Designing For Android

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For designers, Android is the elephant in the room when it comes to app design. As much as designers would like to think it’s an iOS1 world in which all anyones cares about are iPhones, iPads and the App Store, nobody can ignore that Android currently has the majority of smartphone market share2 and that it is being used on everything from tablets to e-readers3. In short, the Google Android platform is quickly becoming ubiquitous, and brands are starting to notice.

But let’s face it. Android’s multiple devices and form factors make it feel like designing for it is an uphill battle. And its cryptic documentation4 is hardly a starting point for designing and producing great apps. Surf the Web for resources on Android design and you’ll find little there to guide you.

If all this feels discouraging (and if it’s the reason you’re not designing apps for Android), you’re not alone. Fortunately, Android is beginning to address the issues with multiple devices and screen sizes, and device makers are slowly arriving at standards that will eventually reduce complexity.

This article will help designers become familiar with what they need to know to get started with Android and to deliver the right assets to the development team. The topics we’ll cover are:

  • Demystifying Android screen densities,
  • Learning the fundamentals of Android design via design patterns,
  • Design assets your developer needs,
  • How to get screenshots,
  • What Android 3 is about, and what’s on the horizon.

Android Smartphones And Display Sizes

When starting any digital design project, understanding the hardware first is a good idea. For iOS apps, that would be the iPhone and iPod Touch. Android, meanwhile, spans dozens of devices and makers. Where to begin?

The old baseline for screens supported for Android smartphone devices was the T-Mobile G1, the first commercially available Android-powered device which has an HVGA screen measuring 320 x 480 pixels.

HVGA5 stands for “half-size video graphics array” (or half-size VGA) and is the standard display size for today’s smartphones. The iPhone 3GS, 3G and 2G use the same configuration.

Screenshot6
T-Mobile G1, the first commercially available Android device and the baseline for Android screen specifications.

To keep things simple, Android breaks down physical screen sizes (measured as the screen’s diagonal length from the top-left corner to bottom-right corner) into four general sizes: small, normal, large and xlarge.

Screenshot7
Two common Android screen sizes. (Image from Google I/O 2010)

320 × 480 is considered a “normal” screen size by Android. As for “xlarge,” think tablets. However, the most popular Android smartphones8 today have WVGA (i.e. wide VGA) 800+ × 480-pixel HD displays. So, what’s “normal” is quickly changing. For now, we’ll say that most Android smartphones have large screens.

Screenshot9
Diagram of various screen configurations available from emulator skins in the Android SDK. (Image: Android Developers website)

The variety of display sizes can be challenging for designers who are trying to create one-size-fits-all layouts. I’ve found the best approach is to design one set of layouts for 320 x 533 physical pixels and then introduce custom layouts for the other screen sizes.

While this creates more work for both the designer and developer, the larger physical screen size on bigger devices such as the Motorola Droid and HTC Evo might require changes to the baseline layouts that make better use of the extra real estate.

What You Need to Know About Screen Densities

Screen sizes are only half the picture! Developers don’t refer to a screen’s resolution, but rather its density. Here’s how Android defines the terms in its Developers Guide10:

  • Resolution
    The total number of physical pixels on a screen.
  • Screen density
    The quantity of pixels within a physical area of the screen, usually referred to as DPI (dots per inch).
  • Density-independent pixel (DP)
    This is a virtual pixel unit that you would use when defining a layout’s UI in order to express the layout’s dimensions or position in a density-independent way. The density-independent pixel is equivalent to one physical pixel on a 160 DPI screen, which is the baseline density assumed by the system of a “medium”-density screen. At runtime, the system transparently handles any scaling of the DP units as necessary, based on the actual density of the screen in use. The conversion of DP units to screen pixels is simple: pixels = DP * (DPI / 160). For example, on a 240 DPI screen, 1 DP equals 1.5 physical pixels. Always use DP units when defining your application’s UI to ensure that the UI displays properly on screens with different densities.

It’s a bit confusing, but this is what you need to know: Like screen sizes, Android divides screen densities into four basic densities: ldpi (low), mdpi (medium), hdpi (high), and xhdpi (extra high). This is important because you’ll need to deliver all graphical assets (bitmaps) in sets of different densities. At the very least, you’ll need to deliver mdpi and hdpi sets for any smartphone apps.

What this means is all bitmap graphics need to be scaled up or down from your baseline (320 x 533) screen layouts (note: there is also a way for parsing SVG files11 that provides a way to scale vector art on different screens sizes and densities without loss of image quality).

The bitmap requirement is similar to preparing graphics for print vs. the Web. If you have any experience with print production, you’ll know that a 72 PPI image will look very pixelated and blurry when scaled up and printed. Instead, you would need to redo the image as a vector image or use a high-resolution photo and then set the file’s resolution at around 300 PPI in order to print it without any loss of image quality. Screen density for Android works similar, except that we’re not changing the file’s resolution, only the image’s size (i.e. standard 72 PPI is fine).

Let’s say you took a bitmap icon measuring 100 × 100 pixels from one of the screens of your baseline designs (remember the “baseline” is a layout set at 320 × 480). Placing this same 100 × 100 icon on a device with an lDPI screen would make the icon appear big and blurry. Likewise, placing it on a device with an hDPI screen would make it appear too small (due to the device having more dots per inch than the mDPI screen).

Screenshot12
An application without density support. (Image: Android Developers website)

To adjust for the different device screen densities, we need to follow a 3:4:6:8 scaling ratio between the four density sizes. (For the iPhone, it’s easy: it’s just a 2:1 ratio between the iPhone 4 and 3GS.) Using our ratios and some simple math, we can create four different versions of our bitmap to hand off to our developer for production:

  • 75 × 75 for low-density screens (i.e. ×0.75);
  • 100 × 100 for medium-density screens (our baseline);
  • 150 × 150 for high-density screens (×1.5);
  • 200 × 200 for extra high-density screens (×2.0). (We’re concerned with only lDPI, mDPI and hDPI for Android smartphone apps.)

Screenshot13
The final graphic assets would appear like this using the four different screen densities.

After you’ve produced all of your graphics, you could organize your graphics library as follows:

Screenshot14
The suggested organization and labeling of asset folders and files. In preparing our star graphic, all file prefixes could be preceded by the name ic_star, without changing the names of the respective densities.

You might be confused about what PPI (pixels per inch) to set your deliverables at. Just leave them at the standard 72 PPI, and scale the images accordingly.

Using Android Design Patterns

Clients often ask whether they can use their iPhone app design for Android. If you’re looking for shortcuts, building an app for mobile Web browsers using something like Webkit15 and HTML5 is perhaps a better choice. But to produce a native Android app, the answer is no. Why? Because Android’s UI conventions are different from iPhone’s.

The big difference is the “Back” key, for navigating to previous pages. The Back key on Android devices is fixed and always available to the user, regardless of the app. It’s either a physical part of the device or digitally fixed to the bottom of the screen, independent of any app, as in the recently released Android 3.0 for tablets (more on this later).

Screenshot16
The hard “Back” key on a smartphone running Android 2.0.

The presence of a Back key outside of the app itself leaves space for other elements at the top of the screen, such as a logo, title or menu. While this navigational convention differs greatly from that of iOS, there are still other differentiators that Android calls “design patterns.” According to Android, a design pattern is a “general solution to a recurring problem.” Below are the main Android design patterns that were introduced with version 2.0.

Dashboard

This pattern solves the problem of having to navigate to several layers within an app. It provides a launch pad solution for rich apps such as Facebook, LinkedIn and Evernote.

Screenshot17
The dashboard design pattern, as used by Facebook and LinkedIn.

Action Bar

The action bar is one of Android’s most important design patterns and differentiators. It works very similar to a conventional website’s banner, with the logo or title typically on the left and the navigation items on the right. The action bar’s design is flexible and allows for hovering menus and expanding search boxes. It’s generally used as a global feature rather than a contextual one.

Screenshot18
The action bar design pattern as used by Twitter.

Search Bar

This gives the user a simple way to search by category, and it provides search suggestions.

Screenshot19
The search bar design pattern as used in the Google Search app.

Quick Actions

This design pattern is similar to iOS’ pop-up behavior that gives the user additional contextual actions. For example, tapping a photo in an app might trigger a quick action bar that allows the user to share the photo.

Screenshot20
The quick action design pattern as used by Twitter.

Companion Widget

Widgets21 allow an app to display notifications on the user’s launch screen. Unlike push notifications in iOS, which behave as temporary modal dialogs, companion widgets remain on the launch screen. (Tip: to select a widget for your Android device, simply tap and hold any empty space on one of the launch screens.)

Screenshot22
Companion widgets by Engadget, New York Times and Pandora.

Using established design patterns is important for keeping the experience intuitive and familiar for your users. Users don’t want an iPhone experience on their Android device any more than a Mac user wants a Microsoft experience in their Mac OS environment. Understanding design patterns is the first step to learning to speak Android and designing an optimal experience for its users. Your developers will also thank you!

Android Design Deliverables

OK, so you’ve designed your Android app and are ready to make it a reality. What do you need to hand off to the developer? Here’s a quick list of deliverables:

  1. Annotated wireframes of the user experience based on the baseline large screen size of 320 x 533 physical pixels. Include any additional screens for instances where a larger or smaller (320 x 480) screen size requires a modified layout or a landscape version is required.
  2. Visual design mockups of key screens for WVGA large size (320 x 533) screens (based on a WVGA 800 x 480 hdpi physical pixel screen size) in addition to any custom layouts needed for other screen sizes.
  3. Specifications for spacing, font23 sizes and colors, and an indication of any bitmaps.
  4. A graphics library with lDPI, mDPI and hDPI versions of all bitmaps saved as transparent PNG files.
  5. Density-specific app icons, including the app’s launch icon, as transparent PNG files. Android already provides excellent tips for designers24 on this topic, along with some downloads, including graphic PSD templates and other goodies25.

How To Take Screenshots

Your product manager has just asked for screenshots of the developer’s build. The developer is busy and can’t get them to you until tomorrow. What do you do?! As of this writing, Android has no built-in way to take screenshots (bummer, I know). The only way is to just deal with it, and that means pretending to be a developer for a while and downloading some really scary software. Let’s get started!

The following software must be downloaded:

  1. All USB drivers for your Android device,
  2. Android software development kit26 (SDK),
  3. Java SE SDK27

Then, on your computer:

  1. Extract the USB drivers to a folder on your desktop,
  2. Extract the Android SDK to a folder on your desktop,
  3. Install the Java SE SDK.

On your Android device:

  1. Open “Settings” (you’ll find it in the apps menu),
  2. Tap on “Applications,”
  3. Tap on “Development,”
  4. Check the box for “USB debugging.”

Screenshot28

Now, for the fun part:

  1. Connect your Android device to your computer via USB. Windows users: allow Windows to install all drivers. One of the drivers may not be found and will require you to go to the Window’s Device Manager under the Control Panel. There, you can locate the device (having a yellow warning icon next to it) and right-click on it.
  2. Choose to “update/install” the driver for your device.
  3. Go to your desktop. Open the Android SDK folder and select SDK Setup.exe.
  4. Allow it to automatically refresh its list of the operating system SDKs that are available, and select to install all packages.
  5. Once finished, exit the application.
  6. Go back to the opened Android SDK folder on your desktop, and open the “Tools” folder.
  7. Click on the file ddms to open the Dalvik Debug Monitor.
  8. Select your device from the “Name” pane.
  9. In the application’s top menu, open the “Device” menu, and choose “Screen capture…” A Device Screen Capture window will open, and you should see the launch screen of your Android device.

Screenshot29
The Dalvik Debut Monitor.

To navigate:

  1. Grab your Android device and navigate to any page. Go back to your computer and select “Refresh” in the Device Screen Capture window. The current screen from your Android device should appear.
  2. If you’re on a Mac, you can just do the old Shift + Command + 4 trick to take a screenshot. In Windows, you can copy and paste it into one of the Windows media applications.

About Android Tablets

At CES 2011, companies rained down Android tablets30, with an array of screen sizes. However, after a quick review of the most popular ones31, we can conclude that the two important screen sizes to focus on in terms of physical pixels are 1280 × 800 and 800 × 480.

With the Android 3.0 Honeycomb release, Google provided device makers with an Android UI made for tablets. Gone is the hard “Back” button, replaced by an anchored software-generated navigation and system status bar at the bottom of the screen.

Screenshot32
The anchored navigation and system bar in Android 3.0.

Android 3.0 got a visual refresh, while incorporating all of the design patterns introduced in Android 2.0. One of the major differences with 3.0 is the Action Bar which has been updated to include tabs, drop-down menus or breadcrumbs. The action bar can also change its appearance to show contextual actions when the user selects single or multiple elements on a screen.

Screenshot33
The new action bar with tabs, introduced in Android 3.0.

Another new feature added to the Android framework with 3.0 is a mechanism called “fragments34.” A fragment is a self-contained component in a layout that can change size and position depending on the screen’s orientation and size. This further addresses the problem of designing for multiple form factors by giving designers and developers a way to make their screen layout components elastic and stackable, depending on the screen limitations of the app. Screen components can be stretched, stacked, expanded and collapsed, and revealed and hidden.

Screenshot35
Diagram showing examples of how fragments can be used.

The next Android release, scrumptiously dubbed Ice Cream Sandwich36, promises to bring this functionality to Android smartphones as well, giving designers and developers the option to build an app using a one-size-fits-all strategy. This could be a paradigm shift for designers and developers, who will need to learn to think of app design in terms of puzzle pieces that can be stretched, stacked, expanded or hidden to fit the form factor. In short, this will allow one Android OS to run anywhere (with infinite possibilities!).

A Word of Advice

Do get your hands on an Android phone and tablet, and spend some time downloading apps and exploring their interfaces. In order to design for Android, you have to immerse yourself in the environment and know it intimately. This might sound obvious, but it’s always surprising to hear when even the product manager doesn’t have an Android device.

Screenshot37

Online Resources

Here are some links to online resources I’ve found especially useful:

Presentations

Videos

Documents

Blogs

Product Reviews

Android Developers

Other

(al) (il) (kw)

Footnotes

  1. 1 http://en.wikipedia.org/wiki/IOS_%28Apple%29
  2. 2 http://www.pcworld.com/article/226339/android_market_share_growth_accelerating_nielsen_finds.html
  3. 3 http://en.wikipedia.org/wiki/Comparison_of_Android_devices
  4. 4 http://developer.android.com/guide/practices/ui_guidelines/index.html
  5. 5 http://en.wikipedia.org/wiki/Quarter_Video_Graphics_Array#QVGA_.28320.C3.97240.29
  6. 6 http://www.smashingmagazine.com/wp-content/uploads/2011/06/t-mobile-g1.jpg
  7. 7 http://www.smashingmagazine.com/wp-content/uploads/2011/06/screen-sizes.gif
  8. 8 http://developer.android.com/resources/dashboard/screens.html
  9. 9 http://www.smashingmagazine.com/wp-content/uploads/2011/06/table.png
  10. 10 http://developer.android.com/guide/practices/screens_support.html
  11. 11 http://code.google.com/p/svg-android/
  12. 12 http://www.smashingmagazine.com/wp-content/uploads/2011/06/density-test-bad.png
  13. 13 http://www.smashingmagazine.com/wp-content/uploads/2011/06/icon-sizes.jpg
  14. 14 http://www.smashingmagazine.com/wp-content/uploads/2011/06/folders.gif
  15. 15 http://en.wikipedia.org/wiki/WebKit
  16. 16 http://www.smashingmagazine.com/wp-content/uploads/2011/06/back-key.jpg
  17. 17 http://www.smashingmagazine.com/wp-content/uploads/2011/06/pattern-dashboard.jpg
  18. 18 http://www.smashingmagazine.com/wp-content/uploads/2011/06/pattern-action-bar.jpg
  19. 19 http://www.smashingmagazine.com/wp-content/uploads/2011/06/pattern-search-bar.jpg
  20. 20 http://www.smashingmagazine.com/wp-content/uploads/2011/06/pattern-quick-actions.jpg
  21. 21 http://www.businessinsider.com/best-android-widgets-2011-4
  22. 22 http://www.smashingmagazine.com/wp-content/uploads/2011/06/pattern-widgets.jpg
  23. 23 http://www.droidfonts.com/home/androidsdk/
  24. 24 http://developer.android.com/guide/practices/ui_guidelines/icon_design.html
  25. 25 http://android-ui-utils.googlecode.com/hg/asset-studio/dist/index.html
  26. 26 http://developer.android.com/sdk/index.html
  27. 27 http://www.oracle.com/technetwork/java/javase/downloads/index.html
  28. 28 http://www.smashingmagazine.com/wp-content/uploads/2011/06/settings.jpg
  29. 29 http://www.smashingmagazine.com/wp-content/uploads/2011/06/dalvik-screen.png
  30. 30 http://www.engadget.com/features/tablets-at-ces-2011/
  31. 31 http://reviews.cnet.com/best-tablets/best-5-android-tablets
  32. 32 http://www.smashingmagazine.com/wp-content/uploads/2011/06/system-bar.jpg
  33. 33 http://www.smashingmagazine.com/wp-content/uploads/2011/06/new-action-bar.jpg
  34. 34 http://android-developers.blogspot.com/2011/02/android-30-fragments-api.html
  35. 35 http://www.smashingmagazine.com/wp-content/uploads/2011/06/fragments.gif
  36. 36 http://gizmodo.com/5800358/what-is-androids-ice-cream-sandwich
  37. 37 http://www.smashingmagazine.com/wp-content/uploads/2011/06/android-ice-cream-sandwich.jpg
  38. 38 https://docs.google.com/fileview?id=0B9Lrx2XbHPV6NTBiYTA5OGMtYmEwNi00Yzc3LWIxNWUtZWYwZGZlZGViZWMz&hl=zh_CN
  39. 39 http://www.slideshare.net/AndroidDev/android-ui-design-tips
  40. 40 http://www.google.com/events/io/2010/sessions/android-ui-design-patterns.html
  41. 41 http://www.youtube.com/watch?v=WGIU2JX1U5Y&feature=player_embedded#at=3469
  42. 42 http://en.wikipedia.org/wiki/Comparison_of_Android_devices
  43. 43 http://anidea.com/technology/designer%E2%80%99s-guide-to-supporting-multiple-android-device-screens/
  44. 44 http://www.androidpatterns.com/
  45. 45 http://www.androidpatterns.com/
  46. 46 http://reviews.cnet.com/best-android-phones/
  47. 47 http://reviews.cnet.com/best-tablets/best-5-android-tablets
  48. 48 http://developer.android.com/guide/practices/screens_support.html
  49. 49 http://developer.android.com/guide/practices/ui_guidelines/icon_design.html
  50. 50 http://developer.android.com/sdk/android-3.0-highlights.html
  51. 51 http://speckyboy.com/2010/05/10/android-app-developers-gui-kits-icons-fonts-and-tools/

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Born and raised in Silicon Valley, Daniel McKenzie is a digital product designer helping startups and companies strategize and design products that matter. He also likes to write and tweet (@danielmckenzie) on various design and innovation topics.

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  1. 1

    Hey Stefano, where does the denumeration 3 (800/3 and 480/3) came from ? can you show me how to convert from 6 (HDPI) to 3(LDPI) ?

    thanks

    0
  2. 52

    this is a very good articles. I always have a problem to design on Android due to different resolutions. Its easier to design on iOS. :)

    0
  3. 103

    QR code is a great invention people made. I’m making mobile apps currently and find it really cool to implement QR codes into them. I’m amazed at QR code coupons Snappii app builder allows to create. They are really helpful for small businesses.

    1
  4. 154

    Great article! Had so much confusion…

    0
  5. 205

    By the comments left here or just the hideous interfaces I’ve seen… the real problem seems to be the Android SDK. It doesn’t have to be this difficult. Since when are raster on-screen graphics referred to in DPI? This means I can’t do pixel level graphics because they may be interpolated to the nearest resolution… very odd. Could you imagine if web design was like this? And web pages (usually) have to accommodate for every possible size (resolution.) I would have rather seen supported resolution asset folders (i.e. 640×480) instead of using the ldpi, mdpi, hdpi, etc asset folders. At least then you’d have concrete numbers to work with (like iOS.) I appreciate the article though (very informative.) I just wish it wasn’t necessary.

    1
  6. 256

    About screen density and size : I just finished a tool to help me (and could help other people too) to generate their images easily
    http://code.google.com/p/9patch-resizer/
    Feedback is always appreciated ! (Resizes xhdpi .png or .9.png to other densities)

    -1
  7. 307

    Web design already *is* like this. Mobile Safari and the Android Browser employ the very same mechanism that is in place in Android (and actually in iOS too, for that matter. The only difference between iOS and Android is that iOS has two target densities (MDPI and XHDPI) while Android has four. Really not that complicated).

    The reason is that you do not want the same behavior websites and applications used to have on the desktop: That the higher your screen density gets (which should be a good thing), the smaller your UI becomes (which is a bad thing). This would be disastrous on a touch screen device. Your fingers don’t automatically get smaller just because your pixels did.

    Instead, you define elements to have an actual, physical size. A button that is 2cm on one Android device is also going to be 2cm on any other device, no matter its screen properties. And this is a very, very good thing. Usability > Pixel perfect graphics.

    0
  8. 358

    There’s a problem with this article i think
    Originally the baseline talked about is at 320×533 which makes sense to me as proportionally its the same as 480×800

    However later on the article says
    “(remember the “baseline” is a layout set at 320 × 480)”

    Which is it???

    And if it is 320×533…. how does one scale their stuff for a 320×480 screen? We’re losing height there…. hence losing space on the screen for our elements, meaning on a screen where the user doesnt scroll down… wehave less space to play with
    ?

    Want to get htis perfect but due to conflicting advice around different tech forums — its v tough. This article is great – until i spotted the conflicting advice within the article itself

    Whats the baseline 320×480 or 320×533?

    0
  9. 409

    Research what you are talking about before making an asinine comment like that.

    http://en.wikipedia.org/wiki/Dots_per_inch

    http://developer.android.com/guide/practices/screens_support.html

    1
  10. 460

    Can’t I just design my graphics large and high quality, and have Android scale them down as needed.

    For example, if different devices require an icon to be 32×32, and 48×48, and 96×96, then why can’t I just create ONE nice transparent png icon that is 200×200 and set the relative size of it in the code, and be done?

    Or am I missing something?

    0
  11. 511

    We’ve taken a close look at Android vs. iPhone on our site. Android is now well ahead of the iPhone in the mobile OS wars. Please review our take on the subject of Android vs. iOS.

    http://interpixdesign.com/_iphone-vs-android-app-design

    0
  12. 562

    You could do that but its likely that your scaled images will look blurry or pixelated. Similarly, you could design solely for mdpi and Android will automatically scale up/down for hdpi/ldpi. You can usually get away with this without the image quality being affected too much. The result is obviously going to be less desirable the more scaling that is involved. The same degradation of quality will still occur if you manually scale your images with Photoshop but I think their algorithm is better.

    I think the “best solution” for having “perfect” images regardless of the DPI is to design your graphics using a format like SVG and then to export to the size you need.

    Personally I think all of this is more trouble than its worth. I use a combination of the two approaches. I design my graphics using SVG and export to mdpi and allow Android to do the scaling itself. If the result looks poor then I can always export to the size I need and drop it into correct res/drawable folder.

    0
  13. 613

    Please give me tips I am new in android . Please see this http://thedroidcity.com/ and share suggestions .

    0
  14. 664

    this site may help you for the other custome development.
    http://learnandroidfree.blogspot.in/

    0
  15. 715

    thanks for sharing, may be useful.

    0
  16. 766

    Love it..

    0
  17. 817

    Dan,

    I must say the article is much neat that the android’s design guidelines. I was strolling on android’s site and though things are placed in tidy way, the concepts messed up.

    And you cleared up that mess in my mind

    Thanks much.
    Aniket

    0
  18. 868

    Hi, I am developing a website optimized for mobile devices (web browsers), I am developing clickable interface (i.e. images used as buttons) I need to know, what size in pixels (width and height) should I adopt so that it is easy to tap using finger.

    My website that I need to be optimized is urdujini.com/phansighar/urdu_hangman.asp

    Waiting for your guidance.

    Thanks in advance
    Naseem

    0
  19. 919

    That’s a cool writing on designing for android and how to do it in detailed process . i am also a Android geek and i have my own blog at AndroidShouters.Com
    here i also share news and trends on Android .

    Thanks for sharing your awesome guideline on designing for android again..

    -1
  20. 970

    My family members all the time say that I am wasting my time here at net, however I know I am getting familiarity all the time by reading thes good posts.

    0
  21. 1021

    The negative with all these tools is that they don’t integrate with the operating system. One of the biggest temptations for a new Spanish student is the desire to jump straight into conversation. Just pick what you want to send, then position the phones closely and gently bump hands with another Bump user.

    0
  22. 1072

    Asking questions are genuinely nice thing if you are not understanding anything completely, except this post provides nice understanding yet.

    1

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