Operation C is a worthy sequel of the Contra series on the Nintendo Game Boy.
Operation C was released by Ultra Games back in 1991. For those of you who don't know, Ultra Games was a subsidiary company of Konami that released quite a lot of Konami games on consoles such as the NES and Game Boy. Anyways, back to the game, Operation C is a solid plataformer that will give you a few minutes (.... er, hours) of fun gameplay.
The game is a simple, 5 level game that should take you about 20 to 40 minutes to complete. You once again take the role of Corporal Lance (aka: Scorpion) and rush towards battle in order to destroy the Black Viper, an alien bent on completing what the Red Falcon could not do (destroy Earth or something, hehehe). The 5 levels are distributed as 3 side-scrolling levels and 2 over-the-top levels (similar to Super C). These levels are pretty much straightforward with a good amount of enemies to blast away. Most enemies run towards you or stand at a distant and shoot you VERY VERY SLOWLY. Bosses are quite simple too. It takes less than 30 seconds to finish most bosses. As far as weapons go, you have your standard machine gun plus 3 other powerups that you can find floating around the levels (Fire gun, homing gun and spread gun). The music is ok.... it doesn't stand out at all, but it doesn't bother you either. The grapichs suit the game very well. Now, take a second and try to remember a screenshot of Contra or Super C (you can cheat and look it up on Google...). Now, take that picture and imagine it in grayscale and there you have it.
In the end, Operation C si a formidable (yet very short) game. I treasure it a lot and I must say that it is one of the best games in my classic Game Boy games collection. If you still have it, I beg of you, DON'T THROW IT AWAY.