Last time I used a Mac was before 10.14 so I'm not sure if there are any compatibility fixes to run 32bit apps nowadays (steam forum would absolutely be a better place for that), but you could use something like Boot Camp to boot into an older version of MacOS (or Windows) when you want to run BattleBlock, and then switch back again. Or if your computer is good enough for it, maybe an old MacOS/Windows virtual machine in Parallels so you don't have to keep rebooting? I feel like Boot Camp would be easier but it just depends how impatient you are xD