Drag the point or the circles — tangents, touch-points, and the 0–4 common-tangent count update live
| Operation | Time |
|---|---|
| Distance d | O(1) |
| Tangent length √(d²−r²) | O(1) |
| Touch-points | O(1) |
| Classify pair (0–4) | O(1) |
| All common tangents | O(1) |
| Tangent graph (n discs) | O(n²) |