Video game design as a hobby?

I’m really interested in developing my own video games. I already have a number of ideas never explored before by other game companies. I don’t plan on it being my career and am already working toward an engineering career. However, once I begin my engineering career, I would like to design and possibly develop my own games as a hobby. How should I go about doing this? After I graduate as an engineer, should I go back for education in computer science or whatever? If so, what major would it be listed under? If more college isn’t necessary, then what can I do to learn what I need to know about designing and creating games? Thanks for any help.