I started on this game in 2013 and (pause to run my line count program) have created 296,756 lines of code. Thats over 10 million characters (yes I've changed keyboards).One of the most amusing things about creating a program so large is that the game systems start to interact in surprising ways. Back when I added beds to the game I programmed the dwarves to find and sleep on them instead of the ground. I didn't realize at the time that the animals AI still used some of the dwarf AI code.
I ended up with the situation below.
So I go to test the fence code and watch as a deer casually walks up to the gate and proceeds to tare it down in one kick! He then proceeds to help himself to his fill of crops and then casually walks out over the wooden splinters that remain of the destroyed gate.
Unexpected emergent behavior like this is great fun. I'll leave you with a picture of another deer flexing his (unintended) ale drinking code.