/* ═══════════════════════════════════════════════════
   CET-4/6 Learning App — Layout & Components
   ═══════════════════════════════════════════════════ */

/* ─── App Header ─── */
.app-header {
  background: var(--bg-header);
  color: var(--text-on-primary);
  height: var(--header-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--side-padding);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
}
.app-header .logo {
  font-size: 1.1rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 8px;
  letter-spacing: 0.3px;
}
.app-header .logo .icon { font-size: 1.4rem; }
.header-actions { display: flex; gap: 8px; align-items: center; }

/* ─── Theme Toggle ─── */
.theme-toggle {
  background: rgba(255,255,255,0.12);
  border: 1px solid rgba(255,255,255,0.2);
  color: var(--text-on-primary);
  width: 38px; height: 38px;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--ease);
  flex-shrink: 0;
}
.theme-toggle:hover {
  background: rgba(255,255,255,0.25);
  transform: rotate(15deg);
}

/* ─── Tab Navigation ─── */
.tab-nav {
  display: flex;
  background: var(--bg-nav);
  border-bottom: 2px solid var(--border);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  position: sticky;
  top: var(--header-h);
  z-index: 99;
  scrollbar-width: none;
}
.tab-nav::-webkit-scrollbar { display: none; }

.tab-nav button {
  flex: 1 0 auto;
  min-width: 80px;
  padding: 14px 18px;
  border: none;
  background: transparent;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  cursor: pointer;
  border-bottom: 3px solid transparent;
  white-space: nowrap;
  font-family: var(--font-sans);
  transition: all var(--ease);
  display: flex;
  align-items: center;
  gap: 6px;
  justify-content: center;
}
.tab-nav button:hover { color: var(--text-primary); background: var(--bg-card-hover); }
.tab-nav button.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
  font-weight: 600;
}
.tab-nav button .tab-icon { font-size: 1.1rem; }

/* ─── Tab Panels ─── */
.tab-panel {
  display: none;
  padding: 24px var(--side-padding);
  max-width: var(--content-max-w);
  margin: 0 auto;
  animation: fadeSlideIn 0.3s ease;
}
.tab-panel.active { display: block; }

@keyframes fadeSlideIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ─── Cards ─── */
.card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 16px;
  border: 1px solid var(--border-light);
  transition: box-shadow var(--ease), transform var(--ease);
}
.card:hover { box-shadow: var(--shadow); }
.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
  flex-wrap: wrap;
  gap: 8px;
}
.card-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
}

/* ─── Buttons ─── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 22px;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  border: 1.5px solid transparent;
  font-family: var(--font-sans);
  transition: all var(--ease);
  white-space: nowrap;
  user-select: none;
  line-height: 1.4;
}
.btn:active { transform: scale(0.97); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; pointer-events: none; }

.btn-primary {
  background: var(--accent);
  color: #FFF;
  border-color: var(--accent);
}
.btn-primary:hover { filter: brightness(1.12); box-shadow: var(--shadow-sm); }

.btn-secondary {
  background: transparent;
  color: var(--text-primary);
  border-color: var(--border);
}
.btn-secondary:hover { background: var(--bg-card-hover); border-color: var(--text-muted); }

.btn-success { background: var(--success); color: #FFF; }
.btn-success:hover { filter: brightness(1.12); }

.btn-danger { background: var(--danger); color: #FFF; }
.btn-danger:hover { filter: brightness(1.12); }

.btn-ghost {
  background: transparent;
  color: var(--accent);
  border-color: transparent;
}
.btn-ghost:hover { background: var(--bg-card-hover); }

.btn-lg { padding: 14px 32px; font-size: 1rem; border-radius: var(--radius); }
.btn-sm { padding: 6px 14px; font-size: 0.8rem; border-radius: var(--radius-xs); }
.btn-icon {
  width: 38px; height: 38px; padding: 0;
  border-radius: 50%;
}

/* ─── Form Elements ─── */
.form-group { margin-bottom: 16px; }
.form-label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

input[type="text"],
input[type="search"],
textarea,
select {
  width: 100%;
  padding: 10px 14px;
  font-size: 0.9rem;
  font-family: var(--font-sans);
  color: var(--text-primary);
  background: var(--bg-input);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  transition: border-color var(--ease), box-shadow var(--ease);
  line-height: 1.5;
}
input:focus, textarea:focus, select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(74, 144, 217, 0.15);
}
textarea { resize: vertical; min-height: 120px; }

/* ─── Radio / Option Buttons ─── */
.option-group { display: flex; flex-direction: column; gap: 10px; }
.option-btn {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 14px 16px;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all var(--ease);
  text-align: left;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  color: var(--text-primary);
  line-height: 1.5;
}
.option-btn:hover { border-color: var(--accent-light); background: var(--bg-card-hover); }
.option-btn.selected {
  border-color: var(--accent);
  background: rgba(74, 144, 217, 0.06);
  box-shadow: 0 0 0 1px var(--accent);
}
.option-btn.correct {
  border-color: var(--success);
  background: var(--success-light);
}
.option-btn.wrong {
  border-color: var(--danger);
  background: var(--danger-light);
}
.option-key {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px; height: 28px;
  border-radius: 50%;
  background: var(--bg-body);
  font-weight: 700;
  font-size: 0.8rem;
  color: var(--text-secondary);
  flex-shrink: 0;
  border: 1.5px solid var(--border);
}
.option-btn.selected .option-key {
  background: var(--accent);
  color: #FFF;
  border-color: var(--accent);
}
.option-btn.correct .option-key {
  background: var(--success);
  color: #FFF;
  border-color: var(--success);
}
.option-btn.wrong .option-key {
  background: var(--danger);
  color: #FFF;
  border-color: var(--danger);
}

/* ─── Progress Bar ─── */
.progress-bar {
  width: 100%;
  height: 8px;
  background: var(--border);
  border-radius: 4px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  border-radius: 4px;
  background: var(--accent);
  transition: width 0.5s ease;
}
.progress-fill.success { background: var(--success); }
.progress-fill.warning { background: var(--warning); }
.progress-fill.danger { background: var(--danger); }

/* ─── Badge / Tag ─── */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: 99px;
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--bg-body);
  color: var(--text-secondary);
  border: 1px solid var(--border);
}
.badge-accent { background: rgba(74, 144, 217, 0.1); color: var(--accent); border-color: transparent; }
.badge-success { background: var(--success-light); color: var(--success); border-color: transparent; }
.badge-danger { background: var(--danger-light); color: var(--danger); border-color: transparent; }
.badge-warning { background: var(--warning-light); color: var(--warning); border-color: transparent; }

/* ─── Dividers ─── */
hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 20px 0;
}

/* ─── Empty State ─── */
.empty-state {
  text-align: center;
  padding: 48px 24px;
  color: var(--text-muted);
}
.empty-state .icon { font-size: 3rem; margin-bottom: 12px; }
.empty-state p { font-size: 0.95rem; }

/* ─── Spinner ─── */
.spinner {
  width: 32px; height: 32px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  margin: 20px auto;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ─── Overlay / Modal ─── */
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  animation: fadeIn 0.2s ease;
}
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

.modal {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: 32px;
  max-width: 500px;
  width: 90%;
  box-shadow: var(--shadow-xl);
  animation: scaleIn 0.25s ease;
}
@keyframes scaleIn { from { transform: scale(0.95); opacity: 0; } to { transform: scale(1); opacity: 1; } }
.modal h3 { margin-bottom: 12px; }
.modal p { color: var(--text-secondary); margin-bottom: 20px; font-size: 0.9rem; }
.modal-actions { display: flex; gap: 10px; justify-content: flex-end; }

/* ─── Grid Layout ─── */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }

/* ─── Flex Utilities ─── */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.justify-center { justify-content: center; }
.gap-sm { gap: 8px; }
.gap { gap: 16px; }
.gap-lg { gap: 24px; }
.flex-1 { flex: 1; }
.flex-wrap { flex-wrap: wrap; }

/* ─── Text Utilities ─── */
.text-sm { font-size: 0.85rem; }
.text-xs { font-size: 0.75rem; }
.text-muted { color: var(--text-muted); }
.text-secondary { color: var(--text-secondary); }
.text-accent { color: var(--accent); }
.text-success { color: var(--success); }
.text-danger { color: var(--danger); }
.text-center { text-align: center; }
.font-bold { font-weight: 700; }
.font-mono { font-family: var(--font-mono); }

/* ─── Section Header ─── */
.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 10px;
}
.section-header h2 { margin: 0; }

/* ─── Footer ─── */
.app-footer {
  text-align: center;
  padding: 24px;
  color: var(--text-muted);
  font-size: 0.8rem;
  border-top: 1px solid var(--border);
  margin-top: 40px;
}

/* ─── Responsive ─── */
@media (max-width: 768px) {
  :root {
    --side-padding: 14px;
    --header-h: 50px;
    --nav-h: 44px;
  }

  .tab-nav button {
    font-size: 0.78rem;
    padding: 12px 14px;
    min-width: 65px;
  }
  .tab-panel { padding: 16px var(--side-padding); }

  .card { padding: 16px; border-radius: var(--radius-sm); }

  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }

  .app-header .logo { font-size: 0.95rem; }

  .btn { padding: 10px 18px; font-size: 0.85rem; }

  .modal { padding: 24px; width: 95%; }

  h1 { font-size: 1.4rem; }
  h2 { font-size: 1.2rem; }
}