Lines of single_doc/三个残局代码遗留问题.md from check-in 57b8fe70da that are changed by the sequence of edits moving toward check-in 6f3a61445a:

                         1: # 三个残局代码遗留问题
                         2: 
57b8fe70da 2024-06-29    3: ## 不要用 DEFENCE
57b8fe70da 2024-06-29    4: 
57b8fe70da 2024-06-29    5: 现在该用 DEFENSE