Hi @galleon
Welcome to the community!
Check the following link
If you define the rectMode to CENTER then all rectangles have their origin in the center, which allows you to draw the square within a square much easier!
Concerning the questions on
What would be the best way to repeat the same ensemble of shapes on a regular grid pattern ?
I would say to create a class of an object with this drawing and then repeat the pattern over a grid.
I wrote a similar code in this post on the forum:
Hope it helps! And let me know if you have any questions or doubts! I will try to explain or make a simpler example for you if needed
Best regards