I support you, Gungkwon :) Write code based on the lecture content while being conscious of it. It may be slow and you may feel impatient at first, but if you keep applying it, you will complete a clean and easy-to-understand code that anyone can see. If you are not familiar with it yet, don't try to write it perfectly from the beginning, but it is also good to write and modify the code step by step. (There is no perfect code anyway. When you look at it next time, you will wonder why I wrote it like this.) If you are going to modify the source code of an existing project, First, change the variable names to meaningful ones (This is especially recommended when the code is so messy that you can't even tell where to start and how to change it.) If you changed the variable names, remove meaningless value assignments or (useless) temporary variables. If you take these small modification steps that seem meaningless at the moment, you will find yourself adding more parts to modify one by one. If you are not satisfied with the project code even after modifying it step by step and it is different from what is explained in the lecture, and you no longer have a sense of what to do, it may be due to the limitations of the design. In this case, since there are limitations to modifying the code level, you need to modify it in larger units at the component level. Here is a tip: Do not start without thinking, (The more complex the source code is), divide the entire source code into several large steps (don't worry about the details) and start. You can also draw a picture. Thank you for the good review :):)