Slow and slower

Clever Idea for a game but awful implementation.
I am running this on a 2012 iMac with 8Gb ram and it works fine for maybe 10 minutes at a time then I have to exit and restart it due to incredible laggy, almost frozen, response that makes it unplayable. It has also crashed a couple of times in the approximately 5 hours I have been playing it.
It seems incapable of running at a usable rate when there is lots of action on the screen, I can predict when it is going to be too slow to be usable and it is repeatable at the same points each time.
As a comparison running an old half-life2 game on the same machine is about 10X faster.
Just glad I didnt buy it until the price dropped - I wont be buying any more of this companies products

Chriszzz123 about Darkest of Days