It's pure copy of Nine Men's Morris board game. It was easier for me (and still is; there is still long way to go for me to design new games) to use existing games as a core or entire project. It should've been easy to "convert" it into digital format due to its simple board and rules. I just had to use that thing in my head called "brain".
Oh well, everybody has to start from somewhere, right? XD
EDIT: Even today, I still find myself not utilizing what C# has to offer and instead rewriting massive pieces of code. I passed several times over the code of Battle City and found numerous situations where I could (and did) eliminate copies of code and replace them with one or two methods which do the same job, but better. In the above code, all that placement could easily be summarized into 1 void method with 2 to 4 parameters, instead of doing massive if...then...else if.. tree which is insanely hard to read.