Call it the "second-screen" Super Bowl.

About two-thirds of smartphone and tablet owners use their gadgets to do things like text or post on Twitter while watching TV, according to the Nielsen research firm. So for Sunday's game, companies from Coke to Chevy are trying to reach fans on all the "second screens" they have.

Chevrolet rolled out the first Super Bowl smartphone app that allows watchers to enter a contest to win everything from pizza to a new Camaro.

Kia is the first company to show its Super Bowl ad ahead of the game in movie theaters.

And Coca-Cola set up a Facebook page so viewers can see its animated polar bears - one cheering for the New England Patriots and the other for the New York Giants - reacting to the game in real time.

Advertisers have big incentives to stand out. With more than 111 million viewers expected to tune in, the Super Bowl is by far the biggest stage for marketers. It's also not cheap - NBC is charging an average of $3.5 million for a 30-second spot. And the competition is fierce: There will be more than 70 TV ads during the Super Bowl battling for attention.

To create buzz, it's no longer enough for marketers to get people talking at the water cooler the next morning. They also want to engage the people who like reacting to big events like the Super Bowl by posting on Twitter or Facebook or texting their friends.

"People are glued to their digital devices, sometimes sharing far more that way than they are with others in the same room," said David Berkowitz, whose digital marketing agency, 360i, created Coke's online Super Bowl campaign. "Being social means something very different now."

About a dozen companies have put up their Super Bowl spots on video-sharing website YouTube this year, up from a handful last year.

And USA Today's Ad Meter, which ranks the popularity of ads, is for the first time allowing viewers to vote for their favorites on Facebook.

In its ads, domain-name hosting site will feature a QR code, a black and white two-dimensional code that people can scan by putting their smartphones up to the TV so they can go to the company's website. This is a first for a Super Bowl ad.

Chevy's free smartphone app for the Super Bowl, called Chevy Game Time, allows people to enter a contest to win prizes from Chevy and other Super Bowl advertisers. Users also will get a code. If the code matches the license plates in Chevy ads during the game, they win one of 20 cars being given away, including the Camaro, Silverado and Sonic. App users can answer trivia questions or polls to win prizes.

Other advertisers are going after the laptop and tablet crowd. As part of Toyota's Super Bowl campaign to showcase its "reinvented" Camry, the company is asking Twitter users to use the hashtag or search term "#Reinvented," to post or "Tweet" about what other products should be reinvented. Some will get a response back with an illustration of the "reinvented" product.

Volkswagen released a teaser of its 60-second Super Bowl ad on online. The ad, which shows dogs in "Star Wars" costumes barking the "Imperial March" song, was released Jan. 18 and has 10 million views.