My background is in hardware design. I found hardware work to be a welcome change from thousands of hours of programming and that led to the designs you mentioned.
Looking back, video game design seems a natural fit, although there was no such thing when I was growing up. I built a Tic-Tac-Toe playing machine in my teens which went up in smoke on the night it was scheduled to go to a science fair.
Another little known fact about Amazing Tennis - the computer opponents are modeled after real people. In an odd turn of events, I joined a division 3 college tennis team at age 38.