You can enter the folder using `cd ae216~1`. Try to create some files. Then use `dir` to check. Exit the directory with `cd..` and then `md a`. Now you can open that `a.`. You will find it is empty, but it's a trick. Only by using commands to check the `a.` directory can you see the files. Haha, I said that after `md a`, you can access `a.`. Now try deleting `a.`? The folder `a` will immediately become `a.` and contain the original files inside `a.`. Of course, you can only see them by using commands. It's super interesting. A new kind of "explosive" is born. Of course, playing with explosives is okay, but don't harm others.