Unfortunately, when you try running certain games on a mac, on a case sensistive HFS+ filesystem, you might hit a roadblock.
Steam itself will run fine.
Fortunately there is a solution by using OpenZFS. I won’t go into the details of installing ZFS on a mac as there is plenty of information out there. I simply use homebrew for that kind of thing. Refer to the OpenZFS Wiki, they have instructions on how to install using homebrew.
Method for Creating the Filesystem Image
OpenZFS supports creating a pool inside a file, so this is what we are going to do.
mkfile -n 5g steam_disk.zfs zpool create -O casesensitivity=insensitive steam_pool /Users/$USER/steam_disk.zfs
Then you will get a shiny new volume with the required properties under /Volumes/steam_pool/. Fire up Steam, tell it to install there.
Enjoy, and don’t forget to read up on ZFS basics if you don’t know how to export and import a pool.
zpool export steam_pool zpool import -d /Users/$USER/ -a