:root {
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #e0e7ff;
  --bg: #f8fafc;
  --surface: #ffffff;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-muted: #64748b;
  --success: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-lg: 0 10px 30px rgba(0,0,0,0.1);
  --transition: 0.2s ease;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
a { text-decoration: none; color: inherit; }

.page-loader { position: fixed; inset: 0; z-index: 999; background: var(--bg); display: flex; align-items: center; justify-content: center; transition: opacity 0.3s; }
.page-loader.hidden { opacity: 0; pointer-events: none; }
.loader-spin { width: 36px; height: 36px; border: 3px solid var(--border); border-top-color: var(--primary); border-radius: 50%; animation: spin 0.7s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

/* Dark theme */
.page-dark {
  background: linear-gradient(135deg, #0f172a 0%, #1e293b 50%, #0f172a 100%);
  min-height: 100vh;
  color: #e2e8f0;
}
.page-dark .navbar { background: rgba(15,23,42,0.8); border-bottom: 1px solid rgba(255,255,255,0.08); backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px); }
.page-dark .logo { color: #818cf8; }
.page-dark .logo-sub { color: #94a3b8; }
.page-dark .btn { color: #cbd5e1; border-color: rgba(255,255,255,0.15); background: rgba(255,255,255,0.04); }
.page-dark .btn:hover { background: rgba(255,255,255,0.08); border-color: rgba(255,255,255,0.25); }
.page-dark .btn-primary { background: var(--primary); color: #fff; border-color: var(--primary); }
.page-dark .btn-primary:hover { background: var(--primary-hover); }
.page-dark .hamburger span { background: #e2e8f0; }
.page-dark .form-input, .page-dark .form-select, .page-dark textarea {
  border-color: rgba(255,255,255,0.12);
  background: rgba(255,255,255,0.06);
  color: #e2e8f0;
}
.page-dark .card {
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.08);
}
.page-dark .empty { color: #64748b; }
@media (max-width: 900px) {
  .page-dark .nav-right { background: #1e293b; border-color: rgba(255,255,255,0.08); }
}

/* Navbar */
.navbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 24px; height: 56px;
  background: var(--surface); border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 100;
}
.nav-left { display: flex; align-items: center; gap: 12px; }
.logo { font-size: 22px; font-weight: 700; color: var(--primary); }
.logo-sub { font-size: 13px; color: var(--text-muted); }
.nav-right { display: flex; align-items: center; gap: 8px; }
.nav-user { font-size: 13px; color: var(--text-muted); padding-right: 12px; border-right: 1px solid var(--border); }
.hamburger { display: none; flex-direction: column; gap: 5px; background: none; border: none; cursor: pointer; padding: 6px; }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 8px 16px; border: 1px solid var(--border); border-radius: 8px;
  background: var(--surface); color: var(--text); font-size: 14px;
  cursor: pointer; transition: var(--transition); white-space: nowrap;
  font-family: inherit; line-height: 1.4;
}
.btn:hover { background: var(--bg); }
.btn-primary { background: var(--primary); color: #fff; border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-hover); }
.btn-outline { background: transparent; }
.btn-sm { padding: 6px 12px; font-size: 13px; }
.btn-lg { padding: 12px 24px; font-size: 16px; }
.btn-full { width: 100%; justify-content: center; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.btn-danger { color: var(--danger); border-color: var(--danger); }
.btn-danger:hover { background: rgba(239,68,68,0.08); }

/* Forms */
.form-group { margin-bottom: 16px; }
.form-group label { display: block; font-size: 13px; font-weight: 500; margin-bottom: 4px; }
.form-input, .form-select, textarea {
  width: 100%; padding: 10px 12px; border: 1px solid var(--border);
  border-radius: 8px; font-size: 14px; font-family: inherit;
  transition: var(--transition);
}
.form-input:focus, .form-select:focus, textarea:focus {
  outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px rgba(79,70,229,0.1);
}
.form-error { color: var(--danger); font-size: 13px; min-height: 20px; margin-bottom: 8px; }
.form-row { display: flex; gap: 12px; }
.form-row > * { flex: 1; }
.form-hint { display: block; font-size: 11px; color: var(--text-muted); margin-top: 4px; }

/* Cards */
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px;
  transition: var(--transition);
}
.card:hover { box-shadow: var(--shadow-lg); }

/* Toast */
.toast-container { position: fixed; top: 72px; right: 20px; z-index: 300; display: flex; flex-direction: column; gap: 8px; }
.toast { padding: 12px 20px; border-radius: 10px; font-size: 14px; box-shadow: var(--shadow-lg); max-width: 360px; color: #fff; animation: slideIn 0.3s ease; }
.toast-success { background: var(--success); }
.toast-error { background: var(--danger); }
.toast-info { background: var(--primary); }
@keyframes slideIn { from { transform: translateX(100%); opacity: 0; } to { transform: translateX(0); opacity: 1; } }

/* Container */
.container { max-width: 1200px; margin: 0 auto; padding: 24px; }
.empty { text-align: center; padding: 60px 20px; color: var(--text-muted); font-size: 14px; }
.empty svg { margin-bottom: 16px; opacity: 0.3; }

/* Auth page */
.auth-page {
  display: flex; align-items: center; justify-content: center;
  min-height: 100vh;
  background: linear-gradient(135deg, #0f0c29 0%, #302b63 40%, #24243e 100%);
  position: relative; overflow: hidden;
}
.auth-container { width: 380px; max-width: 90vw; position: relative; z-index: 1; }
.auth-card {
  background: rgba(255,255,255,0.97); border-radius: 20px;
  padding: 48px 36px; text-align: center;
  box-shadow: 0 32px 64px rgba(15,12,41,0.25);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}
.auth-logo { font-size: 28px; font-weight: 700; color: var(--primary); margin-bottom: 4px; }
.auth-sub { color: var(--text-muted); font-size: 14px; margin-bottom: 28px; }
.auth-form { text-align: left; }

/* Textbooks grid */
.textbooks-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}
.textbook-card { cursor: pointer; }
.textbook-card:hover { transform: translateY(-2px); }
.textbook-card .subject-badge {
  display: inline-block; padding: 2px 10px; border-radius: 10px;
  font-size: 11px; font-weight: 600; margin-bottom: 8px;
}
.subject-chinese { background: rgba(239,68,68,0.12); color: #f87171; }
.subject-math { background: rgba(59,130,246,0.12); color: #60a5fa; }
.subject-english { background: rgba(16,185,129,0.12); color: #34d399; }
.subject-science { background: rgba(245,158,11,0.12); color: #fbbf24; }
.subject-morality { background: rgba(168,85,247,0.12); color: #c4b5fd; }
.subject-history { background: rgba(139,92,246,0.12); color: #a78bfa; }
.subject-geography { background: rgba(20,184,166,0.12); color: #2dd4bf; }
.subject-biology { background: rgba(34,197,94,0.12); color: #4ade80; }
.subject-physics { background: rgba(14,165,233,0.12); color: #38bdf8; }
.subject-chemistry { background: rgba(236,72,153,0.12); color: #f472b6; }
.textbook-card h3 { font-size: 16px; margin-bottom: 4px; }
.textbook-card .meta { font-size: 12px; color: var(--text-muted); margin-top: 8px; }

/* Import page */
.import-dropzone {
  border: 2px dashed var(--border); border-radius: var(--radius);
  padding: 48px; text-align: center; cursor: pointer;
  transition: all 0.2s; margin-bottom: 24px;
}
.import-dropzone:hover, .import-dropzone.drag-over {
  border-color: var(--primary); background: var(--primary-light);
}
.import-dropzone p { color: var(--text-muted); margin-top: 12px; }
.import-preview { max-height: 60vh; overflow-y: auto; background: rgba(0,0,0,0.2); border-radius: var(--radius); padding: 20px; font-family: 'SF Mono', Consolas, monospace; font-size: 13px; line-height: 1.8; white-space: pre-wrap; }

/* Exercise page */
.exercise-layout { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.exercise-preview {
  background: #fff; color: #1e293b; padding: 40px; border-radius: 8px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.15); min-height: 500px;
  font-size: 15px; line-height: 2.2;
}
.exercise-preview .exam-title { text-align: center; font-size: 20px; font-weight: 700; margin-bottom: 4px; }
.exercise-preview .exam-subtitle { text-align: center; font-size: 13px; color: #64748b; margin-bottom: 8px; }
.exercise-preview .exam-info { display: flex; justify-content: space-between; font-size: 13px; margin-bottom: 24px; padding-bottom: 12px; border-bottom: 1px solid #e2e8f0; }
.exercise-preview .question-item { margin-bottom: 16px; }
.exercise-preview .question-no { font-weight: 600; margin-right: 8px; }
.exercise-preview .blank { display: inline-block; min-width: 80px; border-bottom: 1px solid #333; text-align: center; margin: 0 4px; }
.exercise-preview .answer-section { margin-top: 40px; padding-top: 20px; border-top: 2px dashed #e2e8f0; }
.exercise-preview .answer-section h4 { color: var(--danger); margin-bottom: 12px; }
.exercise-preview .answer-item { font-size: 13px; color: #64748b; margin-bottom: 4px; }

/* Loading */
.loading { text-align: center; padding: 40px; color: var(--text-muted); }

/* Responsive */
@media (max-width: 900px) {
  .exercise-layout { grid-template-columns: 1fr; }
  .textbooks-grid { grid-template-columns: repeat(2, 1fr); }
  .hamburger { display: flex; }
  .nav-right { display: none; position: absolute; top: 56px; left: 0; right: 0; background: var(--surface); flex-direction: column; padding: 12px; border-bottom: 1px solid var(--border); box-shadow: var(--shadow-lg); z-index: 105; }
  .nav-right.open { display: flex; }
  .nav-user { border-right: none; }
}
@media (max-width: 560px) {
  .container { padding: 12px; }
  .textbooks-grid { grid-template-columns: 1fr; }
  .form-row { flex-direction: column; }
  .exercise-preview { padding: 24px; }
}

/* ==================== Schedule Table ==================== */
.schedule-table-wrap {
  overflow-x: auto;
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 16px;
}
.schedule-table {
  width: 100%;
  border-collapse: collapse;
  table-layout: fixed;
}
.schedule-table th {
  padding: 14px 8px;
  text-align: center;
  font-size: 14px;
  font-weight: 600;
  color: #94a3b8;
  border-bottom: 1px solid rgba(255,255,255,0.08);
}
.schedule-table th:first-child { width: 100px; }
.schedule-table td {
  padding: 0;
  border: 1px solid rgba(255,255,255,0.04);
  vertical-align: top;
}
.schedule-cell {
  min-height: 68px;
  padding: 8px;
  cursor: pointer;
  transition: all 0.15s;
  text-align: center;
}
.schedule-cell:hover {
  filter: brightness(1.2);
  transform: scale(1.02);
  z-index: 1;
  position: relative;
}
.cell-subject { font-size: 14px; font-weight: 600; }
.cell-detail { font-size: 11px; opacity: 0.8; margin-top: 2px; }
.schedule-cell.has-course { transition: all 0.15s; }
.schedule-cell.has-course:hover { filter: brightness(1.15); transform: scale(1.03); z-index: 2; position: relative; }
.schedule-cell.editing { padding: 4px !important; min-width: 110px; z-index: 5; position: relative; }
.cell-edit-form { display: flex; flex-direction: column; gap: 4px; min-width: 100px; }
.cell-edit-select { width: 100%; padding: 4px; border: 1px solid rgba(255,255,255,0.3); border-radius: 4px; font-size: 12px; font-family: inherit; background: rgba(0,0,0,0.3); color: #fff; }
.cell-edit-select:focus { outline: none; border-color: #fff; }
.cell-edit-input { width: 100%; padding: 3px 5px; border: 1px solid rgba(255,255,255,0.2); border-radius: 4px; font-size: 11px; font-family: inherit; background: rgba(0,0,0,0.2); color: #fff; }
.cell-edit-input::placeholder { color: rgba(255,255,255,0.4); }
.cell-edit-input:focus { outline: none; border-color: #fff; }
.cell-edit-btns { display: flex; gap: 4px; justify-content: center; }
.cell-edit-save, .cell-edit-cancel { width: 24px; height: 24px; border: none; border-radius: 50%; cursor: pointer; font-size: 12px; display: flex; align-items: center; justify-content: center; }
.cell-edit-save { background: var(--success); color: #fff; }
.cell-edit-cancel { background: rgba(255,255,255,0.15); color: #fff; }

.period-cell {
  padding: 8px 6px !important;
  text-align: center;
  background: rgba(255,255,255,0.02);
}
.period-name { font-size: 13px; font-weight: 500; color: #cbd5e1; }
.period-time { font-size: 10px; color: #64748b; margin-top: 2px; }
.col-period { width: 90px; }

@media (max-width: 900px) {
  .schedule-table th { font-size: 12px; padding: 10px 4px; }
  .schedule-table th:first-child { width: 64px; }
  .cell-subject { font-size: 12px; }
  .cell-detail { font-size: 10px; }
  .period-name { font-size: 11px; }
  .period-time { font-size: 9px; }
}
@media (max-width: 560px) {
  .schedule-cell { min-height: 56px; padding: 4px; }
  .cell-subject { font-size: 11px; }
  .schedule-table th:first-child { width: 48px; }
}

/* ==================== Print Styles ==================== */
@media print {
  body { background: #fff !important; color: #000 !important; }
  .navbar, .hamburger, .page-loader, .toast-container,
  #btnEditPeriods, #btnPrint, .schedule-table-wrap {
    background: none !important; border: none !important;
  }
  .schedule-table th { background: #e2e8f0; color: #000; }
  .schedule-table td { border-color: #cbd5e1; }
  .schedule-cell { color: #fff !important; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
  .period-cell { background: #f8fafc; }
  .period-name { color: #000; }
  .period-time { color: #64748b; }
  .container { padding: 0; max-width: 100%; }
}

/* Setting page */
.settings-section { margin-bottom: 24px; }
.settings-section h3 { margin-bottom: 12px; }