Joey Flynn is the designer behind Facebook's Timeline for mobile, which means he works on one of the most popular apps in the world. His hands are on everything from the way your mobile profile looks to the way it reacts to your taps and swipes. And he's a really funny guy, too. Flynn took a few minutes to talk to The Verge about the challenges of designing for a tiny screen, hearing people talk about you behind your back, and even about his muse, children's horror author R.L. Stine. You can find Flynn on Facebook here.

So you've built an app that hundreds of millions of people use. How does that feel? Don't be shy.

It feels pretty good to work on products that so many people use. It's always funny when I'll be out at a restaurant and the waiter or the table next to us will be praising or cursing a product I've helped out with. Or when you see a someone taking a photo of their friends and they're all yelling "cover photo!" or "profile pic!". With popular products you end up getting a lot of accidental feedback.

"You need to be super intentional about putting anything on screen when the screen is the size of a credit card."

You once told me that Facebook's Timeline feature was originally experimented on as a horizontal version as well as a vertical version. How do you see our social lives being mapped online ten or twenty years down the line?

Oh man, tough question! Think about what was going on 20 years ago! It's crazy how fast everything changes. To (kind of) answer your question though, I don't really think that far ahead. Both people and technology are going to change so dramatically in 20 years that if you could predict it, well, if you can predict it give me a call and tell me what it is like: (650) 52...

Aside from Facebook, which is your favorite social network to use?

I have a big group of family and friends who are pretty active on Instagram so I end up checking that pretty frequently. I'll also read Twitter a couple times a day.

Are you still using an iPhone? From your perspective as a mobile UI designer, what do you think of the iPhone's 3.5 inch screen? Should it be bigger, or a different aspect ratio as some have been speculating about lately?

Yep, still iPhone. I actually think the screen size is comfortable and I find the aspect ratio to be pretty nice. I've spent a lot of time using both larger and smaller phones and they always feel a little clunky. Except the Sidekick II. That phone was sick. AIM all day.

What are the biggest challenges of designing for a small screen?

The biggest challenge is just that, a small screen. You need to be super intentional about putting anything on screen when the screen is the size of a credit card.

Another consideration is how these decisions translate to other mobile platforms, mobile web, tablets, and the desktop. For Timeline we worked on both the mobile and web versions at the same time so it allowed the two to inform each other. If you just translate a web product directly to the phone it quickly becomes apparent that it doesn't really work. For this reason, 'mobile first' just seems to make sense. It requires you to be a strict editor when architecting a product on a mobile device and then allows the interface to kick back and relax a bit when you bring it to a tablet and computer.

"Wanting anyone in any situation to have the best possible experience is a really tricky problem to solve."

What are the biggest challenges of designing/scaling for a social network with hundreds of millions of users?

The biggest challenge here is that you have no specific audience. Your audience is everyone. For mobile specifically, we have different types of people using different apps on different platforms on different sized devices. Wanting anyone in any situation to have the best possible experience is a really tricky problem to solve.

Nicholas Felton cited your "imaginative interactions" (like the Facebook app's live-view camera for shooting cover photos) as a place "where Facebook works best." What other ideas are bouncing around in your head that nobody's yet hit on for mobile? Or for social networking in general?

I do have a top secret project I'm working on where we're going to be using... Whoa! Almost got it out of me! Really though, we've got a lot of exciting things in the pipeline but I have to keep them under wraps.

Which third party apps (apps that don't ship with your phone) are the most indispensable on your home screen?

I'm a big Radio Lab and Fresh Air fan and I use Instacast to manage my podcasts. Scramble With Friends for sure. I also have a few prototypes that I play with quite a bit, but I can't really talk about those.

What's the last great book that you've read? Why did you like it?

To be honest, I'm a bit of a bookworm. I'm really into this little-known American author who's been doing some next-level stuff for the past 20 or so years — R.L. Stine. Two gems of his I've discovered lately are Monster Blood II and Return of the Living Dummy. They're both sequels to great works of literature, but the craft of this author is so honed that you could really pick them up without having read the first books.

Or, seriously, though, check out Damien Hirst's On The Way To Work.

"For me, no one thing really works for staying focused and being productive."

As a designer, which other developers, artists, or architects should we be following? Which ones inform your work the most?

It's actually pretty crazy for me to think about the overlap of whose work I follow, whose work informs my work the most, and who I work with at FB. Felton, Matas, Walkin... those dudes are ridiculous. Outside of that though, I still read a lot about the work of the designers I followed in school — Armin Hoffman, Josef Müller-Brockmann, Helmut Schmid. Their work and philosophy is amazing.

What video game has had the most impact on you as a person? Why?

Well, if you're asking about literal, physical impact, I'd have to say 007 for Nintendo 64 based solely on the time that, after a heated game, my brother removed the actual cartridge and bludgeoned me with it. That was the last time I was allowed to play as Oddjob.

What's your computer and software setup?

I use a 15-inch MacBook Pro. As for software, I bounce between Photoshop and Quartz Composer almost every day. Quartz Composer is this awesome piece of software that allows you to make fully interactive prototypes by connecting different patches together. It's basically like visual coding. Also, any change you make in your composition is instantly reflected in the prototype so you don't have to wait for the page to refresh or your code to build to see if something is working or not. It allows you to iterate super quickly.

I also use LiveView for viewing it on the device. LiveView has "Interactive" mode which works really nicely with Quartz compositions that you want to interact with on the device.

How do you stay focused?

For me, no one thing really works for staying focused and being productive. I'm not one of those people who can just sit and crank through 14 hours of heads-down work. When I am cranking, I drink a ton of coffee, probably an unhealthy amount, and listen to music. I spend a relatively large amount of time every day talking with other designers about my work and about their work, which keeps the ideas flowing and helps me avoid getting stuck in a rut.

Another thing that I've recently been trying is breaking up my work into chunks as opposed to just staying at the office all day. I've been doing some work from the city before I head down to the office and leaving a bit earlier than I used to, eating dinner in SF, and then working some more from home. This gives me some time where I can step away from my work and come back with fresh eyes. It's been working really well.

How do you organize your life? Use any GTD workflows or apps?

To be honest, I'm not the most organized person. I have a ton of workflow, task, and list apps on my phone but I usually just download them to look at the interface and interactions and then they just sit there adding more clutter to my life.

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