To add an obstacle, click to a first end-point (blue square)
then click to the second end-point.
The user interface will silently
refuse to add vertical obstacles or
obstacles that cross existing ones.
To remove an obstacle, click to a first end-point (blue square) then click to the second end-point.
After giving the starting point and the ending point (positions) the system
gives a path avoiding
the obstacles. The path is smooth or piecewise
straight depending on the status of the
"Show Straight" check-box.
To see the cells used by the algorithm, tick the Show Cell check-box.