If you want to take notes, you will record the main points of knowledge points on the left side of the notebook, and mark the key points or difficulties or difficult to understand with a red pen, while the left side can be the typical application of these knowledge or the analysis of error-prone topics. Personally, I think we should omit the appropriate pen, try to use two-color pen first, and then stick to the application topic or error-prone topic of the note. I hope it helps you.

Typing is not easy, adopt it!