/* ==========================================================================
   AdCendes Learn — Stylesheet v3 (polished + themeable)
   Sections:
     1. Reset + base
     2. Theme tokens (light + dark)
     3. User preferences (font scale, density, reading width, font family)
     4. Animations + keyframes
     5. Login
     6. Sidebar
     7. Topbar + admin bar
     8. Content / welcome / cards
     9. Lesson view
    10. Editor
    11. Settings drawer
    12. Buttons + utilities
    13. Mobile
    14. Print
   ========================================================================== */

/* 1. Reset + base
   ------------------------------------------------------------------------ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
button { font-family: inherit; cursor: pointer; }
[hidden] { display: none !important; }
input, textarea, select { font-family: inherit; }

/* 2. Theme tokens
   ------------------------------------------------------------------------ */
:root {
  --bg: #F6F8FB;
  --surface: #FFF;
  --surface2: #FAFBFC;
  --hover: #F0F2F5;
  --border: #E4E8EE;
  --border2: #EEF0F4;

  --blue: #2D6BE4;   --blue-l: #E8F0FE;   --blue-d: #1A4FC0;
  --green: #18A558;  --green-l: #E6F7EE;
  --red: #E43D3D;    --red-l: #FDEDED;
  --orange: #E4901E; --orange-l: #FDF3E3;
  --purple: #7C4DDB; --purple-l: #F0EAFA;

  --text: #18202C;
  --text2: #4A5568;
  --text3: #8896AA;
  --text4: #B8C4D4;

  --radius: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow: 0 1px 3px rgba(15, 23, 42, 0.06), 0 1px 2px rgba(15, 23, 42, 0.03);
  --shadow-md: 0 4px 16px rgba(15, 23, 42, 0.08), 0 2px 4px rgba(15, 23, 42, 0.04);
  --shadow-lg: 0 12px 32px rgba(15, 23, 42, 0.12), 0 4px 8px rgba(15, 23, 42, 0.06);
  --shadow-xl: 0 24px 48px rgba(15, 23, 42, 0.16), 0 8px 16px rgba(15, 23, 42, 0.08);

  --font: 'Inter', system-ui, -apple-system, sans-serif;
  --font-serif: 'Lora', 'Georgia', serif;
  --mono: 'JetBrains Mono', monospace;
  --reading-font: var(--font);

  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out: cubic-bezier(0.4, 0, 0.2, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);

  --font-scale: 1;
  --density: 1;
  --reading-width: 900px;
}

[data-theme="dark"] {
  --bg: #0F1419;
  --surface: #18202C;
  --surface2: #1F2937;
  --hover: #283242;
  --border: #2D3848;
  --border2: #232C3A;

  --blue: #4F8AF7;   --blue-l: rgba(79, 138, 247, 0.15);   --blue-d: #7BA5FA;
  --green: #34D17B;  --green-l: rgba(52, 209, 123, 0.15);
  --red: #F26565;    --red-l: rgba(242, 101, 101, 0.15);
  --orange: #F0A848; --orange-l: rgba(240, 168, 72, 0.15);
  --purple: #9F7BE6; --purple-l: rgba(159, 123, 230, 0.15);

  --text: #F1F5F9;
  --text2: #CBD5E1;
  --text3: #94A3B8;
  --text4: #64748B;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4), 0 2px 4px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5), 0 4px 8px rgba(0, 0, 0, 0.3);
  --shadow-xl: 0 24px 48px rgba(0, 0, 0, 0.6), 0 8px 16px rgba(0, 0, 0, 0.4);
}

body {
  font-family: var(--font);
  font-size: calc(14px * var(--font-scale));
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color 0.3s var(--ease-in-out), color 0.3s var(--ease-in-out);
}

::selection { background: var(--blue-l); color: var(--blue-d); }

::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: var(--text4);
  border-radius: 4px;
  border: 2px solid var(--bg);
  transition: background 0.2s var(--ease-out);
}
::-webkit-scrollbar-thumb:hover { background: var(--text3); }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
  html { scroll-behavior: auto; }
}

/* 3. User preferences
   ------------------------------------------------------------------------ */
[data-font-scale="xs"]  { --font-scale: 0.875; }
[data-font-scale="sm"]  { --font-scale: 0.9375; }
[data-font-scale="md"]  { --font-scale: 1; }
[data-font-scale="lg"]  { --font-scale: 1.0625; }
[data-font-scale="xl"]  { --font-scale: 1.125; }

[data-density="compact"]     { --density: 0.85; }
[data-density="comfortable"] { --density: 1; }
[data-density="spacious"]    { --density: 1.15; }

[data-width="narrow"]  { --reading-width: 700px; }
[data-width="default"] { --reading-width: 900px; }
[data-width="wide"]    { --reading-width: 1100px; }
[data-width="full"]    { --reading-width: 100%; }

[data-reading-font="serif"] { --reading-font: var(--font-serif); }

/* 4. Animations
   ------------------------------------------------------------------------ */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes slideInDown {
  from { opacity: 0; transform: translateY(-6px); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}
.fade-in { animation: fadeIn 0.35s var(--ease-out); }

/* 5. Login
   ------------------------------------------------------------------------ */
.login {
  position: fixed; inset: 0;
  background:
    radial-gradient(circle at 20% 20%, var(--blue-l) 0%, transparent 50%),
    radial-gradient(circle at 80% 80%, var(--purple-l) 0%, transparent 50%),
    var(--bg);
  display: flex; align-items: center; justify-content: center;
  z-index: 999;
  animation: fadeIn 0.5s var(--ease-out);
}
.login-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 48px 44px;
  max-width: 400px; width: 92%;
  box-shadow: var(--shadow-xl);
  text-align: center;
  animation: slideInDown 0.5s var(--ease-spring) 0.1s both;
}
.login-brand {
  font-size: 11px; font-weight: 800;
  color: var(--blue);
  letter-spacing: 3px; text-transform: uppercase;
}
.login-card h2 {
  font-size: 26px; font-weight: 800;
  margin: 8px 0 4px;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, var(--blue), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.login-card p {
  font-size: 13px; color: var(--text3);
  margin-bottom: 28px;
}
.login-input {
  width: 100%;
  padding: 12px 16px;
  border-radius: var(--radius);
  border: 1.5px solid var(--border);
  background: var(--surface2);
  color: var(--text);
  font-size: 14px;
  outline: 0;
  margin-bottom: 10px;
  transition: border-color 0.2s var(--ease-out), box-shadow 0.2s var(--ease-out);
}
.login-input:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 4px var(--blue-l);
}
.login-btn {
  width: 100%;
  padding: 13px;
  border-radius: var(--radius);
  border: 0;
  background: linear-gradient(135deg, var(--blue), var(--blue-d));
  color: #fff;
  font: 700 14px var(--font);
  transition: all 0.2s var(--ease-out);
  margin-top: 8px;
  letter-spacing: 0.3px;
  position: relative;
  overflow: hidden;
}
.login-btn::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, transparent, rgba(255,255,255,0.2), transparent);
  transform: translateX(-100%);
  transition: transform 0.6s var(--ease-out);
}
.login-btn:hover::before { transform: translateX(100%); }
.login-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(45, 107, 228, 0.3);
}
.login-btn:active { transform: translateY(0); }
.login-err {
  color: var(--red);
  font-size: 12px;
  margin-top: 10px;
  display: none;
  animation: slideInDown 0.3s var(--ease-out);
}
.login-err.show { display: block; }

/* 6. Shell + sidebar
   ------------------------------------------------------------------------ */
.shell { display: flex; min-height: 100vh; }

.sidebar {
  width: 280px;
  background: var(--surface);
  border-right: 1px solid var(--border);
  display: flex; flex-direction: column;
  position: fixed; top: 0; bottom: 0;
  z-index: 40;
  transition: transform 0.35s var(--ease-out);
}

/* Auto-hide mode (desktop only — mobile already auto-hides) */
@media (min-width: 901px) {
  [data-sidebar="autohide"] .sidebar {
    transform: translateX(calc(-100% + 8px));
    box-shadow: var(--shadow-md);
  }
  /* Thin peek strip on the left edge — colored hint that sidebar is hiding */
  [data-sidebar="autohide"] .sidebar::after {
    content: '';
    position: absolute;
    top: 0; right: -4px; bottom: 0;
    width: 4px;
    background: linear-gradient(180deg, var(--blue), var(--purple));
    opacity: 0.6;
    border-radius: 0 4px 4px 0;
    transition: opacity 0.25s var(--ease-out);
  }
  [data-sidebar="autohide"] .sidebar:hover {
    transform: translateX(0);
    box-shadow: var(--shadow-xl);
  }
  [data-sidebar="autohide"] .sidebar:hover::after {
    opacity: 0;
  }
  /* When hidden, give main content the full width */
  [data-sidebar="autohide"] .main {
    margin-left: 8px;
  }
  /* Wider hit area along the left edge for easier triggering */
  [data-sidebar="autohide"] .sidebar::before {
    content: '';
    position: absolute;
    top: 0; right: -20px; bottom: 0;
    width: 20px;
  }
  /* Sidebar stays open while mouse is anywhere over it OR the peek strip */
  [data-sidebar="autohide"] .sidebar.pinned {
    transform: translateX(0);
  }
}
.sidebar-brand {
  padding: 20px;
  border-bottom: 1px solid var(--border2);
}
.sidebar-brand-text {
  font-size: 10px; font-weight: 800;
  color: var(--blue);
  letter-spacing: 2.5px; text-transform: uppercase;
}
.sidebar-brand-title {
  font-size: 17px; font-weight: 800;
  letter-spacing: -0.3px;
  margin-top: 2px;
}
.sidebar-scroll {
  flex: 1;
  overflow-y: auto;
  padding: 12px 10px;
}
.sidebar-footer {
  padding: 14px 16px;
  border-top: 1px solid var(--border2);
  background: var(--surface2);
}
.sidebar-user {
  font-size: 12px; font-weight: 600;
  color: var(--text2);
  display: flex; align-items: center;
  gap: 8px;
  margin-bottom: 10px;
}
.sidebar-user .role {
  font-size: 9px; font-weight: 700;
  padding: 2px 6px;
  border-radius: 4px;
  text-transform: uppercase; letter-spacing: .5px;
}
.sidebar-footer-actions {
  display: flex;
  gap: 6px;
}

.avatar {
  display: inline-flex; align-items: center; justify-content: center;
  border-radius: 50%;
  font-weight: 800; text-transform: uppercase;
  flex-shrink: 0;
  letter-spacing: 0.5px;
  transition: transform 0.2s var(--ease-spring);
}
.avatar:hover { transform: scale(1.08); }
.avatar-sm { width: 26px; height: 26px; font-size: 10px; }
.avatar-md { width: 32px; height: 32px; font-size: 11px; }

.role-admin  { background: var(--blue-l);  color: var(--blue); }
.role-lead   { background: var(--green-l); color: var(--green); }
.role-member { background: var(--bg);      color: var(--text3); }

.icon-only-btn {
  font: 600 13px var(--font);
  color: var(--text3);
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 7px 10px;
  border-radius: 7px;
  transition: all 0.2s var(--ease-out);
  display: inline-flex; align-items: center; justify-content: center;
}
.icon-only-btn:hover {
  border-color: var(--blue);
  color: var(--blue);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}
.logout-btn {
  flex: 1;
  font: 600 11px var(--font);
  color: var(--text3);
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 7px 12px;
  border-radius: 7px;
  transition: all 0.2s var(--ease-out);
}
.logout-btn:hover {
  border-color: var(--red);
  color: var(--red);
  background: var(--red-l);
}

/* Tree */
.course-item {
  margin-bottom: 6px;
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--surface2);
  border: 1px solid var(--border2);
  transition: border-color 0.2s var(--ease-out), box-shadow 0.2s var(--ease-out);
}
.course-item:hover {
  border-color: var(--border);
  box-shadow: var(--shadow-sm);
}
.course-item.open {
  border-color: var(--blue);
}
.course-head {
  padding: calc(11px * var(--density)) 12px;
  display: flex; align-items: center;
  gap: 8px;
  cursor: pointer;
  font-size: 13px; font-weight: 700;
  color: var(--text);
  position: relative;
  transition: background 0.2s var(--ease-out);
}
.course-head::before {
  content: '';
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 3px;
  background: var(--blue);
  opacity: 0;
  transition: opacity 0.2s var(--ease-out);
}
.course-head:hover { background: var(--hover); }
.course-head:hover::before { opacity: 0.5; }
.course-head.open::before { opacity: 1; }

.course-head .chev,
.module-head .chev {
  margin-left: auto;
  font-size: 11px;
  color: var(--text3);
  transition: transform 0.25s var(--ease-out);
}
.course-head.open .chev,
.module-head.open .chev { transform: rotate(90deg); }
.course-icon { font-size: 16px; }

.module-list {
  padding: 4px 8px 8px;
  animation: fadeIn 0.25s var(--ease-out);
}
.module-item { margin-bottom: 2px; }
.module-head {
  padding: calc(7px * var(--density)) 8px;
  display: flex; align-items: center;
  gap: 6px;
  cursor: pointer;
  font-size: 12px; font-weight: 600;
  color: var(--text2);
  border-radius: 6px;
  transition: background 0.2s var(--ease-out), color 0.2s var(--ease-out);
}
.module-head:hover { background: var(--hover); color: var(--text); }
.module-head .chev { font-size: 10px; }

.lesson-list {
  padding: 2px 0 4px 16px;
  animation: fadeIn 0.25s var(--ease-out);
}
.lesson-link {
  padding: calc(7px * var(--density)) 10px;
  border-radius: 6px;
  font-size: 12px;
  color: var(--text2);
  cursor: pointer;
  display: flex; align-items: center;
  gap: 8px;
  transition: all 0.18s var(--ease-out);
  margin-bottom: 1px;
  position: relative;
}
.lesson-link:hover {
  background: var(--hover);
  color: var(--text);
  transform: translateX(2px);
}
.lesson-link.active {
  background: var(--blue-l);
  color: var(--blue-d);
  font-weight: 600;
  transform: translateX(2px);
}
.lesson-link .dot {
  width: 7px; height: 7px;
  border-radius: 50%;
  background: var(--text4);
  flex-shrink: 0;
  transition: background 0.2s var(--ease-out), transform 0.2s var(--ease-spring), box-shadow 0.2s var(--ease-out);
}
.lesson-link:hover .dot { transform: scale(1.3); }
.lesson-link.read .dot {
  background: var(--green);
  box-shadow: 0 0 0 3px var(--green-l);
}
.lesson-link.active .dot { background: var(--blue); }

.tree-label {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.tree-empty {
  font-size: 11px;
  color: var(--text3);
  padding: 8px 12px;
  font-style: italic;
}

.sidebar-actions {
  padding: 8px 10px;
  border-top: 1px solid var(--border2);
}
.btn-add {
  width: 100%;
  padding: 8px 12px;
  border-radius: 6px;
  background: var(--blue-l);
  color: var(--blue-d);
  border: 1px dashed var(--blue);
  font: 700 11px var(--font);
  display: flex; align-items: center; justify-content: center;
  gap: 6px;
  transition: all 0.2s var(--ease-out);
}
.btn-add:hover {
  background: var(--blue);
  color: #fff;
  border-style: solid;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(45, 107, 228, 0.25);
}
.btn-add.compact { font-size: 10px; padding: 6px 10px; margin: 6px 4px 4px; }
.btn-add.compact-sm { font-size: 10px; padding: 5px 10px; margin: 6px 6px 4px; }

.edit-actions {
  display: flex;
  gap: 4px;
  opacity: 0;
  transition: opacity 0.2s var(--ease-out);
}
.course-head:hover .edit-actions,
.module-head:hover .edit-actions,
.lesson-link:hover .edit-actions { opacity: 1; }

.icon-btn {
  width: 26px; height: 26px;
  border-radius: 5px;
  border: 0; background: 0;
  color: var(--text3);
  display: inline-flex; align-items: center; justify-content: center;
  transition: all 0.15s var(--ease-out);
  font-size: 13px;
}
.icon-btn:hover {
  background: var(--hover);
  color: var(--text);
  transform: scale(1.1);
}
.icon-btn.danger:hover {
  background: var(--red-l);
  color: var(--red);
}
.icon-btn.xs { width: 18px; height: 18px; font-size: 10px; }

/* 7. Topbar
   ------------------------------------------------------------------------ */
.main {
  margin-left: 280px;
  flex: 1;
  min-height: 100vh;
  display: flex; flex-direction: column;
}
.topbar {
  padding: 14px 32px;
  border-bottom: 1px solid var(--border2);
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  display: flex; align-items: center; justify-content: space-between;
  gap: 12px;
  position: sticky; top: 0;
  z-index: 30;
}
.crumbs {
  font-size: 12px;
  color: var(--text3);
  display: flex; align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}
.crumbs .sep { color: var(--text4); }
.crumbs .cur { color: var(--text); font-weight: 600; }
.crumbs .clickable {
  cursor: pointer;
  transition: color 0.15s var(--ease-out);
}
.crumbs .clickable:hover { color: var(--blue); }

.search {
  padding: 8px 14px;
  border-radius: var(--radius);
  border: 1.5px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font: 400 12px var(--font);
  outline: 0;
  width: 240px;
  transition: all 0.2s var(--ease-out);
}
.search:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 4px var(--blue-l);
  width: 280px;
}

.topbar-actions { display: flex; align-items: center; gap: 8px; }

.topbar-icon-btn {
  width: 34px; height: 34px;
  border-radius: 8px;
  border: 1.5px solid var(--border);
  background: var(--surface);
  color: var(--text2);
  display: inline-flex; align-items: center; justify-content: center;
  transition: all 0.2s var(--ease-out);
  font-size: 15px;
}
.topbar-icon-btn:hover {
  border-color: var(--blue);
  color: var(--blue);
  background: var(--blue-l);
  transform: translateY(-1px);
}

.sync {
  display: inline-flex; align-items: center;
  gap: 5px;
  font-size: 10px; font-weight: 600;
  padding: 4px 10px;
  border-radius: 20px;
}
.sync.ok  { background: var(--green-l);  color: var(--green); }
.sync.off { background: var(--orange-l); color: var(--orange); animation: pulse 1.5s infinite; }
.sync::before {
  content: '';
  width: 6px; height: 6px;
  border-radius: 50%;
}
.sync.ok::before  { background: var(--green); }
.sync.off::before { background: var(--orange); }

.content {
  flex: 1;
  padding: calc(32px * var(--density)) 40px 80px;
  max-width: var(--reading-width);
  width: 100%;
  margin: 0 auto;
  animation: fadeIn 0.35s var(--ease-out);
}

/* Admin bar */
.admin-bar {
  background: linear-gradient(90deg, var(--blue-l), color-mix(in srgb, var(--purple-l) 60%, transparent));
  border-bottom: 1px solid var(--blue);
  padding: 10px 32px;
  display: flex; align-items: center; justify-content: space-between;
  font-size: 12px; font-weight: 600;
  color: var(--blue-d);
}
.admin-bar .toggle { display: flex; align-items: center; gap: 10px; }
.admin-bar-hint { font-size: 11px; color: var(--text3); font-weight: 500; }

.switch {
  position: relative;
  width: 38px; height: 22px;
  background: var(--text4);
  border-radius: 11px;
  cursor: pointer;
  transition: background 0.25s var(--ease-out);
}
.switch.on { background: var(--blue); }
.switch::after {
  content: '';
  position: absolute;
  top: 2px; left: 2px;
  width: 18px; height: 18px;
  background: #fff;
  border-radius: 50%;
  transition: transform 0.25s var(--ease-spring);
  box-shadow: 0 2px 4px rgba(0,0,0,.2);
}
.switch.on::after { transform: translateX(16px); }

/* 8. Welcome / cards
   ------------------------------------------------------------------------ */
.welcome {
  text-align: center;
  padding: 60px 20px;
}
.welcome-icon {
  font-size: 64px;
  margin-bottom: 16px;
  display: inline-block;
  animation: slideInDown 0.6s var(--ease-spring);
}
.welcome h1 {
  font-size: calc(32px * var(--font-scale));
  font-weight: 800;
  letter-spacing: -0.6px;
  margin-bottom: 8px;
  background: linear-gradient(135deg, var(--text), var(--blue));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.welcome p {
  font-size: 14px; color: var(--text3);
  max-width: 480px;
  margin: 0 auto 28px;
}
.welcome-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  max-width: 720px;
  margin: 0 auto;
  text-align: left;
}
.welcome-card {
  background: var(--surface);
  border: 1px solid var(--border2);
  border-radius: var(--radius-lg);
  padding: 20px;
  cursor: pointer;
  transition: all 0.25s var(--ease-out);
  position: relative;
  overflow: hidden;
}
.welcome-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--blue), var(--purple));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s var(--ease-out);
}
.welcome-card:hover {
  border-color: transparent;
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}
.welcome-card:hover::before { transform: scaleX(1); }
.welcome-card .ico {
  font-size: 28px;
  margin-bottom: 10px;
  display: inline-block;
  transition: transform 0.3s var(--ease-spring);
}
.welcome-card:hover .ico { transform: scale(1.15) rotate(-5deg); }
.welcome-card h3 { font-size: 15px; font-weight: 700; margin-bottom: 4px; }
.welcome-card p {
  font-size: 12px; color: var(--text3);
  margin: 0;
  max-width: none;
}

.empty {
  text-align: center;
  padding: 50px 20px;
  color: var(--text3);
}
.empty.tight { padding: 30px 16px; }
.empty-icon { font-size: 42px; margin-bottom: 12px; opacity: .5; }
.empty-title { font-size: 14px; font-weight: 600; color: var(--text2); margin-bottom: 4px; }
.empty-sub { font-size: 12px; }

/* 9. Lesson view
   ------------------------------------------------------------------------ */
.lesson-header {
  margin-bottom: 28px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border2);
  animation: slideInDown 0.4s var(--ease-out);
}
.lesson-eyebrow {
  font-size: 11px; font-weight: 700;
  color: var(--blue);
  text-transform: uppercase; letter-spacing: 1.5px;
  margin-bottom: 8px;
}
.lesson-title {
  font-size: calc(32px * var(--font-scale));
  font-weight: 800;
  letter-spacing: -0.6px;
  line-height: 1.2;
  margin-bottom: 12px;
}
.lesson-meta {
  font-size: 12px; color: var(--text3);
  display: flex; align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}
.lesson-meta .pill {
  padding: 3px 10px;
  border-radius: 12px;
  background: var(--bg);
  font-weight: 600;
}

.lesson-body {
  font-family: var(--reading-font);
  font-size: calc(15px * var(--font-scale));
  line-height: 1.75;
  color: var(--text2);
}
.lesson-body h1 {
  font-size: calc(26px * var(--font-scale));
  font-weight: 800;
  margin: 36px 0 14px;
  color: var(--text);
  letter-spacing: -0.3px;
  font-family: var(--font);
}
.lesson-body h2 {
  font-size: calc(21px * var(--font-scale));
  font-weight: 800;
  margin: 30px 0 12px;
  color: var(--text);
  letter-spacing: -0.2px;
  font-family: var(--font);
}
.lesson-body h3 {
  font-size: calc(17px * var(--font-scale));
  font-weight: 700;
  margin: 24px 0 10px;
  color: var(--text);
  font-family: var(--font);
}
.lesson-body p { margin-bottom: 16px; }
.lesson-body ul, .lesson-body ol { margin: 0 0 16px 24px; }
.lesson-body li { margin-bottom: 6px; }
.lesson-body strong { color: var(--text); font-weight: 700; }
.lesson-body em { font-style: italic; }
.lesson-body a {
  color: var(--blue);
  text-decoration: none;
  background-image: linear-gradient(var(--blue), var(--blue));
  background-size: 0 1.5px;
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: background-size 0.3s var(--ease-out);
  padding-bottom: 2px;
}
.lesson-body a:hover { background-size: 100% 1.5px; }
.lesson-body code {
  font-family: var(--mono);
  font-size: 0.875em;
  background: var(--bg);
  padding: 2px 7px;
  border-radius: 5px;
  color: var(--text);
  border: 1px solid var(--border2);
}
.lesson-body pre {
  background: #0F1419;
  color: #E4E8EE;
  padding: 16px 20px;
  border-radius: var(--radius-lg);
  overflow-x: auto;
  margin: 18px 0;
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.65;
  box-shadow: var(--shadow);
}
.lesson-body pre code { background: 0; border: 0; color: inherit; padding: 0; font-size: inherit; }
.lesson-body blockquote {
  border-left: 4px solid var(--blue);
  padding: 12px 20px;
  margin: 18px 0;
  background: var(--blue-l);
  border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
  color: var(--text2);
  font-style: italic;
}
.lesson-body img {
  max-width: 100%;
  border-radius: var(--radius-lg);
  margin: 18px 0;
  border: 1px solid var(--border2);
  box-shadow: var(--shadow);
  transition: transform 0.3s var(--ease-out), box-shadow 0.3s var(--ease-out);
}
.lesson-body img:hover {
  transform: scale(1.01);
  box-shadow: var(--shadow-md);
}
.lesson-body hr {
  border: 0;
  border-top: 1px solid var(--border2);
  margin: 28px 0;
}

.lesson-body .callout {
  padding: 16px 20px;
  border-radius: var(--radius-lg);
  margin: 18px 0;
  font-size: 14px;
  display: flex; gap: 12px;
  align-items: flex-start;
  box-shadow: var(--shadow-sm);
}
.lesson-body .callout-info   { background: var(--blue-l);   color: var(--blue-d);  border-left: 4px solid var(--blue); }
.lesson-body .callout-warn   { background: var(--orange-l); color: #8C5A0F;        border-left: 4px solid var(--orange); }
.lesson-body .callout-tip    { background: var(--green-l);  color: #0A6E3C;        border-left: 4px solid var(--green); }
.lesson-body .callout-danger { background: var(--red-l);    color: #9B2424;        border-left: 4px solid var(--red); }
[data-theme="dark"] .lesson-body .callout-warn   { color: var(--orange); }
[data-theme="dark"] .lesson-body .callout-tip    { color: var(--green); }
[data-theme="dark"] .lesson-body .callout-danger { color: var(--red); }

.video-wrap {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  margin: 18px 0;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: #000;
  box-shadow: var(--shadow-md);
}
.video-wrap iframe {
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  border: 0;
}

.lesson-footer {
  margin-top: 48px;
  padding-top: 28px;
  border-top: 1px solid var(--border2);
  display: flex; justify-content: space-between; align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}
.lesson-nav { display: flex; gap: 8px; }
.nav-btn {
  padding: 11px 16px;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1.5px solid var(--border);
  color: var(--text2);
  font: 600 12px var(--font);
  transition: all 0.2s var(--ease-out);
  display: inline-flex; align-items: center;
  gap: 6px;
}
.nav-btn:hover:not(:disabled) {
  border-color: var(--blue);
  color: var(--blue);
  background: var(--blue-l);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}
.nav-btn:disabled { opacity: .4; cursor: not-allowed; }

.mark-btn {
  padding: 10px 18px;
  border-radius: var(--radius);
  border: 1.5px solid var(--green);
  background: var(--surface);
  color: var(--green);
  font: 700 12px var(--font);
  transition: all 0.2s var(--ease-out);
  display: inline-flex; align-items: center;
  gap: 6px;
}
.mark-btn:hover {
  background: var(--green);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(24, 165, 88, 0.25);
}
.mark-btn.done {
  background: var(--green);
  color: #fff;
  box-shadow: var(--shadow-sm);
}

.lesson-edit-bar {
  display: flex;
  gap: 6px;
  margin-bottom: 16px;
}

/* 10. Editor
   ------------------------------------------------------------------------ */
.editor-shell {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: 20px;
  box-shadow: var(--shadow);
  animation: fadeIn 0.3s var(--ease-out);
}
.editor-head {
  padding: 14px 20px;
  background: linear-gradient(90deg, var(--blue-l), color-mix(in srgb, var(--purple-l) 50%, transparent));
  color: var(--blue-d);
  font: 700 12px var(--font);
  display: flex; align-items: center; justify-content: space-between;
}
.editor-tabs {
  display: flex;
  border-bottom: 1px solid var(--border2);
  background: var(--surface2);
}
.editor-tab {
  padding: 11px 20px;
  font: 600 12px var(--font);
  color: var(--text3);
  border: 0;
  background: 0;
  border-bottom: 2px solid transparent;
  transition: all 0.2s var(--ease-out);
}
.editor-tab:hover { color: var(--text2); background: var(--hover); }
.editor-tab.active {
  color: var(--blue);
  border-bottom-color: var(--blue);
  background: var(--surface);
}
.editor-tab-hint {
  margin-left: auto;
  padding: 8px 14px;
  font-size: 11px;
  color: var(--text3);
  align-self: center;
}

.editor-fields {
  padding: 20px;
  display: grid;
  gap: 14px;
  border-bottom: 1px solid var(--border2);
}
.field { display: flex; flex-direction: column; gap: 6px; }
.field label {
  font-size: 11px; font-weight: 700;
  color: var(--text3);
  text-transform: uppercase; letter-spacing: .5px;
}
.field input, .field textarea, .field select {
  padding: 10px 13px;
  border-radius: var(--radius);
  border: 1.5px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font: 400 13px var(--font);
  outline: 0;
  transition: all 0.2s var(--ease-out);
  width: 100%;
}
.field input:focus, .field textarea:focus, .field select:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 4px var(--blue-l);
}
.field textarea {
  resize: vertical;
  min-height: 60px;
  font-size: 13px;
  line-height: 1.6;
}
.field-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

.editor-content { padding: 20px; }
.editor-textarea {
  width: 100%;
  min-height: 400px;
  padding: 16px;
  border-radius: var(--radius);
  border: 1.5px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font: 400 13px var(--mono);
  outline: 0;
  resize: vertical;
  line-height: 1.7;
  transition: all 0.2s var(--ease-out);
}
.editor-textarea:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 4px var(--blue-l);
}

.editor-preview {
  padding: 20px 24px;
  min-height: 400px;
  background: var(--surface2);
  border-radius: var(--radius);
  border: 1.5px dashed var(--border);
}

.editor-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  padding: 10px 14px;
  background: var(--surface2);
  border-bottom: 1px solid var(--border2);
}
.tool-btn {
  padding: 6px 11px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  font: 600 11px var(--font);
  color: var(--text2);
  transition: all 0.15s var(--ease-out);
}
.tool-btn:hover {
  background: var(--blue-l);
  color: var(--blue);
  border-color: var(--blue);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.editor-footer {
  padding: 14px 20px;
  background: var(--surface2);
  border-top: 1px solid var(--border2);
  display: flex; justify-content: flex-end;
  gap: 8px;
  align-items: center;
}
.editor-msg {
  font-size: 12px;
  margin-right: auto;
}
.editor-msg.ok  { color: var(--green); }
.editor-msg.err { color: var(--red); }

/* 11. Settings drawer
   ------------------------------------------------------------------------ */
.drawer-bg {
  position: fixed;
  inset: 0;
  background: rgba(15, 20, 25, 0.4);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  z-index: 90;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s var(--ease-out);
}
.drawer-bg.open {
  opacity: 1;
  pointer-events: auto;
}

.drawer {
  position: fixed;
  top: 0; right: 0; bottom: 0;
  width: 380px;
  max-width: 92vw;
  background: var(--surface);
  border-left: 1px solid var(--border);
  z-index: 91;
  transform: translateX(100%);
  transition: transform 0.35s var(--ease-out);
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-xl);
}
.drawer.open { transform: translateX(0); }

.drawer-head {
  padding: 20px 24px;
  border-bottom: 1px solid var(--border2);
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.drawer-head h3 {
  font-size: 18px;
  font-weight: 800;
  letter-spacing: -0.3px;
}
.drawer-close {
  width: 32px; height: 32px;
  border-radius: 8px;
  border: 0;
  background: var(--surface2);
  color: var(--text2);
  font-size: 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s var(--ease-out);
}
.drawer-close:hover {
  background: var(--hover);
  color: var(--text);
  transform: rotate(90deg);
}

.drawer-body {
  flex: 1;
  overflow-y: auto;
  padding: 8px 0;
}

.setting-group {
  padding: 18px 24px;
  border-bottom: 1px solid var(--border2);
}
.setting-group:last-child { border-bottom: 0; }
.setting-label {
  font-size: 11px;
  font-weight: 700;
  color: var(--text3);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 10px;
}
.setting-desc {
  font-size: 12px;
  color: var(--text3);
  margin-top: 6px;
  line-height: 1.5;
}

.segmented {
  display: flex;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 3px;
  gap: 2px;
}
.segmented button {
  flex: 1;
  padding: 8px 6px;
  border: 0;
  background: transparent;
  border-radius: 6px;
  font: 600 12px var(--font);
  color: var(--text3);
  transition: all 0.2s var(--ease-out);
}
.segmented button:hover { color: var(--text2); }
.segmented button.active {
  background: var(--surface);
  color: var(--blue);
  box-shadow: var(--shadow-sm);
}

.toggle-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
}
.toggle-row-text { flex: 1; }
.toggle-row-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--text);
}
.toggle-row-sub {
  font-size: 12px;
  color: var(--text3);
  margin-top: 2px;
}

.font-preview {
  margin-top: 10px;
  padding: 12px 14px;
  background: var(--surface2);
  border-radius: var(--radius);
  border: 1px solid var(--border2);
  font-size: calc(15px * var(--font-scale));
  color: var(--text2);
  line-height: 1.6;
  font-family: var(--reading-font);
}

.drawer-footer {
  padding: 14px 24px;
  border-top: 1px solid var(--border2);
  background: var(--surface2);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
}

/* 12. Buttons + utilities
   ------------------------------------------------------------------------ */
.btn {
  padding: 9px 16px;
  border-radius: var(--radius);
  border: 0;
  background: var(--blue);
  color: #fff;
  font: 600 12px var(--font);
  transition: all 0.2s var(--ease-out);
  display: inline-flex; align-items: center;
  gap: 6px;
  position: relative;
  overflow: hidden;
}
.btn:hover {
  background: var(--blue-d);
  transform: translateY(-1px);
  box-shadow: 0 6px 14px rgba(45, 107, 228, 0.25);
}
.btn:active { transform: translateY(0); }
.btn.sec {
  background: var(--surface);
  color: var(--text2);
  border: 1.5px solid var(--border);
}
.btn.sec:hover {
  background: var(--hover);
  color: var(--text);
  box-shadow: var(--shadow-sm);
}
.btn.danger { background: var(--red); }
.btn.danger:hover { background: #C72E2E; box-shadow: 0 6px 14px rgba(228, 61, 61, 0.25); }
.btn.sm    { padding: 6px 12px; font-size: 11px; }
.btn.ghost { background: 0; color: var(--text3); padding: 7px 12px; }
.btn.ghost:hover {
  background: var(--hover);
  color: var(--text);
  box-shadow: none;
  transform: none;
}
.btn.lesson-edit-bar [data-action="delete-lesson"] { color: var(--red); }

.mobile-toggle {
  display: none;
  background: var(--blue);
  color: #fff;
  border: 0;
  width: 38px; height: 38px;
  border-radius: 8px;
  font-size: 18px;
  align-items: center; justify-content: center;
  transition: all 0.2s var(--ease-out);
}
.mobile-toggle:hover { background: var(--blue-d); }

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 35;
  animation: fadeIn 0.25s var(--ease-out);
}
.sidebar-overlay.show { display: block; }

/* 13. Mobile
   ------------------------------------------------------------------------ */
@media (max-width: 900px) {
  .sidebar {
    transform: translateX(-100%);
    width: 280px;
    box-shadow: var(--shadow-xl);
  }
  .sidebar.open { transform: translateX(0); }
  .main { margin-left: 0; }
  .content { padding: 20px 18px 60px; }
  .topbar { padding: 10px 16px; }
  .admin-bar { padding: 8px 16px; font-size: 11px; }
  .mobile-toggle { display: inline-flex; }
  .search { width: 140px; }
  .search:focus { width: 160px; }
  .lesson-title { font-size: calc(24px * var(--font-scale)); }
  .field-row { grid-template-columns: 1fr; }
  .drawer { width: 100vw; }
  .edit-actions { opacity: 1; }
}

/* 14. Print
   ------------------------------------------------------------------------ */
@media print {
  .sidebar, .topbar, .admin-bar, .lesson-footer, .lesson-edit-bar,
  .drawer-bg, .drawer { display: none !important; }
  .main { margin-left: 0; }
  .content { padding: 0; max-width: none; }
  body { background: #fff; color: #000; }
}