Apple’s first objection to my folding-phone protractor was the word “Duo.”

I’d called it Protractor Duo: Angle Finder. It measures the opening angle of an iPhone Duo. Seemed reasonable enough.

New hardware, small apps

I built Torchlight when the iPhone 4 arrived with an LED camera flash. It was the first iPhone with one. Keeping that LED on gave the phone another use: a torch.

The Duo is Apple’s first foldable iPhone, and its hinge gives an app something new to measure. Protractor follows the same idea as Torchlight: take a new piece of hardware and give it a useful job.

A good reason to build for my most expensive phone yet: a $2,000 replacement for a $2 protractor.

Then came the name

Apple rejected the name under guideline 5.2.5:

Terms for ‘Duo’ in the app name in an inappropriate manner.

Apple lists iPhone Duo™ in its trademark list, with no separate entry for “Duo.”

I don’t think “Protractor Duo” infringed that trademark. The rejection doesn’t settle the legal question, either. But getting onto the App Store means meeting Apple’s own rules, which prohibit using its trademarks “in whole or in part” in another product’s name.

We’re at Apple’s mercy for approval. With the iPhone Duo about to reach customers, I wanted the app ready for those first owners. Arguing over the name could cost us that launch window.

And so I dropped the Duo, and Apple approved it - Protractor°