I am interested in being just a battle programmer. I would assume that this is a position in game development companies. What sort of portfolio should I build up? Is it even worth attempting to become a battle programmer since I am 31 years old with no prior "professional development" experience.
Battle & Fight scenes have always seem to get my attention and is the coolest part of almost every game (for me). My favorite "Battle" scenes would be the ones in the God of War series.
Thanks..
As a major advice: do not become a hyperspecialist. Even if you specialize in gameplay programming, and specifically "battle systems", if that's all you can do, your chances to get into the industry lower (especially if you have no prior experience in the industry).
Hyperspecialists are usually hired "on-point", due to their previous experience, for a limited time in the project, for a specific task in the project. For breaking into the industry, versatility is a trait that's most beneficial for programmers. Even if your main passion is battle system programming, if you are asked by your project lead to fill in in other areas (other gameplay programming, AI, graphics), and you turn him/her away saying "I can't do that!", it reflects bad on your abilities.
If you want to have a permanent employment, and be at the company as an employee rather than work-for-hire, be prepared to do many different things, as project needs come. A battle system programmer would not be needed for the entirety of the project, so what would you do with the rest of your time? If you don't do anything else, producers might start thinking paying you to wait is a waste of money.