File system navigator in menu bar for macOS.
This version of Drill Down shipped on the Mac App Store for several years and is now available as open source. This is useful as a reference to the system menu API and for building large performant menus on-the-fly.
Drill Down became less useful when Apple separated the hard drive volume in system and data segments. System-installed apps in /Applications were no longer included in the directory listings returned by FileManager.