In Insert mode, click and drag to specify a new rectangle. In Delete mode click inside an existing rectangle to remove it from the quadtree. If you click in an area that is occupied by several rectangles, one of them will be chosen arbitrarily and deleted.
In Move mode, you can click and drag to specify a rectangle. The yellow rectangle corresponds to the rectangle that is being operated upon. The blue square is the minimum enclosing quadtree block containing the yellow rectangle. The green square corresponds to the expanded blue quadtree block, containing the yellow rectangle. The yellow rectangle is reinserted in to the loose quadtree as soon as the centroid of the yellow rectangle extends past the blue quadtree block.
In Motion Insensitivity mode, you can click and drag to specify a rectangle. The yellow rectangle corresponds to the rectangle that is being operated upon. The blue square is the minimum enclosing quadtree block containing the yellow rectangle. The green square corresponds to the expanded blue quadtree block, containing the yellow rectangle. The yellow rectangle is reinserted in to the loose quadtree as soon as it touches the green square. The difference between Motion Insensitivity and the Move operation is that in the case of the Motion Insensitivity the centroid of the yellow rectangle can lie outside the blue quadtree block.
In Show Quadtree mode, the yellow rectangle corresponds to the rectangle that is being operated upon. The blue square is the minimum enclosing quadtree block containing the yellow rectangle. The green square corresponds to the expanded blue quadtree block, containing the yellow rectangle.