When you need to fill a space, first observe the number that has been filled. For example, if you see a 3 already connected to a line prime on a line, then the next space in that line should be filled with 9 (because the top and bottom complement each other). In the same way, if you check all the occupied numbers row by row, you can quickly draw conclusions. It's not just a speed game, it's a journey of mental exercise.

　　In ancient times, the nine-square grid (also known as "Luo Shu" or "Luo Shu Jiugong") was not only a treasure of mathematics, but also an important tool for enlightening wisdom and training thinking. Mastering and familiarizing yourself with the nine-square grid password will not only bring a lot of fun to your math and brain teasers, but also bring out its unique benefits in everyday life. So, how to better memorize and apply the nine-square grid mantra?