In practice the sticking point tends to be code. Someone at some point will ask you whether any of your code was written while at your prev employer, and you h

In practice the sticking point tends to be code. Someone at some point will ask you whether any of your code was written while at your prev employer, and you have to be able to say no. No one seems to ask about ideas, because that's so much vaguer. If you get an explicit carve-out for your side project, you're ok. Companies vary about those. Google seems to be very accommodating, more suitish companies less so.