In the case of Flex and Grid, I think it is essential to know them to become a front-end developer. I think you can study by looking at the specs in mdn, but I wanted to learn quickly and was curious about how to apply them in various ways, so I took the lecture. There is a part in the middle of the lecture where the concept is explained with odeng skewers, and thanks to that, I was able to avoid getting confused about the concept. The small tips were also good. Since it is a concept that deals with space, I think individual effort is important to apply it intuitively and quickly.