:root {
  --bg: #f0f4f8;
  --surface: #ffffff;
  --ink: #1a2332;
  --muted: #5a6a7e;
  --border: #d5dee8;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-soft: #dbeafe;
  --success: #16a34a;
  --success-bg: #dcfce7;
  --success-border: #86efac;
  --danger: #dc2626;
  --danger-bg: #fee2e2;
  --danger-border: #fca5a5;
  --empty-bg: #f1f5f9;
  --empty-border: #cbd5e1;
  --grid: #e2e8f0;
  --shadow: 0 1px 3px rgba(15, 23, 42, 0.08), 0 4px 16px rgba(15, 23, 42, 0.06);
  --radius: 12px;
  --desk-size: 88px;
  --grid-size: 96px;
  --font: "Segoe UI", system-ui, -apple-system, sans-serif;
}

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

html,
body {
  margin: 0;
  min-height: 100%;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
}

button,
input {
  font: inherit;
}

.app {
  max-width: 1400px;
  margin: 0 auto;
  padding: 16px 20px 32px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-height: 100vh;
}

/* Header */
.top-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.brand h1 {
  margin: 0;
  font-size: 1.45rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.subtitle {
  margin: 2px 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.mode-toggle {
  display: inline-flex;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 4px;
  box-shadow: var(--shadow);
}

.mode-btn {
  border: none;
  background: transparent;
  color: var(--muted);
  padding: 8px 18px;
  border-radius: 999px;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.15s, color 0.15s;
}

.mode-btn:hover {
  color: var(--ink);
}

.mode-btn.active {
  background: var(--primary);
  color: #fff;
}

/* Meta + toolbar */
.meta-bar,
.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: flex-end;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  box-shadow: var(--shadow);
}

.field {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 160px;
  flex: 1;
}

.field span {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.field input {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 10px;
  background: #fff;
  color: var(--ink);
}

.field input:focus {
  outline: 2px solid var(--primary-soft);
  border-color: var(--primary);
}

.toolbar {
  align-items: center;
  gap: 8px;
}

.toolbar .spacer {
  flex: 1;
  min-width: 8px;
}

.btn {
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--ink);
  border-radius: 8px;
  padding: 8px 14px;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.9rem;
  transition: background 0.12s, border-color 0.12s, transform 0.05s;
}

.btn:hover {
  background: #f8fafc;
}

.btn:active {
  transform: translateY(1px);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

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

.btn-success {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
}

.btn-success:hover {
  filter: brightness(0.95);
}

.btn-danger {
  background: #fff;
  border-color: var(--danger-border);
  color: var(--danger);
}

.btn-danger:hover {
  background: var(--danger-bg);
}

.btn-ghost {
  background: transparent;
}

.btn-sm {
  padding: 6px 10px;
  font-size: 0.85rem;
}

/* Workspace */
.workspace {
  display: grid;
  grid-template-columns: 1fr 260px;
  gap: 14px;
  flex: 1;
  min-height: 0;
}

@media (max-width: 900px) {
  .workspace {
    grid-template-columns: 1fr;
  }
}

.canvas-wrap {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-height: 520px;
}

.canvas-hint {
  font-size: 0.85rem;
  color: var(--muted);
  min-height: 1.2em;
}

.classroom {
  position: relative;
  flex: 1;
  min-height: 560px;
  border-radius: 10px;
  border: 1px dashed var(--border);
  background-color: #fafbfc;
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: var(--grid-size) var(--grid-size);
  overflow: auto;
  touch-action: none;
  user-select: none;
}

.classroom.attendance-mode {
  cursor: default;
}

.classroom.setup-mode {
  cursor: default;
}

/* Front of room label */
.classroom::before {
  content: "FRONT OF ROOM";
  position: absolute;
  top: 8px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: #94a3b8;
  pointer-events: none;
  z-index: 0;
}

/* Drop target preview while dragging */
.drop-preview {
  position: absolute;
  width: var(--desk-size);
  height: var(--desk-size);
  border-radius: 10px;
  border: 2px dashed transparent;
  pointer-events: none;
  z-index: 5;
  box-sizing: border-box;
}

.drop-preview.valid {
  background: rgba(34, 197, 94, 0.18);
  border-color: #22c55e;
}

.drop-preview.invalid {
  background: rgba(239, 68, 68, 0.15);
  border-color: #ef4444;
}

/* Desks */
.desk {
  position: absolute;
  width: var(--desk-size);
  height: var(--desk-size);
  border-radius: 10px;
  border: 2px solid var(--empty-border);
  background: var(--empty-bg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 6px;
  text-align: center;
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.06);
  cursor: grab;
  z-index: 1;
  transition: box-shadow 0.12s, border-color 0.12s, background 0.12s;
  touch-action: none;
  -webkit-user-drag: none;
  user-select: none;
}

.desk .desk-name,
.desk .desk-status-label {
  pointer-events: none;
}

.desk:hover {
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.12);
  z-index: 2;
}

.desk.dragging {
  cursor: grabbing;
  opacity: 0.95;
  z-index: 20;
  box-shadow: 0 12px 28px rgba(15, 23, 42, 0.22);
  transition: none;
  pointer-events: none; /* keep pointer events on document during drag */
}

.desk.dragging.drop-invalid {
  outline: 2px solid #ef4444;
  outline-offset: 2px;
}

.desk.selected {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.desk.status-here {
  background: var(--success-bg);
  border-color: var(--success-border);
}

.desk.status-absent {
  background: var(--danger-bg);
  border-color: var(--danger-border);
}

.desk.status-empty {
  background: var(--empty-bg);
  border-color: var(--empty-border);
}

.classroom.attendance-mode .desk {
  cursor: pointer;
}

.classroom.setup-mode .desk {
  cursor: grab;
}

.desk-name {
  font-size: 0.78rem;
  font-weight: 700;
  line-height: 1.2;
  word-break: break-word;
  max-width: 100%;
  color: var(--ink);
}

.desk-name.is-empty {
  font-weight: 600;
  color: var(--muted);
  font-style: italic;
}

.desk-status-label {
  margin-top: 4px;
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
}

.desk.status-here .desk-status-label {
  color: var(--success);
}

.desk.status-absent .desk-status-label {
  color: var(--danger);
}

.desk-edit-btn {
  position: absolute;
  top: 2px;
  right: 2px;
  width: 22px;
  height: 22px;
  border: none;
  border-radius: 6px;
  background: rgba(255, 255, 255, 0.85);
  color: var(--muted);
  font-size: 0.75rem;
  cursor: pointer;
  line-height: 1;
  padding: 0;
  display: none;
}

.classroom.setup-mode .desk:hover .desk-edit-btn,
.classroom.setup-mode .desk.selected .desk-edit-btn {
  display: block;
}

.desk-edit-btn:hover {
  background: var(--primary-soft);
  color: var(--primary);
}

/* Side panel */
.side-panel {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.panel-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  box-shadow: var(--shadow);
}

.panel-card h2 {
  margin: 0 0 10px;
  font-size: 0.95rem;
}

.stats {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-size: 0.9rem;
  color: var(--muted);
}

.stats strong {
  color: var(--ink);
}

.dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  margin-right: 4px;
  vertical-align: middle;
}

.dot.here {
  background: var(--success);
}

.dot.absent {
  background: var(--danger);
}

.dot.empty {
  background: #94a3b8;
}

.help-card {
  font-size: 0.85rem;
  color: var(--muted);
  line-height: 1.45;
}

.help-card ul {
  margin: 0;
  padding-left: 1.1rem;
}

.help-card li {
  margin-bottom: 6px;
}

.help-card kbd {
  display: inline-block;
  background: #f1f5f9;
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0 5px;
  font-size: 0.78rem;
  font-family: inherit;
  color: var(--ink);
}

/* Toast */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--ink);
  color: #fff;
  padding: 10px 18px;
  border-radius: 999px;
  font-size: 0.9rem;
  font-weight: 600;
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.25);
  z-index: 100;
  max-width: 90vw;
}

.toast[hidden] {
  display: none;
}

/* Dialog */
.dialog {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0;
  box-shadow: 0 20px 50px rgba(15, 23, 42, 0.2);
  width: min(360px, 92vw);
}

.dialog::backdrop {
  background: rgba(15, 23, 42, 0.35);
}

.dialog form {
  padding: 18px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.dialog h3 {
  margin: 0;
}

.dialog-hint {
  margin: 0;
  font-size: 0.85rem;
  color: var(--muted);
}

.dialog input {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 12px;
  width: 100%;
}

.dialog input:focus {
  outline: 2px solid var(--primary-soft);
  border-color: var(--primary);
}

.dialog-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
  margin-top: 4px;
}