:root {
  --primary: #06b6d4;
  --primary-hover: #0891b2;
  --primary-light: rgba(6, 182, 212, 0.12);
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --text: #0f172a;
  --text-muted: #64748b;
  --radius: 12px;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.08), 0 2px 4px -2px rgb(0 0 0 / 0.05);

  --gender-male: #0284c7;
  --gender-female: #ec4899;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0f19;
    --card-bg: #111827;
    --border: #1f2937;
    --text: #f9fafb;
    --text-muted: #9ca3af;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
    --primary-light: rgba(6, 182, 212, 0.18);
  }
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

body {
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.5;
  padding: 24px 16px;
}

.app-container {
  max-width: 1320px;
  margin: 0 auto;
}

/* Header */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 20px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 14px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: var(--radius);
  text-decoration: none;
  font-size: 0.88rem;
  font-weight: 500;
  transition: all 0.2s;
}

.btn-back:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.header-icon {
  width: 48px;
  height: 48px;
  background: var(--primary-light);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius);
}

.header-icon svg {
  width: 26px;
  height: 26px;
}

h1 {
  font-size: 1.65rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.subtitle {
  color: var(--text-muted);
  font-size: 0.88rem;
}

.header-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

/* Mode Switch Tabs */
.mode-tabs {
  display: flex;
  gap: 12px;
  margin-bottom: 20px;
}

.mode-tab {
  background: var(--card-bg);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 10px 20px;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: all 0.2s;
}

.mode-tab.active {
  background: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
  box-shadow: 0 4px 12px rgba(6, 182, 212, 0.3);
}

/* Layout */
.main-layout {
  display: grid;
  grid-template-columns: 340px 1fr;
  gap: 24px;
}

@media (max-width: 960px) {
  .main-layout {
    grid-template-columns: 1fr;
  }
}

/* Sidebar */
.sidebar-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
}

.sidebar-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.sidebar-header h2 {
  font-size: 1.15rem;
  font-weight: 700;
}

.badge-count {
  background: var(--primary-light);
  color: var(--primary);
  padding: 3px 8px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
}

.hint {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 12px;
}

#roster-input {
  width: 100%;
  height: 380px;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px;
  font-family: inherit;
  font-size: 0.88rem;
  line-height: 1.6;
  resize: vertical;
  margin-bottom: 12px;
  outline: none;
}

#roster-input:focus {
  border-color: var(--primary);
}

.roster-actions {
  display: flex;
  gap: 8px;
}

/* Common Buttons */
button {
  cursor: pointer;
  border: none;
  border-radius: 8px;
  font-size: 0.88rem;
  font-weight: 600;
  padding: 8px 16px;
  transition: all 0.2s ease;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
}

.btn-primary {
  background: linear-gradient(135deg, #06b6d4, #0284c7);
  color: #ffffff;
}

.btn-primary:hover {
  opacity: 0.92;
  box-shadow: 0 4px 12px rgba(6, 182, 212, 0.3);
}

.btn-secondary {
  background: var(--card-bg);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: rgba(148, 163, 184, 0.1);
  border-color: var(--text-muted);
}

/* Controls */
.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  margin-bottom: 20px;
}

.controls-row {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

.ctrl-group {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.88rem;
}

.ctrl-group label {
  font-weight: 600;
  color: var(--text-muted);
}

select, input[type="number"] {
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 12px;
  font-size: 0.88rem;
  outline: none;
}

select:focus, input:focus {
  border-color: var(--primary);
}

.checkbox-ctrl label {
  display: flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  color: var(--text);
}

/* Views */
.mode-view {
  display: none;
}

.mode-view.active {
  display: block;
}

/* Groups Output */
.groups-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 16px;
}

.group-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow);
}

.group-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 8px;
  margin-bottom: 10px;
  border-bottom: 1px solid var(--border);
}

.group-title {
  font-weight: 700;
  font-size: 1rem;
  color: var(--primary);
}

.group-members {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.member-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.88rem;
  padding: 4px 8px;
  background: rgba(148, 163, 184, 0.06);
  border-radius: 6px;
}

.gender-tag {
  font-size: 0.75rem;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 600;
}

.gender-male { background: rgba(2, 132, 199, 0.12); color: var(--gender-male); }
.gender-female { background: rgba(236, 72, 153, 0.12); color: var(--gender-female); }

/* Seating Output */
.chalkboard-podium {
  background: #1e293b;
  color: #f8fafc;
  border-radius: 8px;
  padding: 12px;
  text-align: center;
  font-weight: 700;
  letter-spacing: 0.05em;
  margin-bottom: 24px;
  border: 2px dashed #475569;
}

.seating-matrix {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.seating-row {
  display: flex;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
}

.seating-export-area {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}

.seating-export-header {
  text-align: center;
  margin-bottom: 20px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--border);
}

.seating-export-header h3 {
  font-size: 1.35rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--text);
  margin-bottom: 4px;
}

.seating-export-header p {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.desk-block {
  background: var(--card-bg);
  border: 2px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  min-width: 140px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.desk-header {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-align: center;
  font-weight: 600;
  border-bottom: 1px solid var(--border);
  padding-bottom: 4px;
}

.seat-slot {
  padding: 8px 10px;
  border-radius: 6px;
  background: var(--bg);
  border: 1px solid var(--border);
  font-size: 0.85rem;
  font-weight: 500;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  cursor: grab;
  user-select: none;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
}

.seat-slot:active {
  cursor: grabbing;
}

.seat-slot.dragging {
  opacity: 0.45;
  transform: scale(0.96);
  border: 2px dashed var(--primary);
  background: var(--primary-light);
}

.seat-slot.drag-over {
  border: 2px dashed #0284c7;
  background: rgba(2, 132, 199, 0.15);
  transform: scale(1.04);
  box-shadow: 0 4px 12px rgba(2, 132, 199, 0.25);
}

.seat-slot.empty {
  color: var(--text-muted);
  font-style: italic;
  opacity: 0.75;
  border-style: dashed;
}

.empty-state {
  text-align: center;
  padding: 40px 20px;
  color: var(--text-muted);
  background: var(--card-bg);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
}

.app-footer {
  text-align: center;
  padding: 24px 0;
  color: var(--text-muted);
  font-size: 0.82rem;
}

/* Toast Notification */
.toast-msg {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background: #0f172a;
  color: #f8fafc;
  padding: 12px 20px;
  border-radius: 8px;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
  font-size: 0.9rem;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 10px;
  z-index: 9999;
  animation: toastFadeIn 0.25s ease-out;
}

@keyframes toastFadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

@media print {
  body {
    background: #ffffff;
    color: #000000;
    padding: 0;
  }
  .app-header .header-actions, .btn-back, .mode-tabs, .sidebar-card, .control-box, .app-footer {
    display: none !important;
  }
  .main-layout {
    display: block !important;
  }
  .seating-export-area, .card, .group-card, .desk-block {
    box-shadow: none !important;
    border: 1px solid #ccc !important;
    color: #000 !important;
    background: #fff !important;
  }
  .seat-slot {
    background: #fff !important;
    border-color: #ddd !important;
    color: #000 !important;
  }
  .chalkboard-podium {
    background: #f1f5f9 !important;
    color: #000 !important;
    border-color: #94a3b8 !important;
  }
}