Yahoo is trying to become one of the smartphone cool kids

When Marissa Mayer became CEO of Yahoo three years ago, the former Google executive staked her reputation on one thing: bringing Yahoo, an ailing pioneer of the early Internet, into the smartphone age.

To that end, Mayer made one of her biggest moves just over a week ago, unveiling a mobile app called Livetext, a video-chatting service aimed at teens. It's only the second brand-new mobile app the company has introduced during her tenure.

If Livetext is Yahoo's play to win over young people, then their reaction is key. I decided to check personally with two of them: my nieces, ages 18 and 19. Both of them are avid Instagrammers and Snapchatters.

I used old-school technology, texting them to ask if they'd heard of Yahoo's new app. They responded immediately: Neither of them had -- which is fair; the app was only a week old. I explained what it is: a cross between texting, Apple's FaceTime video chat and Snapchat.

One of my nieces was hesitant. "Idk teens are used to having those things be separate," she wrote. ("Idk" is Internet-speak for "I don't know.")

The other was a little more open to the idea. "That's kind of intriguing," she said.

Obviously, neither seemed overly enthusiastic. But lucky for Yahoo, things change quickly in teen world. I'll ask them again in a few months.

The mission for Yahoo is clear: Convince people -- especially young ones -- that Yahoo is the app to tap when they pull out their phones. If the company can do that, it will be able to get marketers to give them their ad dollars to reach the elusive demographic. The company also reportedly has a minority stake in Snapchat, and Yahoo's 2013 acquisition of Tumblr for $1.1 billion was largely seen as an attempt to buy hipness among young people.

With Livetext, people connect over video and chat using the cameras on their phones. But just as Snapchat has its self-destructing messages and Twitter-owned Vine has its 6-second rule, Livetext has its own schtick: video chatting with no sound. Yahoo says the lack of sound allows people to be less inhibited, as when they are texting ordinarily.