Pick a sprite and add it to this project with the name "Target". It should not have a script, but if you wish, move it to (0, 0). Then click the green flag. Horizontal and vertical lines will converge on the Target from each of the boundaries. When they touch Target, each will disappear setting the corresponding variables marking the Target locations. Then the program will calculate the Target dimensions. Finally, it will display the x- and y-axes in black and draw diagonal lines to intersect at the center of Target.
I noticed that rotating an arbitrary sprite did not always turn it on its apparent center because the center of the sprit did not correspond to the center of the costume area. So this program determines the difference between the two.
