I think maybe it's a v-sync issue? If I lower the resolution enough to get 60 FPS, the medium and high settings are perfectly smooth. If the frame rate drops below 60, I get awful hitches. (Unfortunately there's no wide-screen resolution option low enough for my PC to get consistent 60 on Med/High). Also, weirdly, if I try to force v-sync through the control panel, I get low frame rates and hitching even on the low setting, but as soon as I go into the game's menu, the frame rate shoots back up to 200+ (Forcing v-sync OFF through the control panel doesn't seem to work, or at least has no effect on the hitching at Med/High.)
Not really expecting technical support for a little game like this, but thought maybe you'd be interested. Thanks again for making it.