There is no reason that game should bog down any computer, it isn't intensive in any way. The graphics are simple, the music is simple and annoying, and it isn't using (to the best of visual estimates) any sort of physics engine. That should give smooth graphics on high quality on all but the worst of computers. I would assume you have some kind of compression issue, either that or you have the game(though functional) running in a very inefficent way. Change it and resubmit. It's missile command, not exactly rocket science, pardon the pun.
As far as other things go, as I said the music was kind of anoying from the start, a mute button would be nice. Your city looks like a bunch of crystals. and everything is just a black background. it is not very visually interesting. The gameplay is simple (aka missile command). I think fixing the lag and adding more interesting visual elements would help set it appart, as it stands it is no different than any other missile command game except that it has lag.