I bought several courses from Inflearn, and they were as high-quality as Toby and Kim Young-han. When I learned object-oriented code from a book, I didn't understand it well, but when I performed the refactoring process one by one through practice, it seemed easier to understand. There are still some difficult parts, so I think I need to practice by repeating them until I can refactor without looking at them... The course was really helpful after I took it. I liked it so much that I bought the 'Test Code' course in advance, and I plan to take the test course after I finish the refactoring practice. Thank you for providing such a good course.