I was a bit worried because Udemy and other sites were selling 30-hour lectures for 20,000 won, but I bought it because the quality of the lectures that were available for free was good. First of all, it was good because it was in Korean, and compared to mass-produced lectures that just clone one web page, there were many traces of efforts to incorporate practical perspectives and organize it in a well-organized manner with a clear goal, so I give it 5 stars.