This was a huge hit when it came out, and when you think of the lack of features it makes you wonder why it was such a popular game.  Probably since the movie came out around the time Rambo was in the theaters probably added to the popularity, but this is a shooter that scrolls upwards.  You can shoot in either different directions with your machine gun and throw grenades.  Only problem is that the grenades only go in the up direction even if you are facing another one and there are no upgradable weapons, so you better get used to that machine gun becase it is all you got.