I've been reading up on this subject lately, and I found out that you can create your own for certain games.
You see, I just got a Japanese copy of Jurassic Park for the Mega Drive, and I'm getting the warning message produced by the region lock.
Is there anyone that knows how this whole code thing works?

I know that a rom is required to create the code, but I'm not about to get into talking piracy.

Thanks for any and all information you have!