You are welcome.
In the very old days I used to design filesystems for a custom kernel. UNIX was so much easier to follow than things like the old DEC RSX filesystems. Current filesystems are becoming as complex (BTRFS is almost the same - it lacks file versioning, but has additional features). But the underlying principle still remains.
Directories are now keyed files instead of simple linear lists (allows faster updates, searching directories with lots of files)