Pure CSS tree

1. Folder 1
   1. File 1
   2. Subfolder 1
      1. File 1
      2. File 2
      3. File 3
      4. File 4
2. Folder 2
   1. File 1
   2. Subfolder 1
      1. Subfile 1
      2. Subfile 2
      3. Subfile 3
      4. Subfile 4
3. Folder 3
   1. File 1
   2. Subfolder 1
      1. Subfile 1
      2. Subfile 2
      3. Subfile 3
      4. Subfile 4
4. Folder 4
   1. File 1
   2. Subfolder 1
      1. Subfile 1
      2. Subfile 2
      3. Subfile 3
      4. Subfile 4
5. Folder 5
   1. File 1
   2. Subfolder 1
      1. Subfile 1
      2. Subfile 2
      3. Subfile 3
      4. Subfile 4