* ‘When I use a word,’ Humpty Dumpty said, in rather a scornful tone,
‘it means just what I choose it to mean — neither more nor less.’*

* ‘The question is,’ said Alice, ‘whether you can make words mean so
*

*many different things.’*

* ‘The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.’*

* — Lewis Carroll, Through The Looking Glass*

Welcome back to the teachers out there. Here are a few remarks about Episodes 4 and 5 of the Joy of Code series.

If you have any questions or comments, let me know in the comments section here on the blog, and I will respond to them in the next episode of the teacher commentary.

I think the turn-method turns the wrong way. In mathematics positive angles turn counter-clockwise. In Greenfoot positive angles turn clockwise. This will be confusing for students.

I realized that the y-axis is pointing downwards and that means it’s as if you are seeing the coordinate-system from the other side and up-side down, so it’s consistent that positive numbers turns clockwise.

Yes, I agree.

However, we had extensive discussions about having the y-axis go down. We were considering for quite a while to have the more traditional (in maths, anyway) origin-in-the-bottom-left arrangement, with the y-axis going up. However, almost all computer systems do it this way, and finally we decided to be consistent with other computer graphics systems, rather than with maths.