seems something is wrong with either your time sampling or performance, because I get rather jerky movement when playing the breakout or the chase demo. did you notice that too? No, it was always smooth for me. But I only tried it on 64-bit machines and only with ghc-6.10.2.
at what rate are you sampling? if you are sampling at a lower rate as the video vsync, you might want to perform interpolation between two "logical frames" as jules bean did in his own reactive planets demo. The breakout example has a zero threadDelay in its main loop, because that apparently causes a break with the length of a scheduler tick, essentially giving an 50 Hz sampling rate. The chase example has no delay added at all, and it goes over 2500 fps for me.
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