/* ─── Reset & tokens ─────────────────────────────────────────── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --bg-dark:      #0f172a;
  --bg-panel:     #1e293b;
  --bg-hover:     #2d3f55;
  --border:       #2d3f55;
  --text:         #f1f5f9;
  --text-muted:   #94a3b8;
  --accent:       #3b82f6;
  --accent-hover: #2563eb;
  --danger:       #ef4444;
  --success:      #22c55e;
  --toolbar-w:    62px;
  --topbar-h:     52px;
}

html, body { height: 100%; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; color: var(--text); }

/* ─── Whiteboard layout ──────────────────────────────────────── */
#wb-app {
  display: grid;
  grid-template-rows: var(--topbar-h) 1fr;
  grid-template-columns: var(--toolbar-w) 1fr;
  height: 100vh;
  height: 100dvh; /* excludes browser chrome on mobile */
  overflow: hidden;
  background: var(--bg-dark);
}

/* ─── Top bar ────────────────────────────────────────────────── */
#topbar {
  grid-column: 1 / -1;
  grid-row: 1;
  background: var(--bg-panel);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 14px;
  gap: 10px;
  z-index: 10;
}

.brand { font-weight: 800; font-size: 1.1rem; color: var(--text); white-space: nowrap; }
.brand span { color: var(--accent); }

.spacer { flex: 1; }

.room-badge {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 5px 12px;
  font-size: 0.82rem;
  color: var(--text-muted);
}
.room-badge strong { font-size: 1rem; font-family: monospace; color: var(--text); letter-spacing: 2px; }

/* ─── Top bar buttons ────────────────────────────────────────── */
.tb-btn {
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg-dark);
  color: var(--text);
  font-size: 0.8rem;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.12s, border-color 0.12s;
  display: flex;
  align-items: center;
  gap: 5px;
}
.tb-btn:hover { background: var(--bg-hover); border-color: var(--accent); }
.tb-btn.accent { background: var(--accent); border-color: var(--accent); color: #fff; }
.tb-btn.accent:hover { background: var(--accent-hover); }

/* ─── Toolbar (sidebar) ──────────────────────────────────────── */
#toolbar {
  grid-column: 1;
  grid-row: 2;
  background: var(--bg-panel);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 8px 0;
  gap: 2px;
  overflow-y: auto;
  overflow-x: hidden;
  scrollbar-width: none;
  z-index: 5;
}
#toolbar::-webkit-scrollbar { display: none; }

.tb-sep { width: 36px; height: 1px; background: var(--border); margin: 4px 0; flex-shrink: 0; }

/* Tool buttons */
.tool-btn {
  width: 46px;
  height: 46px;
  border: 1px solid transparent;
  border-radius: 10px;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 19px;
  transition: background 0.12s, color 0.12s, border-color 0.12s;
  flex-shrink: 0;
  position: relative;
}
.tool-btn:hover { background: var(--bg-hover); color: var(--text); }
.tool-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.tool-btn[title]:hover::after {
  content: attr(title);
  position: absolute;
  left: calc(100% + 10px);
  top: 50%;
  transform: translateY(-50%);
  background: #1a1a2e;
  color: var(--text);
  padding: 4px 8px;
  border-radius: 6px;
  font-size: 0.75rem;
  white-space: nowrap;
  pointer-events: none;
  z-index: 100;
  border: 1px solid var(--border);
}

/* Color swatch */
#color-swatch-wrap {
  width: 46px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  flex-shrink: 0;
}
#color-picker {
  width: 36px;
  height: 36px;
  border: 2px solid var(--border);
  border-radius: 50%;
  cursor: pointer;
  padding: 0;
  background: none;
  overflow: hidden;
}
#color-picker::-webkit-color-swatch-wrapper { padding: 0; }
#color-picker::-webkit-color-swatch { border: none; border-radius: 50%; }

.preset-colors {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 3px;
  width: 46px;
}
.color-dot {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  border: 2px solid transparent;
  cursor: pointer;
  transition: border-color 0.12s, transform 0.12s;
}
.color-dot:hover { transform: scale(1.2); }
.color-dot.active { border-color: #fff; }

/* Stroke sizes */
#size-btns {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  flex-shrink: 0;
}
.size-btn {
  width: 36px;
  height: 28px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.7rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  transition: background 0.12s, color 0.12s;
}
.size-btn:hover { background: var(--bg-hover); color: var(--text); }
.size-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.size-dot { background: currentColor; border-radius: 50%; flex-shrink: 0; }

/* ─── Canvas container ───────────────────────────────────────── */
#canvas-wrap {
  grid-column: 2;
  grid-row: 2;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  background: #d1d5db;
  position: relative;
}

#canvas-wrap canvas { display: block; }

/* ─── Modals ─────────────────────────────────────────────────── */
.modal-overlay {
  display: none;
  position: fixed; inset: 0;
  background: rgba(0,0,0,0.65);
  z-index: 200;
  align-items: center;
  justify-content: center;
  padding: 16px;
}
.modal-overlay.open { display: flex; }

.modal-box {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px 28px 24px;
  width: 100%;
  max-width: 420px;
  max-height: 90vh;
  overflow-y: auto;
}
.modal-box h2 { font-size: 1.15rem; margin-bottom: 6px; }
.modal-box p { font-size: 0.875rem; color: var(--text-muted); margin-bottom: 16px; line-height: 1.5; }

.code-display {
  font-size: 2.4rem;
  font-family: monospace;
  font-weight: 800;
  letter-spacing: 8px;
  color: var(--accent);
  text-align: center;
  padding: 16px;
  background: var(--bg-dark);
  border-radius: 10px;
  margin-bottom: 16px;
  border: 1px solid var(--border);
}

.link-row {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}
.link-row input {
  flex: 1;
  padding: 9px 12px;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text-muted);
  font-size: 0.78rem;
  outline: none;
  min-width: 0;
}
.link-row button {
  padding: 9px 14px;
  background: var(--accent);
  border: none;
  border-radius: 8px;
  color: #fff;
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
}
.link-row button:hover { background: var(--accent-hover); }

.modal-actions { display: flex; gap: 8px; justify-content: flex-end; margin-top: 4px; }
.btn-ghost {
  padding: 8px 16px; border: 1px solid var(--border); border-radius: 8px;
  background: transparent; color: var(--text-muted); font-size: 0.875rem; cursor: pointer;
}
.btn-ghost:hover { background: var(--bg-hover); color: var(--text); }
.btn-ok {
  padding: 8px 16px; border: none; border-radius: 8px;
  background: var(--accent); color: #fff; font-size: 0.875rem; font-weight: 600; cursor: pointer;
}
.btn-ok:hover { background: var(--accent-hover); }

/* PDF page selector */
.page-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 0 0 18px;
  max-height: 360px;
  overflow-y: auto;
  padding: 2px;
}

.page-chip {
  width: 90px;
  border: 2px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  cursor: pointer;
  background: var(--bg-dark);
  transition: border-color 0.12s, box-shadow 0.12s;
  user-select: none;
  flex-shrink: 0;
}
.page-chip:hover { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(59,130,246,0.15); }
.page-chip.selected { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(59,130,246,0.3); }

.page-chip-thumb {
  width: 100%;
  background: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 60px;
}
.page-chip-thumb canvas { width: 100%; display: block; }

.page-chip-label {
  padding: 4px 6px;
  text-align: center;
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--text-muted);
  background: var(--bg-panel);
  transition: background 0.12s, color 0.12s;
}
.page-chip.selected .page-chip-label { background: var(--accent); color: #fff; }

/* Shimmer placeholder while thumbnail renders */
.thumb-loading {
  width: 86px;
  height: 110px;
  background: linear-gradient(90deg, var(--bg-panel) 25%, var(--bg-hover) 50%, var(--bg-panel) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.2s infinite;
}
@keyframes shimmer {
  0%   { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* Filename dialog */
.filename-row {
  display: flex;
  align-items: center;
  margin-bottom: 16px;
}
.filename-row input {
  flex: 1;
  padding: 10px 12px;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-right: none;
  border-radius: 8px 0 0 8px;
  color: var(--text);
  font-size: 0.95rem;
  outline: none;
  min-width: 0;
}
.filename-row input:focus { border-color: var(--accent); }
.filename-ext {
  padding: 10px 12px;
  background: var(--bg-hover);
  border: 1px solid var(--border);
  border-radius: 0 8px 8px 0;
  color: var(--text-muted);
  font-size: 0.875rem;
  font-family: monospace;
  white-space: nowrap;
  flex-shrink: 0;
}

/* Jump-to-page row */
.jump-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
}
.jump-row label { font-size: 0.82rem; color: var(--text-muted); white-space: nowrap; }
.jump-row input {
  width: 72px;
  padding: 7px 10px;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 0.875rem;
  outline: none;
}
.jump-row input:focus { border-color: var(--accent); }
.jump-row button {
  padding: 7px 12px;
  background: var(--bg-hover);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 0.82rem;
  cursor: pointer;
  transition: background 0.12s, border-color 0.12s;
}
.jump-row button:hover { background: var(--accent); border-color: var(--accent); color: #fff; }

/* ─── Toast notifications ────────────────────────────────────── */
#toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(80px);
  background: #1e293b;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 20px;
  border-radius: 24px;
  font-size: 0.875rem;
  pointer-events: none;
  z-index: 500;
  transition: transform 0.2s ease, opacity 0.2s;
  opacity: 0;
  white-space: nowrap;
}
#toast.show { transform: translateX(-50%) translateY(0); opacity: 1; }

/* ─── Zoom display ───────────────────────────────────────────── */
.zoom-pct {
  font-size: 0.78rem;
  color: var(--text-muted);
  min-width: 42px;
  text-align: right;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

/* ─── Connection status ──────────────────────────────────────── */
#conn-status {
  width: 8px; height: 8px; border-radius: 50%;
  background: #94a3b8; flex-shrink: 0;
  transition: background 0.3s;
}
#conn-status.connected { background: var(--success); }
#conn-status.disconnected { background: var(--danger); }

/* ─── Viewer mode (student join) ────────────────────────────── */

/* Hide all host-only UI */
.viewer-mode #toolbar,
.viewer-mode #btn-undo,
.viewer-mode #btn-export-png,
.viewer-mode #btn-export-pdf,
.viewer-mode #btn-reset-view,
.viewer-mode #btn-share,
.viewer-mode .zoom-pct { display: none !important; }

/* Canvas fills full grid width (no toolbar column) */
.viewer-mode #canvas-wrap { grid-column: 1 / -1; }

/* Leave room at bottom for the viewer send bar */
.viewer-mode #canvas-wrap { padding-bottom: 84px; }

/* ── Viewer send bar ── */
#viewer-bar {
  display: none;
  position: fixed;
  bottom: 0; left: 0; right: 0;
  background: var(--bg-panel);
  border-top: 2px solid var(--border);
  padding: 12px 20px;
  padding-bottom: max(12px, env(safe-area-inset-bottom, 0px));
  gap: 14px;
  justify-content: center;
  z-index: 100;
}
.viewer-mode #viewer-bar { display: flex; }

.vsend-btn {
  flex: 1;
  max-width: 220px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 15px 18px;
  border: none;
  border-radius: 14px;
  font-size: 1.05rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.1s, filter 0.1s;
  -webkit-tap-highlight-color: transparent;
}
.vsend-btn:active { transform: scale(0.95); filter: brightness(0.88); }
.vsend-btn.cam { background: var(--accent); color: #fff; }
.vsend-btn.gal { background: var(--bg-hover); color: var(--text); border: 1px solid var(--border); }
.vsend-btn svg { flex-shrink: 0; }

/* ─── Mobile (≤ 640px) ───────────────────────────────────────── */
@media (max-width: 640px) {
  :root { --toolbar-w: 0px; --topbar-h: 48px; }

  #wb-app {
    grid-template-rows: var(--topbar-h) 1fr 60px;
    grid-template-columns: 1fr;
    height: 100dvh;
  }

  /* Viewer on mobile: no bottom toolbar row needed */
  #wb-app.viewer-mode {
    grid-template-rows: var(--topbar-h) 1fr;
  }

  #topbar { grid-column: 1; padding: 0 10px; gap: 8px; }
  .brand { font-size: 1rem; }
  .room-badge strong { font-size: 0.9rem; letter-spacing: 1px; }
  .tb-btn span.label { display: none; }

  #toolbar {
    grid-column: 1;
    grid-row: 3;
    grid-template-columns: repeat(auto-fill, 46px);
    flex-direction: row;
    border-right: none;
    border-top: 1px solid var(--border);
    width: 100%;
    overflow-x: auto;
    overflow-y: hidden;
    padding: 7px 8px;
    gap: 4px;
    align-items: center;
  }
  .tb-sep { width: 1px; height: 30px; margin: 0 4px; }
  #color-swatch-wrap { flex-direction: row; width: auto; }
  .preset-colors { flex-wrap: nowrap; width: auto; }
  #size-btns { flex-direction: row; }
  .tool-btn[title]:hover::after { display: none; }

  #canvas-wrap { grid-column: 1; grid-row: 2; }
}