Public Service Announcement
If you are currently using Pretty Good MahJongg Mac Edition, whether purchased from the Mac App Store or downloaded directly from Goodsol Development, we recommend waiting for the next update before upgrading to macOS Sierra (10.12).
Do Not Upgrade (yet)
Apple is scheduled to release macOS Sierra, the next version (10.12) of their operating system (formerly: Mac OS X) today [September 20, 2016]. As of the final beta version, there is a change (as yet unidentified) that breaks Pretty Good MahJongg Mac Edition. We are actively working on a solution, and we will publish an update as soon as a fix is available, but in the meantime, we suggest keeping El Capitan (Mac OS X 10.11).