reviving this again with a bit of a mockup of what i remember the game looking like, kind of.
the game has been found :D
it is Adventure on the Atari 2600.
no idea why i was playing it on a Macintosh but i know for a fact we never had an Atari.
i'm actually surprised i forgot about this one, because it's quite notable for containing the first ever easter egg.
I have taken this to the r/ClassicMacGaming subreddit to see if anyone knows about it there. Hoping!