The Super Bowl commercial blitz is extending beyond the usual talking babies and office chimps to engage viewers online and get more for advertisers’ $3 million-plus investment. Marketers are using every trick in the playbook to dominate the buzz before the game and long afterward, too. The gimmicks include online contests, a car “race” powered by Twitter mentions, and a secret new level of a hit iPhone game. The goal is to build buzz, not get lost in the 42 minutes of Super Bowl ad time, and get cheap or free exposure when viewers watch again on YouTube.