Lego-Duplo letter brick

__Update (2018/11/18) :__
-Added digits
-For all bricks, I created a "thin" version (half standard brick height) : letters are easyer to manipulate, and print time is greatly reduced.

__Original text :__
This thing contains a whole set of letters, from A to Z, upper and lower case.
I will add digits and some other letters later.

In Montessori education, you shall print vowels and consonants in different colors (for example blue and red) in order to help the child make the difference be