Starry Night is a port of a Windows from-scratch (thanks to Evan Green) recreation of a Berkeley Systems After Dark classic module. If you enable "Retro Colors" (e.g. grayscale) and squint a bit, you can pretend your Mac has traveled back in time and become a Mac Classic.
Uses Cocoa drawing calls that should work on any Mac running Mac OS 10.5 or later
Note that in preview mode, the screensaver doesn't currently take into account the smaller view and draws the same number of buildings that would be drawn in the full screen mode, so this may not be an accurate preview of the generated building layout.