[qrjbprpk] Drawing with orthogonal lines

Yet another simple drawing interface:

Any rectangle may be divided vertically or horizontally by a line, or quartered at an internal point.  Lines may extended, dividing a different rectangle (need not be adjacent).  Lines may be locked to remain a given distance apart (will matter when moving lines).  Distance measured perpendicularly, even if there is no perpendicular line that will intersect two segments.

Lines and quartering points may be moved independently, until they hit the edge of of the rectangle they are in (this becomes tricky with locked lines.)  Moving a line or quartering point can also scale the content on either side or around it.  (Locked lines inside keep same scaling.)

Rectangles may be flat shaded, or gradient shaded according to the Delauney triangulation of the their center points.  Or coloring edges (even separately coloring both sides of an edge).

Lines may be deleted so long as the remaining area is a rectangle. This makes it possible to draw a galaxy.

Inspired by quadtrees and k-d trees. (Also see the Voronoi interface.)

Piet Mondrian, of course.

We may extend the idea from rectangles to triangles and arbitrary different polygons, but the UI becomes much messier.