I asked some of my more able students to create the above shape in Turtle Art (from the Barry Newell shape sheet) using variables, so that by varying the input value they could create the same shape in different sizes, as shown below:
Well, this did set the cat amongst the pigeons even amongst my better students who had been happily in the groove making complex shapes from the BN sheet. One problem was that in their procedure they were using subtraction to alter side length and of course this will not work for variable size shapes.
Another issue is that despite doing algebra out of a textbook they didn't really grasp the box model of a variable, that you need for programming. Imagine a box which has a name, which doesn't vary, but you can put numbers (or other things) in the box which do vary.
So, I realised this was a nice challenge in real maths and understanding of the application of variables, measurement, ratio, proportion and fractions. I see this as an excellent example of constructionist maths in contrast to textbook maths.
Clue: When I measure the lengths of the "curly rectangle" (not sure what the correct name is) on a larger diagram in BN's book they are 46mm, 32mm and 39mm