Hard puzzle is a page where I put puzzles a little more complicated than how many squares you see in the drawing or what color is the red car.
The course based on a well-known book "Automate the boring stuff with Python".
Course on structural and creative design patterns. In this course I have also included an introduction to design patterns.
Course on behavioral design patterns. I am also considering anti-patterns here.
A course with various aspects of mathematics to remind them programmers or future programmers.