Initial location of the point (x,y)

after a movement, the point will move a proportional amount relative to the location of the point on the diagonal line connecting the y-axis point and the x-axis point.

ASSUME: the point is at the MIDPOINT of the diagonal.

If the initial movement is 2D then

after an initial movement

location of the point (x+d,y-d)

after a 2nd equal movement

location of the point (x+2d, y-2d)

after a 3rd equal movement

location of the point (x+3d, y-3d)

It is linear.

The path is a line.

[As stated, the "diagonal" is increasing in length with each movement.]

Hope that helps.