While most teenagers spend their Sundays catching up on homework, high school senior Christina Gee has spent the last few months helping build the next Snapchat. She serves as one of several teen advisors to Squawk Messenger, an app launching in the App Store today on iOS. Gee offers insight on everything from read receipts to GIFs to "ephemeral" exploding pictures and text messages with one question in mind: would she and her friends actually use the app to talk to each other?

Since the meteoric rise of Snapchat, tech pundits, venture capitalists, and startup founders have tirelessly attempted to decode its winning formula. Squawk founders Chloe Bregman and Alex Karweit turned directly to the trend-setting oracles that helped launch Snapchat — students in San Francisco — to trade experience working at a startup with vital teenage insight.

For example, at first glance, Squawk isn’t outwardly handsome in any way, shape, or form. But that’s actually on purpose. Bregman attributes some of Snapchat’s success to its "informality" — it swaps polish and pixel-perfection for friendly colors and customization. "Snapchat isn’t perfect looking, which made it approachable," she says. "You don’t have to be serious when you’re using this thing." Bregman learned lessons like these from Gee and a student advisory group turned intern class that met every Sunday for the last several months to provide feedback on a beta version of the app.

The final version of Squawk is the most complete ephemeral messaging app we’ve seen, and it’s fast. It includes the ability to send texts, photos with captions and Aviary editing tools, voice memos, animated GIFs, stickers, and even a "selfie" button — all of which can be set to "self destruct," just like a Snapchat message. Additionally, the app offers various degrees of customization: the ability to change a conversation’s background, your own chat bubble color, and the header image on your profile. Each user’s profile also includes their name, school (an interesting detail), email address, and "5 Things You Didn’t Know About Me." Squawk, like Facebook, operates on the "friending" model, though that’s where the similarities between the two social utilities end.

"The consensus we found was that when an app has Facebook in it, it becomes shady," says Bregman, who decided not to add a Facebook friend-finding feature after heeding the advice of her teen advisory group. "When you connect with Facebook, there are so many privacy pop-ups that it makes it unclear what Facebook’s actually going to do," she says. Bregman’s teens asked instead for the ability to see another user’s friends list, which they could use to find other people they might know. These apps do, after all, grow virally — from friend to friend and group to group — and Bregman feared that adding your entire Facebook friends list from the get-go could get messy anyway.

"These people really care about our perspective, and what we had to say," says Gee. "At our first meeting, one of the things we discussed was if the background should be customizable by person or if you should share a background." Gee and her peers eventually decided that being able to change the background wallpaper of any chat conversation would be interesting, and would enable you to share long-running inside jokes with friends. Her favorite feature is the app’s self-destructing text messages. "During prom when we were trying to figure out who we all wanted to ask, we used auto-destruct messages," she says. "Then we didn’t have to worry about it being seen by other people." Snapchat, in contrast, only allows self-destructing photos watermarked with at most one line of text.

Bregman’s focus group has offered a lot of insight into building an app, but also into one of the prevailing questions of 2013: why are teens afraid of media permanence? "I’ve had Facebook since seventh grade, and photos are now surfacing that I kind of wish I never posted," says Gee. "I wish I would’ve had a setting to make something permanent or impermanent." As a teenager whose identity is "always changing," she doesn’t want photos and texts that will stick around forever. Squawk offers the ability to send all sorts of media, like GIFs you’ve copied from the Tumblr mobile app, or animated stickers handmade by the company, and then get rid of them forever. The company promises from the get-go that all exploding messages actually leave their servers for good.

Bregman and Gee may have produced an app that’s perfect for teens, but their teamwork yielded an odd conundrum. "Authenticity is more important than what’s cool," Bregman’s discussion group members said loud and clear. The next test is whether an app made with the help of teens, for teens, is really what teens even want. "In theory, it’s uncool this is an app made with help from teenagers," she says. "Your article could actually make us uncool. That’s the paradox of it."