Operation C is a Contra game that not many have heard about, yet is one of the best in the series (at least in my opinion). Because this game is not a handheld port of another Contra game, it does not try to mediocrely emulate console quality gameplay. Instead it is its own unique creation with amazingly designed levels and graphics. Operation C does bear some resemblance to Super C since Operation C came out a few years after; the main similarity being the top down levels. Like all Contra games, the difficulty does not fall short. In my opinion, Operation C has the best boss enemies compared to the original Contra and Super C. Operation C was the first Contra game to add the homing gun power up, and removed the worthless laser power up. The story premise is exactly the same as pretty much every Contra game out there: Aliens invade Earth yada yada yada and you have to kill them. The one problem with this game is that there is no multiplayer. It probably wasn't possible/practical anyway with the Gameboy's hardware.
Here is a video of someone doing a longplay of the game: