I am having serious issues with the framerate that is unstable and drops to as low as 20fps starting from the first stage.

Saw other posts recommending to edit a boot.txt and setting "no_vsync 1" (default is "no_vsync 0"). I actually had to create this file as it does not exist. This did not help. Played with resolution and lowered the quality without any improvement.

I am running Steam through Whisky on a M3 MacBook Pro with 18G of RAM. So far I did not have any problem with other games (mostly 2D such as Mushi and Shadow of the Ninja Reborn).

Any idea on how to fix the problem?