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Last month Apple released WatchKit, its software-building tool for Apple Watch, and developers are already lamenting its limitations.

One iOS developer summed up those limitations perfectly, comparing development for the Apple Watch to building a car.

"It's like saying you can build and design any car you want, but ultimately it has to go inside one of two body styles," our source said. "You can still do a lot of great work with the engine and interior, but if in the end it looks like everything else ... then where's the fun?"

In this analogy, the two body styles are the two app navigation styles that Apple has made developers choose between: hierarchical, and page-based:

The hierarchical style is like a choose-your-own-adventure. Users will make one choice on each screen until they reach their destination.

Page-based apps will be better for horizontal swiping through data that's not related to what's on other screens.