Thanks ThomThom for this awesome tool.

I managed to make it work in Sketchup 2018.

• Download Citelum's GitHub archive (thanks for uploading it!)
• Unzip it in your Plugins folder (for me C:\Users\YOURNAME\AppData\Roaming\SketchUp\SketchUp 2018\SketchUp\Plugins)
• Edit Plugins\citygen\modules\bldg_gen.rb, add a # before : require 'offset'

Cheers!