Good interfaces should be designed around an economy of clicks. Or in the case of the iPhone, an economy of taps. Put simply: apps should allow users to achieve key goals with as few finger taps as possible.

Exit Strategy NYC’s extremely simple interface asks only three key pieces of information:
1) What subway line are you riding? (tap the line’s icon)
2) What subway station are you going to? (tap the station)
3) What is your direction of travel? (tap ‘uptown’ or ‘downtown’)

The app then shows the platform diagram for this station. Three taps — that’s it! In and out in fewer than ten seconds. Compare this to the Tube Exits interface design (Tube Exits is the London equivalent of Exit Strategy NYC.) The user has to tap over a dozen times just to get the same information!

One of my favorite apps, Foursquare, took a step backwards in their latest update. Previously you could check in with two taps: once on the venue, and once on the ‘check-in’ button. Easy Peasy. But the latest update added an additional step after the ‘check in’ button. This change added no functionality, only friction.

If you’ve ever played the Settlers of Catan iPhone app, you’ve seen another worst case scenario. Users must tap a tiny “Continue” button every time the next player’s turn comes up. It’s unnecessary and it’s frustrating.

Using an app with poor tap economy is like trying to run a marathon in the ocean. You exert much more effort and get nowhere fast. There’s too much friction. Tapping is mentally taxing, especially when it lands users on an entirely new screen. The user must review this new screen, then figure out which elements are interactive, then decide which one will help achieve their goal, and then tap again! Each additional screen/tap shoves one more roadblock between the user and their end goal.

The best services let users do more by doing less. This makes users feel powerful. Have you ever used Amazon’s one-click checkout to place an order? If not, please try it. It’s thrilling to use! Similarly, Griffin’s iTalk app features a giant ‘record’ button that feels magical. With a single tap, the user can start recording because the app picks smart defaults and stays out of the way.

The only time having an extra tap makes sense is when the alternative is worse: a cluttered user interface. Good UIs balance which elements are shown and which are hidden. Consider Facebook’s decision to add the grid button in the upper left corner:

Economy [of taps] is always a motivating factor, but the grid adds an extra tap [because you need to press the grid button] versus the full-time tab bar. This was a compromise I felt was necessary. There’s always that balance between screen clutter–adding tabs–and the number of taps.

-Joe Hewitt Quoted in Chris Dannen’s iPhone Design – Award Winning Projects

At the heart of many apps is a single core goal that your users hope to achieve — repeatedly. For Exit Strategy NYC it’s retrieving information. For iTalk it’s recording audio. For Foursquare it’s checking in. For Amazon it’s purchasing items. Don’t make your users run in the ocean. Remove as much friction as possible. Let them fly in the sky! The quicker the user can perform their goal, the better they feel about themselves. And the better your product makes them feel, the more they’ll fall in love.

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