Calculate properties automatically
Click the display area to create a vertex.
Drag vertices around to rearrange them.
Click a vertex to select it and it will turn green.
Click another vertex to connect the two with an edge.
Click on a blank area to deselect the vertex.
Click another already connected vertex to remove the edge between them.
while connecting vertices to keep selecting the vertex you click on.
+click a vertex to delete it and any edges connected to it.