Here’s my solution (it’s the one from the book):
And here’s the link:
http://www.lodev.org/jstumble/?board=11lllir1lflxfrlrflereereeleelereereeleelerf
Description: The left 2 bits act as a register counting down from 3. The 4th ball heads over to the right flipper, releasing a single red ball. The first red ball just heads back over to the blue side, starting another countdown from 3. The second red ball lands in the interceptor.