Being a shooter the in-game effects mainly consist of shooting and explosions. In Dolby Surround mode the explosions actually seem to come from different points in the room and as you fly past the enemies the shots and effect sounds actually travel from the front to the rear. It is quite an experience listening to the sound as the developers intended, if you don't have a Surround Sound system you're really missing out on something since you're just not doing the game justice playing any other way. Playability Viper is about as custom-made as you would want a shooter to be. In most shooters, the difficulty level usually effects the number, speed and type of enemies that are present.
Viper introduces a new twist.
The difficulty level you select effects not only the enemies but more obviously the type of helicopter you are flying. On Easy level you are armed with a very fast, agile and heavily armored bubble chopper. On Medium you are in a bigger, slightly slower, and less armored chopper while on Hard you are flying a behemoth sitting duck with very little armor and handling like a truck. This is a nice little twist on the difficulty levels since it essentially give you three different flying styles and forces you to adapt depending on which setting you have chosen. Once in the game, the flying style is very similar to G-Police.