You play it for the gameplay, right? And
Confidential Mission is fun. Its a good little shooter, and coming in at around 20 US dollars, you can't beat it. There are 3 Missions to progress through in the arcade conversion, and each is quite lengthy. Much like
Zombie Revenge and the like, if you die and you have used all your Continues, that's it. You can save your 'progress', meaning your high score, however.
There is also a comprehensive training area called Agent Academy and it contains some 30 different levels and this adds a lot of extra gameplay to the game, as well as Another World which is a modified version of the standard Mission Mode. 1 to 2 players can join in on this one, so there's more than enough good stuff to keep you busy here.