Has a tendency to get frozen certain places, which is the score killer. The first place this started happening was in the saloon with the two floors you could go between via a door. It also happens in the army level specifically when fighting the green beret almost always, unfortunately.
Enemies don't fall down or disappear when they die but instead remain on screen, as well as any points or bullets picked up/etc will still display the point totals on screen and once you kill everyone you cannot advance. This is of course once this bug triggers. You can quit the game and come back into it, losing whatever progress (you can do this from within the game itself fortunately, by clicking off the game, then clicking quit on the menu that appears).
Clearly this game was not adequately tested prior to release. Although graphics-wise and sound effects wise and music-wise it is very good, and the idea itself is good.