The game runs fine on the machines I tested it on, so I'm not sure exactly what's causing the lag, but I just posted a new downloadable version on the game page if you want to see if that fixes your lag problems. I also added an options menu to the title screen that allows you to switch to a less resource-intensive level of effects, so that might also help the lag some.
Thanks for leaving a comment telling me about this issue, I appreciate it.