As the mouse pointer is moved, a rectangle of constant area is drawn (in yellow), aligned with the line from the origin to the mouse pointer. Notice that tracing the edge of a red circle produces movement in a corner of the rectangle which traces out a green circle. Notice that, conversely, tracing the edge of a green circle produces a the edge of a red circle.
The blue circles are produced by tracing out the horizontal white lines.Use cursor keys to move the view, + and - to zoom in and out. Press space to toggle animation.
Inspired by the constant area method from https://youtu.be/hSsRcpIsunk?t=167