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

:root {
  --bg: #f5f6fa;
  --surface: #ffffff;
  --border: #e2e8f0;
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --danger: #ef4444;
  --danger-hover: #dc2626;
  --success: #22c55e;
  --text: #1e293b;
  --muted: #64748b;
  --sidebar-w: 220px;
  --radius: 8px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 15px;
  line-height: 1.5;
}

/* Layout */
.layout { display: flex; min-height: 100vh; }

.sidebar {
  width: var(--sidebar-w);
  background: var(--surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  padding: 24px 0;
  position: fixed;
  top: 0; bottom: 0; left: 0;
}

.sidebar-logo {
  font-size: 17px;
  font-weight: 700;
  color: var(--primary);
  padding: 0 20px 24px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 16px;
}

.sidebar nav a {
  display: block;
  padding: 10px 20px;
  color: var(--muted);
  text-decoration: none;
  border-radius: var(--radius);
  margin: 2px 8px;
  font-size: 14px;
}

.sidebar nav a:hover, .sidebar nav a.active {
  background: #eef2ff;
  color: var(--primary);
}

.sidebar-footer {
  margin-top: auto;
  padding: 16px 20px 0;
  border-top: 1px solid var(--border);
}

.sidebar-user { font-size: 13px; color: var(--muted); margin-bottom: 8px; }

/* Background task status bar */
.task-bar { position: relative; margin-bottom: 12px; }
.task-bell {
  position: relative;
  display: flex;
  align-items: center;
  gap: 6px;
  width: 100%;
  padding: 8px 12px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text);
  font-size: 13px;
  cursor: pointer;
}
.task-bell:hover { background: #f8fafc; }
.task-bell-badge {
  background: var(--primary);
  color: #fff;
  font-size: 11px;
  font-weight: 600;
  line-height: 1;
  padding: 3px 6px;
  border-radius: 99px;
}
.task-dropdown {
  position: absolute;
  bottom: calc(100% + 8px);
  left: 0;
  width: 280px;
  max-height: 320px;
  overflow-y: auto;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 8px 24px rgba(0,0,0,.12);
  z-index: 50;
}
.task-dropdown.hidden { display: none; }
.task-dropdown-header {
  padding: 12px 14px;
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: .04em;
  border-bottom: 1px solid var(--border);
}
.task-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border);
  cursor: default;
}
.task-item:last-child { border-bottom: none; }
.task-item[role="button"] { cursor: pointer; }
.task-item[role="button"]:hover { background: #f8fafc; }
.task-item-main { flex: 1; min-width: 0; }
.task-item-label {
  font-size: 13px;
  margin-bottom: 4px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.task-item-dismiss {
  border: none;
  background: transparent;
  color: var(--muted);
  font-size: 16px;
  line-height: 1;
  cursor: pointer;
  padding: 2px 4px;
}
.task-item-dismiss:hover { color: var(--text); }

.main { margin-left: var(--sidebar-w); padding: 32px; flex: 1; max-width: 1100px; }

/* Auth page */
.auth-page {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg);
}

.auth-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px;
  width: 100%;
  max-width: 400px;
}

.auth-card h1 { font-size: 22px; margin-bottom: 6px; }
.auth-card p  { color: var(--muted); margin-bottom: 28px; font-size: 14px; }

/* Forms */
.form-group { margin-bottom: 16px; }
.form-group label { display: block; font-size: 13px; font-weight: 500; margin-bottom: 6px; }
.form-group input:not([type="checkbox"]):not([type="radio"]),
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 9px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 14px;
  color: var(--text);
  outline: none;
  transition: border-color .15s;
}
.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus { border-color: var(--primary); }
.form-group textarea { min-height: 100px; resize: vertical; }

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 9px 18px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  border: none;
  text-decoration: none;
  transition: background .15s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-hover); }
.btn-danger  { background: var(--danger); color: #fff; }
.btn-danger:hover { background: var(--danger-hover); }
.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--primary);
}
.btn-outline:hover { background: #eef2ff; }
.btn-sm { padding: 5px 12px; font-size: 13px; }
.btn:disabled { opacity: .6; cursor: not-allowed; }
.btn-full { width: 100%; justify-content: center; }

/* Page header */
.page-header { display: flex; align-items: center; justify-content: space-between; margin-bottom: 28px; }
.page-header h1 { font-size: 22px; font-weight: 700; }

/* Cards / Tables */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 20px;
}

.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; }
th, td { padding: 11px 14px; text-align: left; border-bottom: 1px solid var(--border); font-size: 14px; }
th { font-weight: 600; color: var(--muted); font-size: 12px; text-transform: uppercase; letter-spacing: .04em; }
tr:last-child td { border-bottom: none; }
tr:hover td { background: #f8fafc; }
.row-clickable { cursor: pointer; }

/* Stats grid */
.stats-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 16px; margin-bottom: 28px; }
.stat-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
}
.stat-card .label { font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: .04em; margin-bottom: 6px; }
.stat-card .value { font-size: 28px; font-weight: 700; color: var(--primary); }

/* Progress bar */
.progress-bar { height: 8px; background: #e2e8f0; border-radius: 99px; overflow: hidden; }
.progress-fill { height: 100%; background: var(--primary); border-radius: 99px; transition: width .3s; }

/* Badge */
.badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 99px;
  font-size: 12px;
  font-weight: 500;
}
.badge-green { background: #dcfce7; color: #166534; }
.badge-gray  { background: #f1f5f9; color: var(--muted); }
.badge-blue  { background: #dbeafe; color: #1d4ed8; }
.badge-red   { background: #fee2e2; color: #991b1b; }

/* Lesson type tabs */
.tabs { display: flex; gap: 8px; margin-bottom: 16px; }
.tab {
  padding: 6px 16px;
  border-radius: 99px;
  font-size: 13px;
  cursor: pointer;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--muted);
}
.tab.active { background: var(--primary); color: #fff; border-color: var(--primary); }

/* Video embed */
.video-wrapper {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  border-radius: var(--radius);
  overflow: hidden;
  background: #000;
  margin-bottom: 20px;
}
.video-wrapper iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: none; }

/* Alert */
.alert {
  padding: 12px 16px;
  border-radius: var(--radius);
  font-size: 14px;
  margin-bottom: 16px;
}
.alert-error { background: #fef2f2; color: #991b1b; border: 1px solid #fecaca; }
.alert-success { background: #f0fdf4; color: #166534; border: 1px solid #bbf7d0; }

/* Lesson list (course editor) */
.lesson-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 8px;
  background: var(--surface);
}
.lesson-item .lesson-title { flex: 1; font-size: 14px; }
.lesson-item .lesson-type { font-size: 12px; color: var(--muted); }

/* Quiz editor */
.question-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 12px;
  background: var(--surface);
}
.question-card .q-num { font-size: 12px; color: var(--muted); margin-bottom: 8px; }

/* Modal */
.modal-overlay {
  position: fixed; inset: 0;
  background: rgba(0,0,0,.4);
  display: flex; align-items: center; justify-content: center;
  z-index: 100;
}
.modal-overlay.hidden { display: none; }
.modal {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 28px;
  width: 100%;
  max-width: 520px;
  max-height: 90vh;
  overflow-y: auto;
}
.modal h2 { font-size: 18px; margin-bottom: 20px; }

.empty { text-align: center; padding: 48px; color: var(--muted); font-size: 14px; }