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Here’s the full FAQ…

What is the Mirror mode?

This setting setting helps you catch anyone that might try to steal a couple of dollars from you by messing with the receipt. Let’s say you filled out your receipt like this:

SUBTOTAL:  $18.50
TIP:      $3.00
TOTAL:    $21.50

Now imagine that evil waiter Joe changes it:

SUBTOTAL:  $18.50
TIP:      $8.00
TOTAL:    $2b.50

You may think that the letter “b” looks nothing like a 6, but Joe won’t have to write using the Courier font and his forgery will be a tad more realistic.

The Mirror mode will adjust the tip amount so that the digits that make up the total are in the same sequence whether they’re read forwards or backwards. check out the receipt shown above, mirrored:

SUBTOTAL:  $18.50
TIP:      $2.62
TOTAL:    $21.12

By turning the number into a palindrome, you can scan all food charges in your credit card bill and determine if anyone scammed you without doing any math.

Behind the scenes, the App is adjusting the calculated tip either up or down to reach a palindrome, choosing whichever of the two results will change your total by the smallest amount. if you’re concerned about under- or over-tipping while using the Mirror mode, you can tweak the Tip % slider appropriately.

Can you add Tax calculations?

I’ve tried some sample calculations and discovered that typical tax rates have a negligible effect on the total. For example, a meal of $50 dollars, tipping 18% and with a tax rate of 6.25% would cause a difference of less than 67 cents.

The best feature of this App is this simplicity and the benefit doesn’t seem to be worth jeopardizing it. Obsessive penny-counters don’t despair — I’m exploring a couple of ways of adding tax-awareness to the tip calculator in a way that doesn’t mess with the inferface.

What’s with the ‘∞’ in the name? Bowtie Infinity?

Pretend it’s a bow tie.

I hate/love the icon!

Did you just try to ask a non-question? And with a slash in it no less. The icon has gone through many iterations and refinements and it’s pretty much locked for now. If you have specific suggestions I’d love to hear them but don’t let a wave of disappointment wash over you if all that you see is a different background color in the next release.

How can I use the Tip App when everyone in my party wants to tip different percentages?

The best way to do that is to use the Exact method, set the tip to 0% and split based on the number of people in your party. The total shown below will be the even split for each person, then, each one in your party can tip as they wish.

Can you add an option to round up or down?

The app is smart enough to choose rounding up or down — whatever it takes to tip as close as possible to the exact percentage you desire. My rationale is to make the app smart and uncluttered so you don’t have to think about the details of these decisions. Note that if the rounded tip is too different from the tip you desired, you’ll see the Effective Tip percentage displayed at the top of the screen.

That’s all for the FAQs for now. If you have any other questions, don’t hesitate to email me. And finally, like any other App Store developer, I humbly grovel for your reviews.

Little things are often the most helpful,
and because they’re so little, they know when to get out of the way of your eye.

Details of my obsessions with tiny media controls after the jump…

The beginning of the scrubber track is subtly broken off into a “rewind to beginning” button, so users don’t have to drag reassuringly into the start of the timeline or guess whether they are clicking at the start or 2 seconds into the video clip.

When the scrubber is dragged to a part of the timeline that hasn’t been downloaded yet, it changes to a “concerned” appearance. this sets user expectations, so they’re clear some buffering is inevitable.

As the video is downloading, the leading edge (that shows how much as been loaded) gently undulates to show that more bits are coming in. The undulation can even be stretched proportionally to visualize the speed of the incoming data and give an idea of how much more footage will be available in, say, one minute from now.

<video onStalled="videoScrubber.stopUndulating()" />

I bet it wouldn’t take much extra work on top of HTML5 to build this, I wish I had the attention span to find out…

Screens by our kick-ass visual design team (based on my wires).

More behind-the-scenes pics and a neat video, after the jump…

The challenge with this design was to build something that required zero training and delivered engaging content in the 30-odd seconds that it would hold user’s attention.
Here’s a few of my wireframes:

And here’s more stunning comps by our visual design crew:

We ran out of development time to build the rotate-and-drag interactions shown in the wireframes above (which would have been a bit more organic) but the developers did a stellar job:

That’s me, playing around with the real app!
HTML5-friendly browser required to play this video, or try an MP4 download.

Lastly, here are the adoring throngs fawning over the kiosk, already inset in its housing, ready for the masses:

I helped build a diagram that shows consumers moving through promotional and e-commerce websites to arrive at a desired outcome, and then I gave it a horrible, horrible name…

This is the Slaughterhouse Floorplan for Nike Soccer’s MySpace page which had the important task of funneling visitors to their YouTube page and the Nike Store (ka-ching!).

This huge one models all the moving pieces of the Microsoft KIN's marketing campaign:

I tried my best to point out the “gaps” — the leaks in the purchase funnel if you will…

…you know the rest of that story. C’est la vie.