Hello! Bought and played the game for Mac. Here's a few things:
1.) Had to give it write permissions and run sudo to make save files.
2.) I entered the thicket through the secret garden and the game began to lag relentlessly from that point on; frame rate, key input, etc. It would kind of recover during battles and in small hallways. It was frustrating but I kept playing.
3.) The cube of the deep glitched out (still in inventory and 'usable' but no effect) and could no longer be used, so I couldn't really complete any more puzzles. I gave up at that point.
Enjoyed it though. Hope you're able to work on these issues.