@import url('https://fonts.googleapis.com/css2?family=Inter:wght@200;300;400;500;600;700&display=swap');

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

:root {
  --primary: #93C5FD;
  --secondary: #3B82F6;
  --tertiary: #B29BFF;
  --bg-from: #0a2342;
  --bg-via: #163e6e;
  --bg-to: #12385c;
  --glass-bg: rgba(255,255,255,0.08);
  --glass-bg-hover: rgba(255,255,255,0.13);
  --glass-border: rgba(255,255,255,0.18);
  --glass-border-strong: rgba(255,255,255,0.35);
  --text: #ffffff;
  --text-muted: rgba(255,255,255,0.6);
  --text-faint: rgba(255,255,255,0.35);
  --radius-sm: 4px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-2xl: 24px;
  --radius-full: 9999px;
  --blur: blur(12px);
  --blur-sm: blur(4px);
  --shadow: 0 4px 24px rgba(0,0,0,0.18);
  --shadow-sm: 0 2px 10px rgba(255,255,255,0.04);
  --transition: 300ms ease;
  --transition-fast: 150ms ease;
}

html, body {
  font-family: 'Inter', system-ui, sans-serif;
  background: linear-gradient(to bottom, var(--bg-from), var(--bg-via), var(--bg-to));
  min-height: 100vh;
  color: var(--text);
  font-size: 14px;
  line-height: 22.4px;
  font-weight: 200;
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.15); border-radius: 99px; }

/* ── Glass card ── */
.glass {
  background: var(--glass-bg);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border: 0.8px solid var(--glass-border);
  border-radius: var(--radius-lg);
}
.glass-strong {
  background: rgba(255,255,255,0.12);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border: 1.6px solid var(--glass-border-strong);
  border-radius: var(--radius-lg);
}
.glass-shell {
  padding: 6px;
  border-radius: var(--radius-2xl);
  background: linear-gradient(135deg, rgba(255,255,255,0.15), rgba(255,255,255,0.04));
  box-shadow: var(--shadow);
}
.glass-shell .glass-inner {
  border-radius: 20px;
  background: rgba(10,35,66,0.85);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border: 0.8px solid var(--glass-border);
  overflow: hidden;
}

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: var(--radius-full);
  font-family: 'Inter', sans-serif;
  font-size: 14px;
  font-weight: 400;
  cursor: pointer;
  border: none;
  transition: all var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
}
.btn-primary {
  background: var(--primary);
  color: #0a2342;
  font-weight: 500;
  box-shadow: 0 0 20px rgba(147,197,253,0.25);
}
.btn-primary:hover { background: #bfdbfe; box-shadow: 0 0 28px rgba(147,197,253,0.4); transform: translateY(-1px); }
.btn-secondary {
  background: rgba(255,255,255,0.1);
  color: var(--text);
  border: 0.8px solid var(--glass-border-strong);
}
.btn-secondary:hover { background: rgba(255,255,255,0.18); transform: translateY(-1px); }
.btn-ghost {
  background: transparent;
  color: var(--text-muted);
  padding: 8px 12px;
}
.btn-ghost:hover { color: var(--text); background: rgba(255,255,255,0.08); }
.btn-danger {
  background: rgba(239,68,68,0.2);
  color: #fca5a5;
  border: 0.8px solid rgba(239,68,68,0.3);
}
.btn-danger:hover { background: rgba(239,68,68,0.35); }
.btn-sm { padding: 6px 14px; font-size: 12px; }
.btn-icon { padding: 8px; border-radius: var(--radius-md); }
.btn:disabled { opacity: 0.4; cursor: not-allowed; transform: none !important; }

/* ── Inputs ── */
.input {
  width: 100%;
  padding: 12px 16px;
  background: rgba(255,255,255,0.07);
  border: 0.8px solid var(--glass-border);
  border-radius: var(--radius-md);
  color: var(--text);
  font-family: 'Inter', sans-serif;
  font-size: 14px;
  font-weight: 300;
  outline: none;
  transition: border-color var(--transition-fast), background var(--transition-fast);
}
.input::placeholder { color: var(--text-faint); }
.input:focus { border-color: var(--primary); background: rgba(255,255,255,0.1); }
.input-label {
  display: block;
  font-size: 12px;
  font-weight: 400;
  color: var(--text-muted);
  margin-bottom: 6px;
  letter-spacing: 0.03em;
}
select.input { cursor: pointer; }
select.input option { background: #1a4b82; color: white; }
textarea.input { resize: vertical; min-height: 120px; }

/* ── Typography ── */
h1 { font-size: 36px; font-weight: 500; line-height: 40px; letter-spacing: -0.025em; }
h2 { font-size: 24px; font-weight: 500; line-height: 32px; letter-spacing: -0.015em; }
h3 { font-size: 18px; font-weight: 500; line-height: 26px; }
h4 { font-size: 15px; font-weight: 500; }
.text-muted { color: var(--text-muted); }
.text-faint { color: var(--text-faint); }
.text-accent { color: var(--primary); }
.text-sm { font-size: 12px; line-height: 18px; }
.text-xs { font-size: 11px; }

/* ── Layout ── */
.page-wrap { min-height: 100vh; padding: 32px; }
.container { max-width: 1200px; margin: 0 auto; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.grid-3 { display: grid; grid-template-columns: repeat(3,1fr); gap: 12px; }
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: 8px; }
.gap-3 { gap: 12px; }
.gap-4 { gap: 16px; }
.mt-1 { margin-top: 4px; }
.mt-2 { margin-top: 8px; }
.mt-3 { margin-top: 12px; }
.mt-4 { margin-top: 16px; }
.mt-6 { margin-top: 24px; }
.mt-8 { margin-top: 32px; }
.mb-2 { margin-bottom: 8px; }
.mb-4 { margin-bottom: 16px; }
.mb-6 { margin-bottom: 24px; }
.p-4 { padding: 16px; }
.p-6 { padding: 24px; }
.p-8 { padding: 32px; }

/* ── Badge / Tag ── */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: var(--radius-full);
  font-size: 11px;
  font-weight: 400;
  letter-spacing: 0.02em;
  background: rgba(147,197,253,0.15);
  color: var(--primary);
  border: 0.8px solid rgba(147,197,253,0.25);
}
.badge-green { background: rgba(74,222,128,0.12); color: #86efac; border-color: rgba(74,222,128,0.2); }
.badge-purple { background: rgba(178,155,255,0.15); color: var(--tertiary); border-color: rgba(178,155,255,0.25); }
.badge-orange { background: rgba(251,146,60,0.15); color: #fdba74; border-color: rgba(251,146,60,0.25); }

/* ── Progress bar ── */
.progress-wrap { background: rgba(255,255,255,0.1); border-radius: var(--radius-full); height: 6px; overflow: hidden; }
.progress-bar { height: 100%; border-radius: var(--radius-full); background: linear-gradient(90deg, var(--secondary), var(--primary)); transition: width 600ms ease; }

/* ── Topbar ── */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 24px;
  background: rgba(10,35,66,0.7);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border-bottom: 0.8px solid var(--glass-border);
  position: sticky; top: 0; z-index: 100;
}
.topbar-logo { font-size: 15px; font-weight: 500; color: var(--primary); letter-spacing: -0.01em; display: flex; align-items: center; gap: 8px; }

/* ── Sidebar ── */
.layout-split { display: grid; grid-template-columns: 280px 1fr; min-height: calc(100vh - 57px); }
.sidebar {
  background: rgba(10,35,66,0.6);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border-right: 0.8px solid var(--glass-border);
  padding: 20px 12px;
  overflow-y: auto;
}
.sidebar-item {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 12px;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  border: 0.8px solid transparent;
  margin-bottom: 2px;
  font-size: 13px; font-weight: 300;
  color: var(--text-muted);
}
.sidebar-item:hover { background: var(--glass-bg); color: var(--text); border-color: var(--glass-border); }
.sidebar-item.active { background: rgba(147,197,253,0.12); color: var(--primary); border-color: rgba(147,197,253,0.2); }
.sidebar-item.done .si-icon { color: #86efac; }

/* ── Course card ── */
.course-card {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 0.8px solid var(--glass-border);
  background: var(--glass-bg);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  transition: all var(--transition);
  cursor: pointer;
  text-decoration: none;
  color: var(--text);
  display: block;
}
.course-card:hover { transform: translateY(-4px); border-color: rgba(147,197,253,0.35); box-shadow: 0 12px 40px rgba(0,0,0,0.25); background: var(--glass-bg-hover); }
.course-card-img { width: 100%; height: 180px; object-fit: cover; display: block; }
.course-card-img-placeholder { width: 100%; height: 180px; background: linear-gradient(135deg, rgba(147,197,253,0.2), rgba(59,130,246,0.15)); display: flex; align-items: center; justify-content: center; font-size: 48px; }
.course-card-body { padding: 16px; }

/* ── Lesson content area ── */
.lesson-content { padding: 32px 40px; max-width: 800px; }
.lesson-content h2 { font-size: 22px; font-weight: 500; margin: 28px 0 12px; color: var(--primary); }
.lesson-content h3 { font-size: 16px; font-weight: 500; margin: 20px 0 8px; }
.lesson-content p { margin-bottom: 14px; line-height: 1.7; font-weight: 300; color: rgba(255,255,255,0.88); }
.lesson-content ul, .lesson-content ol { margin: 0 0 14px 20px; }
.lesson-content li { margin-bottom: 6px; line-height: 1.6; color: rgba(255,255,255,0.85); }
.lesson-content strong { font-weight: 500; color: white; }
.lesson-content em { color: var(--primary); font-style: normal; }

/* ── Video embed ── */
.video-wrap { border-radius: var(--radius-lg); overflow: hidden; background: #000; margin: 24px 0; box-shadow: var(--shadow); }
.video-wrap iframe { display: block; width: 100%; aspect-ratio: 16/9; border: none; }

/* ── Image gallery ── */
.gallery { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px,1fr)); gap: 8px; margin: 20px 0; }
.gallery img { width: 100%; border-radius: var(--radius-md); cursor: pointer; transition: transform var(--transition-fast); object-fit: cover; aspect-ratio: 16/9; border: 0.8px solid var(--glass-border); }
.gallery img:hover { transform: scale(1.02); }

/* ── Lightbox ── */
.lightbox { position: fixed; inset: 0; background: rgba(0,0,0,0.9); z-index: 1000; display: flex; align-items: center; justify-content: center; padding: 32px; opacity: 0; transition: opacity var(--transition); pointer-events: none; }
.lightbox.open { opacity: 1; pointer-events: all; }
.lightbox img { max-width: 90vw; max-height: 85vh; border-radius: var(--radius-lg); object-fit: contain; }
.lightbox-close { position: absolute; top: 20px; right: 24px; background: rgba(255,255,255,0.1); border: none; color: white; font-size: 24px; cursor: pointer; width: 40px; height: 40px; border-radius: var(--radius-full); display: flex; align-items: center; justify-content: center; }

/* ── Quiz ── */
.quiz-option {
  padding: 14px 18px;
  border-radius: var(--radius-md);
  border: 0.8px solid var(--glass-border);
  background: var(--glass-bg);
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex; align-items: center; gap: 12px;
  font-weight: 300;
}
.quiz-option:hover { background: var(--glass-bg-hover); border-color: rgba(147,197,253,0.3); }
.quiz-option.selected { background: rgba(147,197,253,0.12); border-color: var(--primary); color: var(--primary); }
.quiz-option.correct { background: rgba(74,222,128,0.12); border-color: #86efac; color: #86efac; }
.quiz-option.wrong { background: rgba(248,113,113,0.12); border-color: #fca5a5; color: #fca5a5; }
.quiz-dot { width: 18px; height: 18px; border-radius: var(--radius-full); border: 1.6px solid currentColor; flex-shrink: 0; display: flex; align-items: center; justify-content: center; }
.quiz-dot.filled { background: currentColor; }

/* ── Tabs ── */
.tabs { display: flex; gap: 2px; border-bottom: 0.8px solid var(--glass-border); margin-bottom: 24px; }
.tab-btn {
  padding: 10px 20px; border: none; background: transparent; color: var(--text-muted);
  font-family: 'Inter', sans-serif; font-size: 13px; font-weight: 400; cursor: pointer;
  border-bottom: 2px solid transparent; transition: all var(--transition-fast); margin-bottom: -1px;
}
.tab-btn:hover { color: var(--text); }
.tab-btn.active { color: var(--primary); border-bottom-color: var(--primary); }
.tab-pane { display: none; }
.tab-pane.active { display: block; }

/* ── Table ── */
.table { width: 100%; border-collapse: collapse; }
.table th { text-align: left; padding: 10px 14px; font-size: 11px; font-weight: 500; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; border-bottom: 0.8px solid var(--glass-border); }
.table td { padding: 12px 14px; font-size: 13px; font-weight: 300; border-bottom: 0.8px solid rgba(255,255,255,0.05); vertical-align: middle; }
.table tr:hover td { background: rgba(255,255,255,0.03); }

/* ── Modal ── */
.modal-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.6); z-index: 200; display: flex; align-items: center; justify-content: center; padding: 32px; opacity: 0; transition: opacity var(--transition); pointer-events: none; backdrop-filter: blur(4px); }
.modal-overlay.open { opacity: 1; pointer-events: all; }
.modal { background: #0e2d55; border: 1.6px solid var(--glass-border-strong); border-radius: var(--radius-xl); padding: 28px; max-width: 560px; width: 100%; max-height: 85vh; overflow-y: auto; box-shadow: 0 20px 60px rgba(0,0,0,0.4); transform: translateY(16px); transition: transform var(--transition); }
.modal-overlay.open .modal { transform: translateY(0); }
.modal-header { display: flex; align-items: center; justify-content: space-between; margin-bottom: 20px; }
.modal-close { background: none; border: none; color: var(--text-muted); cursor: pointer; font-size: 20px; padding: 4px; border-radius: var(--radius-sm); transition: color var(--transition-fast); }
.modal-close:hover { color: var(--text); }

/* ── Toasts ── */
#toast-container { position: fixed; bottom: 24px; right: 24px; z-index: 999; display: flex; flex-direction: column; gap: 8px; }
.toast { padding: 12px 20px; border-radius: var(--radius-md); border: 0.8px solid var(--glass-border); backdrop-filter: var(--blur); -webkit-backdrop-filter: var(--blur); font-size: 13px; font-weight: 400; animation: toastIn 300ms ease; box-shadow: var(--shadow); }
.toast-success { background: rgba(74,222,128,0.15); color: #86efac; border-color: rgba(74,222,128,0.3); }
.toast-error { background: rgba(248,113,113,0.15); color: #fca5a5; border-color: rgba(248,113,113,0.3); }
.toast-info { background: rgba(147,197,253,0.15); color: var(--primary); border-color: rgba(147,197,253,0.3); }
@keyframes toastIn { from { opacity: 0; transform: translateX(20px); } to { opacity: 1; transform: none; } }

/* ── Dividers ── */
.divider { border: none; border-top: 0.8px solid var(--glass-border); margin: 20px 0; }

/* ── Stat card ── */
.stat-card { padding: 20px; text-align: center; }
.stat-number { font-size: 36px; font-weight: 500; letter-spacing: -0.025em; color: var(--primary); line-height: 40px; }
.stat-label { font-size: 12px; color: var(--text-muted); margin-top: 4px; }

/* ── Empty state ── */
.empty-state { text-align: center; padding: 48px 24px; color: var(--text-muted); }
.empty-state .icon { font-size: 40px; margin-bottom: 12px; opacity: 0.5; }

/* ── Animations ── */
@keyframes fadeIn { from { opacity: 0; transform: translateY(12px); } to { opacity: 1; transform: none; } }
.fade-in { animation: fadeIn 500ms ease forwards; }
.fade-in-delay-1 { animation-delay: 100ms; opacity: 0; }
.fade-in-delay-2 { animation-delay: 200ms; opacity: 0; }
.fade-in-delay-3 { animation-delay: 300ms; opacity: 0; }

/* ── Responsive ── */
@media (max-width: 900px) {
  .grid-3 { grid-template-columns: 1fr 1fr; }
  .layout-split { grid-template-columns: 1fr; }
  .sidebar { display: none; }
  .page-wrap { padding: 16px; }
  h1 { font-size: 26px; line-height: 32px; }
}
@media (max-width: 600px) {
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .lesson-content { padding: 20px 16px; }
}