Apple have released their next version of the Mac OS Catalina 10.15. This is a major update for Mac gamers as Apple have dropped support for 32-bit applications and you will only be able to run 64-bit apps on Catalina.
How does this affect me I hear you say?
Well, up until this point games were designed to run on a 32-bit OS, these games cannot run in a 64-bit environment, they were not designed for it. If you have upgraded to Catalina you'll likely find some games no longer work along with some Mac apps.
What can I do to avoid breaking my game support?
The only thing you can do is remain on Mojave for now.
What if I've already upgraded?
All is not lost, you can freely reinstall Mojave at any time, however, you will need to wipe your mac to do so, instructions on such a process can be found online.
Alternatively, you can install boot-camp and side load a copy of Windows on your Mac to play the game, More information can be found here.
Can I upgrade to Catalina in the future?
You can as many publishers will update their games to support Catalina, however, many games no longer see updates and as such will never support Catalina or newer Mac updates so you may need to pack those old games into a cupboard and forget about them if you want to upgrade your OS.