Hello, everybody. My name is Mike Stern, and I'm User Experience Evangelist at Apple. And it's a great pleasure to be with you today to talk about designing for Apple Watch. Now, in today's session, we'll look at how to apply design best practices and leverage the new capabilities of watchOS 3 to design Apple Watch experiences that are fast, focused, and delightful. But before we get there, I want to start with some basics. Now, after all, some of you may have never designed a watchOS app. There are three basic components to an Apple Watch app; complications, notifications, and apps.

A complication is like a little widget that people can display on their watch face. The term complication comes from traditional watchmaking, and it refers to any feature on a timepiece beyond the display of hours and minutes. Complications made the design, manufacturing, and repair of watches more expensive and more complicated, hence the name. Now, fortunately for you, complications are far easier to make for Apple Watch and they're way more powerful.

Complications on Apple Watch offer the quickest way for people to access information and provide a really fast way to get to apps. Notifications tell people about significant events that they might otherwise overlook. And because they're also interactive, they're a great way to push interactions to the people who use your app. And lastly, apps offer a deeper experience with your product or service. Now, providing a complication or making watch-specific notifications requires you to also have an app.

These three basic components are designed to work together. Each plays an integral role in the overall user experience of your watch app. So, for example, let's say that I'm ordering dinner with my watch. I might start out by tapping a delivery app complication to launch the app. I then use the app to place an order. And after doing that, I would probably receive a notification with a time estimate about when my order will arrive. While I wait for my food to arrive, I might periodically check the complication to see how much longer I have to wait.

And when my order is about to arrive, I might get another notification letting me know. And finally, if I hadn't already tipped the delivery person, I might get a notification asking me if I would like to do so. So that's the basics about the components. Now this presentation will help you to learn how to design each of these well. But before we get there, there's something even more basic, even more fundamental, that I'd like to discuss with you. And that's the concept of time.

Apple Watch was specifically designed to support lightweight interactions, meaning that people should be able to get information and take action in very, very short amounts of time. Now I suppose this is an obvious point, but it's really easy to lose sight of this. Of just how quick interactions need to be when you're designing comps or testing your builds in simulator. Now as you design your app, always challenge yourself to find faster and less complicated user flows. There's always a way to optimize.

For instance, many of our built-in apps have been made simpler and quicker to navigate. Previously, starting a workout required you to go to the Home screen, find and launch the app, select a workout type, pick a goal or reuse the one that you used last, and then tap Start.

The new flow is much simpler, especially if you use the workout complication. You just tap the complication, then click Start, and you're off. Now Quick Start lets people bypass the screen for selecting their workout goal and removes the need for a separate Start button. Now most people workout the same way, day in and day out.

So, for those people, it just takes two taps to start a workout. And the UI shown while you're working out has also been optimized for faster interaction. Previously, there were seven screens that people could swipe through. One for controls, and one for each of the workout metrics. And navigating between these screens required just way too much time.

In watchOS 3, there's just two screens; controls and metrics. There's basically no need to navigate until you're done with your workout or if you want to take a break. Now this frees people up to focus on what's most important while they're going for a run or riding their bike. Focus on your cadence, your pace, breathing.

Look out for cars, pedestrians. Enjoy the scenery, and try to look cool. With watchOS 3, the Apple Watch design and engineering team rallied around three important themes for this release which I think are relevant to us all. Those themes are glanceable, actionable, and responsive. Glanceable means presenting information so that it's immediately comprehensible. Your design must communicate clearly and without distraction. You should only display the information that's most relevant.

Ideally, the information that your app displays is also actionable. This means inspiring people to take physical action in response to what your app communicates, or making it easier for people to access functionality from your app or notifications. And apps should be responsive. Launch times and screen loading should be kept to an absolute minimum. Content and data should always be up-to-date, and UI feedback should be immediate.

Now to help your apps be more glanceable, actionable, and responsive, major changes were made to the navigational model and core architecture of watchOS. The new Dock provides people with a browsable collection of timely and contextually-relevant moments from their favorite apps. Apps in the Dock are kept in memory and can periodically perform background updates, which means that navigating to an app from the Dock is fast and people will spend less time waiting for app content to update. And once you're in an app, you can now move directly between detail screens, which greatly reduces the time spent navigating. These changes can significantly decrease overall interaction time. In fact, with watchOS 3 our internal target interaction time was reduced from 5 seconds down to 2.

Now, admittedly, the first time I heard about this, I thought, "That is pretty ambitious." I mean, it literally takes me about 2 seconds to say the words "2 seconds". But, the truth is that performing tasks like checking scores for a game, or checking the weather, or checking stocks can and should be that quick.

Now, throughout the day, you might spend way more than a few seconds checking the weather, scores, or stocks. But each of those interactions should be just a couple of seconds. And taking action should be just as fast. Simple actions that only require a single decision work best on Apple Watch. People should be able to set a timer, or turn on an alarm, or check things off on their Reminders List in 2 seconds or less.

Now even if you can't quite get interaction times down to 2 seconds, the act of trying to do so will help you spot workflow inefficiencies and find ways to streamline your app. All right, so now let's get down into the details of how to make really great apps, notifications, and complications. Now, in my humble opinion, complications are the easiest and most glanceable interaction that someone can have on Apple Watch.

Checking a complication is as easy as raising one's wrist and looking. No additional interaction is required. This is definitely an interaction that takes 2 seconds or less. And with watchOS 3 and iOS 10, big changes were made to raise awareness about complications to make them easier to install and to give them added capabilities.

So, for starters, you can now use Apple Watch app on iOS to browse and configure complications, which makes a lot of sense because this is definitely an interaction which takes more than 2 seconds. Now the configuration UI shows an accurate preview of how the complication will look on the watch face, and it's easy for people to see what your complication does and the value it will provide to them.

The Apple Watch app also has a gallery of watch faces that are preconfigured with complications. And there's a section dedicated to third-party complications. Now if you've made a complication bundle, Apple Watch owners who have your iOS app already installed will see your complication here. If your complication looks useful, people can simply tap to install it. And this will install your watch app in the background. The feature complication is a really great way to raise awareness about your watch apps. It will now be so much easier for people to learn about the complications that you make.

Now another big change has to do with performance. Any app with a complication on the user's current watch face will be kept in memory and have more background update opportunities. This means that launch time is going to be way faster and app data should be less stale. Complications are great app launchers, and the information that they display often motivates people to want to know more. So that process has to be quick. So seeing the current temperature might make you curious about this week's forecast.

Or, seeing that your primary stock might be doing well could make you want to know how the overall market is doing. And the last big change to complications relates to the frequency of updates. In watchOS 3, your app has opportunity to update your complication 50 times in a day.

You control the frequency and timing of these updates. So a travel complication could update most frequently around the departure and arrival time of a flight, while a sport complication might update most frequently around a game that you're following. By controlling when updates occur, your complication can stay current when it matters most.

Now as you work on your complication, consider how external factors and user activity patterns might affect the timing of your complication updates. So, if you're going to build an Apple Watch app, you should make a complication. There's a reason why they became so popular among watch owners and watchmakers.

All of that complexity was worth the effort. So I hope I've done a decent job at least of selling you on the idea of making a complication. And if so, I'd like to talk to you a little bit about what it takes to make a really great complication.

Now the most important consideration when designing a complication is just choosing what information to display. The best complications answer those questions that people tend to ask themselves throughout their day. Now I run most days before I go to work. So the night before, I might check to see what time the sun will rise before setting my alarm clock. And when I get up, I want to know what the temperature is outside so I know how to dress for my run.

And I'll check to see what time my first meeting is to make sure I have enough time to run. And I'll also check to see the traffic to make sure I don't need to leave really early to get to work. Now the answers to these questions will directly impact how I plan my day. And by answering these questions for me with a simple raise of the wrist, these complications provide real and immediate value throughout my day. And complications can be a really powerful motivator. They can inspire you to take action. More actionable.

The Activity complication, for example, shows me progress towards my fitness goals throughout the day. I can see if I'm on track to filling those rings, or if I need to go for an extra-long walk with my dogs after work. And WaterMinder's complication shows how much progress I'm making towards my daily hydration goal. And it seems I'm actually a little bit behind, so I'm going to take this as an opportunity to drink some water. Hold on one second. Ahh.

So, if you had to pick just one thing to communicate with your complication to the people that use your app, what would that be? What's the thing that they're most interested in knowing throughout the course of their day? Does that information change frequently enough to remain interesting? Now, sometimes, the answer to that question is not so clear.

Now if you can't quite narrow it down to just one piece of information, consider giving people options. That's what the app CARROT Weather does. They let you configure what type of weather information you want to see. Temperature, temperature and condition, wind, UV index, precipitation, chance of precipitation, or humidity. Now during the summertime in California, it hardly ever rains. So seeing the chance of precipitation is completely irrelevant. 0% today. That is completely shocking. Of course, just as an aside, I saw the weather this morning. It's actually supposed to rain tomorrow. So, heads up.

Just in time. But, you know, during the same period of time in the summer, the UV index is incredibly relevant information. And allowing this complication to be customizable is a really great feature. And CARROT Weather has also done a great job of making their complication glanceable. Each one, except for just current temperature, uses a simple and meaningful icon to label the value that's shown.

And they don't try to cram in too much information either because that would just lead to text and icons that are too small to read. Now if you haven't made a complication before, it's important to know that there are multiple complication families. Circular, modular small, modular large, utility small, and utility large. And new to watchOS 3, extra-large.

I wanted to get a sound effect for that, but I didn't have time. Now each of these complication families consist of one or more complication templates and corresponds to particular watch faces. The Color watch face uses the circular complication family. The modular watch face uses the modular large complication family and the modular small family. The simple utility and chronograph watch faces use utility small complications. And the utility and Mickey watch faces use the utility large complication family.

And the all-new extra-large watch face uses, does anyone want to guess? That's right. Extra-large watch face uses the extra-large complication family. You guys are quick. Now I hope you wrote all that down because that information will never be shared again. No, I'm just kidding. All of that information is available to you in the watchOS Human Interface Guidelines. This is your go-to place for all information related to the design of your watch app. I highly recommend checking it out.

Now it's important that you try to make something for every complication family so that people can use your complication on the watch face that they like best. And be sure to use placeholder data for your complication that's representative of what people will see when they actually use your complication. Without placeholder data, it's going to be impossible for people to anticipate what your complication will do.

All right. As you can see, some complications offer more room for more detailed information. On the modular watch face, if someone has made your complication the centerpiece, they certainly care a lot about what your app has to tell them. Take this as an opportunity to provide slightly more information that they might find helpful. In fact, you may want to display totally different information based on the complication family. If weather information is really important to you, there's no reason why you couldn't have two instances of the CARROT Weather complication on your watch face.

Maybe you'd use modular large to show current temperature and condition, and modular small to show chance of precipitation. Now even if you can't quite figure out what information to show in your complication, you can always just make an app launcher. The complication for Just Press Record, which is an app for recording voice memos, is just an app launcher.

Tapping it launches the app of course, but it also begins a new recording. It's super convenient and fast. So if it's not already clear, we like complications, like, a lot. And we think that Apple Watch owners -- the more Apple Watch owners learn about how useful complications are, the more complications they'll want to have.

Now to make it easier to access all of those complications, people can now easily switch watch faces on watchOS 3. With a simple swipe, you can go from your workday complication to the workout watch face, and from the workout watch face to the weekend watch face. Now think about all of the different things that we do with our time. Right? The variety is staggering.

No, seriously. We workout, we hangout, we exercise, we travel, we play sports and do countless other types of activities. Now, it'll be easier to match the watch face and complications installed to what it is that you're doing. And this should lead to people using a wider number of complications on Apple Watch. Make one of those complications yours. All right, so that was complications. Now, let's move on to best practices for notifications.

Notifications should always be useful and timely, and they should be carefully designed to communicate information with precision and clarity. In other words, they should be glanceable. Keep in mind that the person receiving your notification could be anywhere and doing just about anything. They could be at dinner, hanging out with friends, riding on the subway, getting hydrated, or in a meeting discussing something of real importance. Now, in so many situations, people are fully engaged in the task at hand or just really paying attention to the world around them. So your notifications need to communicate clearly and get to the point.

Luckily, making your notification glanceable is not so difficult. First, you just need to provide a meaningful title. Now notifications come in two stages, ashort look and a long look. And as the name implies, the short look is there to give you a sense of what the notification is about really quickly. And the title that you provide will get displayed here. Now, in some cases, that title might tell you everything you need to know about the notification.

Second, only show what's necessary. I can't stress this enough. The more you show in a notification, the harder it's going to be for people to focus on what's most important. So let's say you're making a check-in notification for a travel app. The notification might contain all sorts of potentially useful information about the traveler's flight. But seeing things like the flight number or your own name in a notification when it's just really implied is not all that important, so we can just remove that information altogether.

Third, present important information first. By putting the most important things at the top, people are more likely to get the message quickly without the need to scroll. And this is really helpful if someone is carrying stuff around and they might not be able to easily swipe the screen or access the Digital Crown. So for our check-in notification, we might move content like the flight number and boarding time a little bit further down in the notification.

Fourth, vary the size and appearance of type to establish a clear visual hierarchy. Your notification should focus people's attention on the most important information first. This notification has all the right information and it's in the right order, but everything here is treated with equivalent visual weight. Apple Watch notifications are very customizable.

You have full control over font appearance, layout, background and sash color. Use this capability to help people quickly pick out what's most important. Now this design really puts the focus on things like ticket class, seat number, departure time, and route. And the purpose of this notification that it's time for you to check in now, is made very clear.

And lastly, thoughtfully-designed notifications often use icons, graphics, and animations to convey meaning quickly and with impact. Visuals can sometimes communicate meaning faster and more clearly than text. Icons can help save space and allow your notification to display everything on screen at once. But be mindful that some icons may not be universally understood or could be misinterpreted.

So you want to look for icons that are widely understood across regions and cultures, or whose symbolism you know to be clear to the people who use your app. And short, meaningful animations can be a great way to complement text and to engage people's attention. And graphs and other data visualizations not only provide for a more interesting visual experience, but may pack in far more meaning than text alone. But there's more to consider when it comes to the design of your notifications.

You also need to think carefully about why and when you're sending them. Getting a notification at the wrong time can be just distracting or really annoying. If you got a notification right now, you would be so annoyed unless it was about something even more important than being here right now, which is completely ridiculous [laughter].

Now, because Apple Watch effectively taps people on their wrist when they receive a notification, notifications are very hard to miss. If your app sends people notifications that are not genuinely useful, informative, and timely, people are likely to just turn off your app's ability to send notifications altogether. So, how do you know why and when to send notifications?

Well, the best approach is to determine what's most relevant to the people who use your app and intelligently time notifications for when they're most actionable. Now I have two really great apps that -- I have two really great examples of this. The first is from the awesome weather app, Dark Sky.

Dark Sky notifies people about significant weather condition changes, such as when it's about to start raining or when rain is about to stop. Now, in the case of Dark Sky, relevance is determined by contextual factors. Notifications are sent based on the user's location or proximity to an approaching or departing weather system.

And notifications are sent early enough so that there's time to get the umbrella out before it starts pouring down raining cats and dogs. Now, because these notifications are contextually relevant and timely, they are more actionable. Knowing that it's about to stop raining might motivate me to get ready to go for a run.

Knowing that it's about to start raining might motivate me to walk to my couch and take a nap. Now, in addition to contextual factors, user preferences and patterns can provide really great insights into what people want to know and when they want to know about it. Now, to explain, let's look at the other example.

Streaks is an app that helps people form positive habits and also just won an Apple Design Award. People can pick up to six tasks that they want to do on a daily basis. Now, as the name suggests, the objective here is to go on streaks of daily tasks because doing something every day helps it to become a routine.

So, if you want to get into the habit of doing core-strengthening exercises every day. Which I should be doing or learning how to play guitar, or remembering to refill your dog's water bowl or take him for a walk, Streaks is going to help you remember to do it. My dogs have never been so fit and hydrated. They don't realize it, but they totally love this app. Of course, the whole point here is that these are things that people want to do on a regular basis but just can't seem to remember to do it.

So Streaks uses notifications to keep people on track. But these reminders are only effective if they come at just the right time. They should arrive close to when people are most likely to take action. Or, put another way, when they're most actionable. But how does Streaks know when that is?

Well, at first, they don't. To explain what it does, let's look at a specific example. Now I'm trying to get into the habit of playing guitar. And at a somewhat randomized time towards the end of the day, I'll get a reminder to play guitar. It doesn't arrive so late that I might not have time to play guitar or that I'm already asleep. But it's not so early that I'm, say, still at work.

So, for simplicity's sake, let's say I get the notification at 7:00 PM. Now, that's a bit early. So I can tap a 30-minute snooze button and keep delaying and delaying that notification until I'm finally able to play guitar. And when I play guitar, I mark that task as complete in the app.

Streaks takes note of this time. Day after day, each time I mark that task as complete, Streaks gets an increasingly more accurate understanding of when I typically play guitar. Streaks uses that time to schedule my reminders to automatically arrive at just the right moments. It's such a simple and elegant heuristic.

The actual timing is 30 minutes prior because obviously I can't just drop everything at the drop of a hat and start playing guitar. However, automatically adjusting the timing and notifications might not always be the right choice. Some tasks you want to do at very specific times, and Streaks gives you that capability as well.

Or maybe you don't want individual notifications, you just want one single daily reminder. So Streaks gives you that choice. And you can disable individual task notifications or turn off notifications altogether. So by smartly choosing when notifications are scheduled, and giving users full control over why and when they like to be notified, the reminders that Streaks sends are less likely to be disruptive, ignored, and unwelcome.

Now the notifications that Streaks sends are actionable insofar as they remind people to perform what's typically a physical task. But making notifications actionable also means quite literally adding actions to your notifications. Now I encourage you to explore how to make the notifications that you send actionable. Being able to quickly triage from your wrist is a very powerful thing.

Notifications can push interactions to the people who use your app, and they're great for offering brief periods of engagement to people throughout the course of their day. Now you can have up to four actions in a notification. And be sure to only show actions that are truly relevant to the content of your notification.

Make sure that actions are labeled clearly, succinctly, and use action-oriented verbs. And try to focus on actions that can be completed in one tap just one tap and you're done. However, sometimes one or two additional steps might be required. Now multi-step flows will bring people into your app, and that used to be a little bit painful because apps would take a little bit of time to load.

But in watchOS 3, when your app's notification is displayed, your app will be launched in the background. This gives you an opportunity to make sure your app's data is current and get your app ready for people to show up. So don't shy away from taking people into your app if that's what's necessary. Now, speaking of taking people into your app, it's time to talk about apps.

watchOS 3 will profoundly change how people experience and interact with apps. Let's take a look at the most significant changes and what they'll mean to you. Let's start with the new Dock. People can put up to 10 of their favorite apps into the Dock, and every app in the Dock is kept in memory to make getting from the Dock into an app fast. And what's shown are snapshots from each app. These snapshots should be designed to be informative and glanceable. And snapshots from your app can be regularly updated to keep them current.

Apps in the Dock are launched in the background at least once an hour. This lets you fetch new data, update your app's UI, and request that the system takes a new snapshot of your app if it's necessary. And when your app is viewed in the Dock, it'll be woken up so that it can update its snapshot if content is changed.

Now when someone puts your app in the Dock, you should be flattered. Being in the Dock means that your app contains information that people want to be regularly updated about. Because of this, it's important that the snapshots of your app are not only current but also relevant. Now, in some situations, showing people the last screen that they saw when they were using your app might not be that relevant.

Fortunately, watchOS 3 provides an API for navigating people to a different screen than the one that they were last looking at. So, for instance, imagine a baseball app that shows a list view of current and upcoming games. And of course, each of these is tapable so that you can go to a detail screen about those games.

Okay. Now, imagine yourself as a user of this app. The last time you were in the app, you were looking at this particular game. And when you exit out and look at the app in the Dock, you probably expect to continue to see the details about that game.

And when the game ends, go Giants. You probably still expect to see this game in the detail view. But after a little while, the details about this particular game become less and less relevant. You may have learned about the final score from a notification the app sends, or from a friend, on Twitter, in the news.

At some point, the content here becomes completely irrelevant. You're not interested in that game at all. Perhaps you're going to be more interested in seeing the next day's schedule. Or if your favorite team is playing a new game that's already started, wouldn't you want to see the details about that game? Now these are the sorts of questions that you need to be asking about your app. And as you do so, I want you to consider the following best practices.

First and foremost, your objective is to proactively anticipate user interests and needs. Put yourself in their place and think it through. Graphing events onto a timeline is a very helpful technique for doing this. Plot out significant events in time and then ask yourself, "How do these events influence what people would want to know?" In the hypothetical baseball app example I just went through, I speculated that people will want to see game details around or during the times where games are being played. While, at other times, those same people might want to know about the overall league schedule.

However, this is probably a gross oversimplification. Individual preferences can have a big impact on what's most relevant to people. For instance, a fair-weather fan who only cares about one team might expect to see something totally different than a hardcore baseball fanatic who wants to follow every game. And for other apps, other contextual factors like time of day and location can have a huge impact on what people want to see.

Now, as a general rule, people don't always love it when an app changes in unpredictable ways and the state isn't saved. And it can be confusing or disorienting. So if you choose to navigate people to a different view, you want to do so in a way that's logical and predictable. The hope is that people won't even stop to realize what's going on. But if they do, they should be able to make some really accurate guesses about why the state of your app's UI changes from time to time.

And I would also recommend against making the snapshot look radically different from your app. This can make your app a little bit less recognizable, and may be harder to find. Now it's totally fine to just focus on some information or maybe hide some stuff that isn't as relevant when your app is shown in the Dock. But, you know, if you want to exaggerate the size of certain things for legibility that might be fine. But don't make it look completely different.

Now next, avoid showing things like alerts, or confirmation dialogues, or error states in your snapshot. When seen out of context, these sorts of screens may not be very helpful. And in fact, they might be easily misinterpreted or make no sense at all. So, depending on the situation, consider programmatically dismissing these screens after some period of time.

And lastly, optimize your app interface for being displayed in a miniaturized form. Now, in the Dock, apps get scaled down to -- and this is, like, just a ballpark rough figure but 62.4851% of their full size UI. You'll want to avoid text and graphics from becoming illegible at this small size. Now for this very reason, the font weight for status bars and a lot of text in the built-in apps was increased from regular to medium. At smaller sizes, bolder fonts are more legible.

And for really key information, try using large format type. This may require removing some stuff out of your interface to make space, but that's not such a bad thing to do anyway. Now, by following these guidelines, your apps will be as glanceable as possible in the Dock. And speaking of glanceable, some of you may be wondering about Glances.

Glances were designed to be a browsable collection of timely and contextually-relevant moments from the user's favorite apps. Not coincidentally, the Dock serves essentially the same purpose while simplifying the overall platform experience. In a way, Glances evolved into the Dock. And the Dock, in turn, made Glances kind of redundant. So they were removed from watchOS. With that said, the time and thought that you may have put into designing your Glances is totally applicable to thinking about how to design your app to look great in the Dock.

Okay. So, the next big change to apps on watchOS 3 is a simple but powerful improvement to how people navigate within apps. Most existing Apple Watch apps are structured hierarchically. Basically, a top-level list and a bunch of detail screens. Now that's not so surprising because we tend to organize data hierarchically. Unfortunately, navigating between those screens can be inefficient as you have to return to that top-level view every single time.

So, for example, if I want to get to those detail views, I select an item, drill in, go back, select another item, drill in, go back. So forth and so on. It's kind of like being in a room in a house and you want to get to the room right next to you. But in order to get there, you have to go up a flight of stairs and then back down another flight of stairs.

It'd be so much more efficient if there was just a door to take you there. So in watchOS 3, we now have doors, I guess. It's now possible to navigate directly from one detail view to another by swiping vertically or using the Digital Crown. Think of it like vertical paging from one detail to the next.

Now if your app is already structured hierarchically, you should really consider enabling this feature. But one thing to point out is that this behavior will only work when the detail screens are not taller than the display. So with the previous version of Weather, the 10-day forecast made the screen a lot taller. It was accessed by scrolling down from today's forecast. In the new version of Weather, that information was pushed to a child view so that everything could fit on screen at once.

So if you want to opt into this behavior, you may have to refactor your design to make everything fit. And for those of you with a page-based app, now is a really good time to switch to hierarchy or to consider doing so. Navigating with the Digital Crown is far more efficient than swiping horizontally from one page to another.

And page-based apps do not support hierarchy. Obviously, that's not a limitation here. And having a top-level list view of a lot of detail items can be really useful. By moving from a page-based structure to a hierarchical one, our Weather App can show the current high and low temperatures for multiple cities at once. This is very handy.

Okay. Now, the third big change for apps on watchOS 3 relates to stickiness. Now besides just being a lot of fun to say, stickiness describes how long an app will remain in the foreground. On watchOS 3, apps can stick around for 8 minutes, which is quite a bit longer than before. So when someone is using your Watch app and then drops their wrist, your app will be the first thing they see when they raise their wrist again as long as they do so within 8 minutes.

In fact, with every raise of the wrist, that timer gets reset back to 8 minutes. Now making apps stickier is a really significant change. Apple Watch apps are intended to compliment activities that can occur over many minutes of time, or even hours. But during those periods, the Watch display can be asleep for many minutes at a time.

So, one example might be a grocery list app. When shopping, most of your time is spent checking prices, reading labels, inspecting produce, trying to avoid crashing into other shopping carts, and trying to look cool. There are so many activities that are just like this. They're what we might call sessions or session-based activities. Cooking dinner, playing sports, working out, getting directions. These things all take extended periods of time in which people will periodically check their watch to stay on task. Stronger stickiness puts you immediately back into the app where you left off, which saves a lot of time.

Okay. Now, the fourth major watchOS change for apps involves letting people know when it's okay to drop their wrist. When people initiate a task in your app, they expect to get confirmation feedback. Did the task succeed or did it fail? Unfortunately, providing definitive success of failure, conformation of success or failure can take a while. Slow networks, weak Wi-Fi signal, and long Bluetooth ranges might create communication delays or remote delays.

Apps that allow people to control physical devices, like garage doors or window blinds, might be unable to provide completion feedback until those devices have fully opened or closed. And some services such as food delivery or ride-ordering apps may involve communication with other people. And as we all know, people do not always get back to you promptly.

Now on an iPhone or a Mac, you would ordinarily keep people engaged with your app while you're trying to get them that confirmation feedback. Progress indicators are a way to hold people's attention. They make people anticipate feedback. They basically say, "Hold on a second. I'll be right with you." But, however, it might be more than a second. All the while, the person who's using your app has their wrist raised. Their shoulder starts to get a little tired. Seconds start to feel like minutes. It really starts to slow down.

So, to avoid this situation on Apple Watch, you should use an NSURL background download task to communicate with your server. This does two things. First, it helps to make sure that you can communicate to your server before your app gets suspended. And second, when your server responds, Apple Watch will wake up your app. And then, in turn, you can quickly run in the background and do something like send a local notification, which is also new to watchOS 3, to provide feedback to the person who's using your app. So, for example, say you're working on a food-ordering app.

When someone places a food order, your app needs to make sure that the restaurant can fulfill the order and provide an estimated delivery time. You wouldn't want people to keep waiting while your app figures these things out. Instead, it's way better to provide immediate feedback that their order has been sent to the restaurant. You can also let people know, you also should let people know. That once the restaurant accepts the order and provides an estimated delivery time, you'll send a final confirmation to them that the order has been processed and is on its way.

Now, if you've done this right, people should feel free to drop their wrist, trusting that your app is working hard to complete the task that you've assigned to it. And if all goes well, you send a local notification to people to let them know that the order was successfully placed and it is on its way.

And if there's a problem, clearly state what went wrong and help people address the issue with minimal additional interaction. Now, the key to making all of this work is trust. People need to trust that your app works, that it won't crash, and that you'll make sure that they stay informed about whether the task succeeded or failed. And related to trust, you never want to mislead people into thinking that a task is fully complete if it's actually still in progress. That's basically lying, which is not good for building trust.

Okay, so that was a lot of new stuff about apps. And there's still a little bit more to cover, but I just wanted to pause here for a second and take stock. We looked at the new Dock UI and how to make your app as glanceable and responsive as possible.

We saw how the Digital Crown will make navigating between detail screens and hierarchical apps way more efficient. We learned how session-based apps will benefit from changes to app stickiness. And we just saw how the ability to schedule local notifications while your app runs in the background can give the people who use your app the confidence to drop their wrist to keep interactions quick. Now we think that these improvements to watchOS will empower you to create streamline user flows that shorten user interaction times.

Now, if the Apple Watch team had stopped there, this would have been a really significant release. I would have had plenty to talk to you about today. But they did not stop there. They're like a bunch of overachievers. The kind of people who made me look really bad in high school.

In watchOS 3, there's some really cool new APIs and frameworks to let you do some amazing things. For starters, watchOS 3 now has SpriteKit and SceneKit, our 2D and 3D graphics frameworks. SpriteKit and SceneKit let you render and animate graphics. They let you make elements respond to gestures, or to animate things programmatically.

And you can implement physics facts. I mean, it's crazy. Force fields, detect collisions, and more. Now you might think about these things as being technologies for games, but you can use them in apps as well. And watchOS 3 has gesture support. Up until now, touch input was handled indirectly.

The controls and views that you had in your app would respond to touch events on your behalf. Now, you have the ability to do something totally custom. So you can do something custom with tap, or swipe, or pan, or long press. This one takes a little bit of time.

Okay, in watchOS 3, you now have access to raw Digital Crown events. You can use this data to alter the color, dimensions, and other visual properties of UI elements. Or, you can use the Digital Crown for changing selection or modifying values. So, what can you do with all of these capabilities? Well, for starters, many of you have wanted to visualize data using a ring or an arc. With SpriteKit, you can draw an element like this programmatically so that you can easily animate between any two arbitrary values.

You can use the default ease-in curve which provides a really nice ease in and ease out. Or, you can do something custom with ease-in curves for a bouncy animation, or really any kind of animation that you'd like. There's a ton of open source ease-in curves made by the very generous people in the SpriteKit developer community. And you can even do things like modify the fill color of the rings to reflect the current value.

Data visualization, like charts and graphs, can really come to life with animation. By drawing this chart programmatically, we can animate the built-in to add visual interest, or we can use animation to draw people's attention to a particular part of the chart. SpriteKit properties are mutable, so you can easily repurpose one chart to display different properties based on user input.

Or, perhaps you want to let people inspect different values along the graph with a pan gesture. Totally. Or, better still, you can let people use the Digital Crown to do the same thing. Or, let people zoom into the chart. Or, maybe let people scroll. And since you have full control over the Digital Crown and how the graph responds, you can control how fast or slowly things happen in response to rotation.

Now, I could go on. This is a lot of fun to just try to think about this stuff, but that would take all of the fun out of it for you. Now, I encourage you to learn more about SpriteKit and SceneKit, and experiment with using these technologies to create richer and more meaningful experiences. But just remember, with increased freedom comes increased responsibility.

Animating something just because it looks cool is really not a good reason. When used well, animation helps communicate meaning more quickly, and thereby shortens interaction times. Similarly, making a graph interactive should provide a richer and more informative user experience, and ideally reduce the need for more complicated or dense UIs.

Okay. So, we've covered a lot of ground today, but I did want to leave you with one final thought about designing your watch app. Making a great Apple Watch experience requires keeping things simple. But making something simple is not so simple to do. And bonus points if you know where this is from. Keeping things simple involves making hard choices about what your app will do. It means saying no to a lot of really interesting-sounding ideas. But just because you can do something does not mean that you should.

Keeping things simple also means thinking deeply about the journey that people take throughout the course of their day. People will experience your app over time. And the way that you design your app should be a reflection of this. Think less in terms of static screens and more in terms of user flows.

Account for the fact that these flows are not continuous, uninterrupted experiences. People will drop in at arbitrary times throughout the day. And when they do, they'll always expect your app to be current and relevant to their constantly-shifting needs. Your app should anticipate what people want to do at any given moment, and attempt to proactively offer information and functionality that's contextually relevant and timely. Now doing that right is not so simple.

Designing for Apple Watch is different than designing for an iPhone, an iPad, Apple TV, or Mac. What we know about designing and building apps for these devices has shaped our notions about how complex apps should be, how people navigate them, and how much time they're willing to engage with your app. Try to recognize and challenge your own deeply-rooted assumptions. This is easier said than done. I know. But this is a crucial step towards making a really great watch app.

Now, for Apple Watch, perhaps the best advice that I can offer you is to think in terms of features and not apps. Making something great for Apple Watch may involve offering just one feature. Just Press Record is essentially just one feature. The complication is the Record button, and the app is the recording interface and Stop button. It works great. And I literally just described the app in one sentence.

Two seconds goes by in a flash. There's nothing simple about designing for such brief interactions. But I hope the concepts and techniques that we discussed today will empower you to do just that. And I'm really excited to see what you can do with all of the new capabilities in watchOS 3. A lot of people worked hard on this release, and all of that work was in the service of helping you to build more innovative, delightful, and platform-defining experiences.

Okay. So for more information about what we covered today, please check out the video page where there's a ton of extra resources. Again, definitely go and check out the watchOS Human Interface Guidelines. There's a ton of really great resources there. And we're going to continue updating this over the summer, so check in regularly.

We also have a lot of great Watch engineering sessions. I would definitely recommend going and checking out SpriteKit one and watching some of the videos of the ones that have already happened. And this year, we had a lot of really good design sessions. Some of them are still to come.

I highly recommend Inclusive App Design, which will help you to design for accessibility and to be really great for people around the world. I also recommend the video this morning about Typography and Fonts. And there's one more design session about Iterative UI Designs that you can take your ideas and refine them and come up with something that's really awesome. With that, thank you very much for your time.