I am writing to a friend of mine and I can't find a proper word to describe two language-learning courses in Duolingo.
As for the Duolingo German and Spanish courses, I find them to be ...
The message I want to convey is that I think that they took care of every detail while they were making them.
Would you simply say well-made? Is there a more proper term to use to talk about the act of caring about the details?