/* The problem tree and the lesson tree: a canvas you can drag and zoom, with
   panels for progress, zoom and the legend. */

/* a faint dot grid, so moving the canvas can be seen */
#tree-wrap {
  position: fixed; inset: 62px 0 0 0; overflow: hidden; cursor: grab;
  background-color: var(--bg);
  background-image: radial-gradient(color-mix(in srgb, var(--text3) 38%, transparent) 1px, transparent 1.2px); background-size: 24px 24px;
}
#tree-wrap.dragging { cursor: grabbing; }
#tree-svg { width: 100%; height: 100%; display: block; user-select: none; }

.tree-panel {
  background: color-mix(in srgb, var(--bg2) 94%, transparent);
  border: 1px solid var(--border2); border-radius: var(--radius-sm);
  box-shadow: var(--shadow); backdrop-filter: blur(8px);
}
#top-left { position: absolute; top: 76px; left: 16px; display: flex; flex-direction: column; gap: 8px; z-index: 5; }
#backToLevelsBtn { align-items: center; gap: 6px; }
#progress-badge { padding: 7px 12px; font-size: 0.9rem; color: var(--text2); }
#progress-badge strong { color: var(--text); font-variant-numeric: tabular-nums; }
#startBtn { display: none; } /* shown by JS when an open problem exists */

#controls { position: absolute; top: 76px; right: 16px; display: flex; flex-direction: column; gap: 6px; z-index: 5; }
.ctrl-btn {
  width: 38px; height: 38px; border-radius: var(--radius-sm);
  border: 1px solid var(--border2); background: var(--bg2); color: var(--text);
  font-size: 1.1rem; cursor: pointer; display: flex; align-items: center; justify-content: center;
}
.ctrl-btn:hover { background: var(--bg3); }

    /* legend, bottom */
#hud {
  position: absolute; bottom: 16px; left: 50%; transform: translateX(-50%);
  display: flex; gap: 14px; align-items: center; padding: 8px 16px; font-size: 0.84rem; color: var(--text2);
  white-space: nowrap; z-index: 5;
}
.hud-item { display: flex; align-items: center; gap: 6px; }
.hud-dot { width: 11px; height: 11px; border-radius: 0; flex-shrink: 0; }
.hud-sep { width: 1px; height: 16px; background: var(--border2); }
.hud-ramp { display: inline-flex; gap: 2px; }
.hud-ramp i { width: 10px; height: 10px; display: block; }

#tooltip {
  position: absolute; padding: 10px 13px; pointer-events: none; font-size: 0.88rem; color: var(--text);
  max-width: 250px; opacity: 0; transition: opacity 0.15s; z-index: 10;
  background: var(--bg2); border: 1px solid var(--border2); border-radius: var(--radius-sm); box-shadow: var(--shadow);
}
#tooltip.show { opacity: 1; }
.tip-title { font-weight: 700; margin-bottom: 4px; font-size: 0.95rem; }
.tip-meta { color: var(--text3); font-size: 0.82rem; }
.tip-status { margin-top: 5px; font-size: 0.84rem; font-weight: 600; }
.tip-hint { margin-top: 6px; font-size: 0.78rem; color: var(--text3); border-top: 1px solid var(--border); padding-top: 5px; }

#viewing-banner {
  display: none; position: absolute; top: 76px; left: 50%; transform: translateX(-50%); z-index: 6;
  background: var(--bg2); border: 1px solid var(--border2); border-left: 3px solid var(--gold);
  border-radius: var(--radius-sm); padding: 6px 14px; font-size: 0.88rem; font-weight: 600; color: var(--text); white-space: nowrap;
}
#viewing-banner a { color: var(--link); margin-left: 8px; font-weight: 500; }

@keyframes ringPulse { 0%,100% { opacity: 0.25 } 50% { opacity: 0.85 } }
.pulse-ring { animation: ringPulse 2s ease-in-out infinite; }