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You won't be able to play natively, but you can maybe create a VM, and run old 32bit version of OSX that way. I don't think performance will be very good, but that may work
 
It should also be noted that Oni is a 25 year old game and even in emulation it should run insanely well.
Also with some of the cheat codes it opens up the game in a whole new way, and getting to explore areas of the map that were previously inaccessible.
 
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