Hello. We've just tried PONDSCUM demo and we're not sure that the game runs fine. It's too fast and it's hard to understand there you are.
can you please try holding F1 - this will print the FPS in the lower left corner - it should be 60. i've been told the game does run at double speed on some high frequency monitors! (though pondskum mode IS quite confusing and hard to see where you are in :))