>.... except for those inventions that ... [r]elate at the time of conception or reduction to practice of the invention to the employer's business, or actual or demonstrably anticipated research or development of the employer

Seems pretty clear on the "similar business" front. IIRC that's been the wording in many if not most of the contracts I signed while I was still working as an employee in CA.

I've mostly worked in games, too, and so that pretty much meant "no game dev in my free time," period. A strong motivator to go indie/consulting.