background: var(--bg-soft);
  border: 2px solid var(--border);
  border-radius: 10px;
  cursor: pointer;
  font-size: 1rem;
  transition: all 0.2s;
  min-width: 100px;
}

.game-card:hover { border-color: var(--primary); }
.game-card.selected { border-color: var(--primary); background: rgba(61,122,90,0.15); }
.game-card.matched { opacity: 0.4; pointer-events: none; }

/* Utility */
.text-center { text-align: center; }
.mt-2 { margin-top: 16px; }
.mb-2 { margin-bottom: 16px; }

@media (min-width: 768px) {
  .menu-toggle { display: none; }
  .sidebar {
    left: 0;
    width: 240px;
    box-shadow: none;
  }
  .main, .lesson-page {
    margin-left: 240px;
    max-width: calc(100% - 240px);
  }
  .header-inner { padding-left: 16px; }
  .overlay { display: none !important; }
  .close-menu { display: none; }
}