New Software Kit Tells a Lot About the Apple Watch In addition to a developer's kit, Apple released a set of public documents that reveal a lot about how the new device works.

Apple opened up its Software Development Kit, dubbed Watch Kit, to developers on Tuesday for coders looking to create apps for its upcoming Apple Watch.

While SDK is only available to app developers, the iPhone maker also released a set of public documents that accompany the kit and they reveal a lot about how the new device works.

Here are a few highlights the documents and the introduction video, which were first reported on The Verge.

Apple Watch only works with an iPhone

The app runs with an iPhone extension, which supplies the processing power. "A Watch app complements your iOS app; it does not replace it. If you measure interactions with your iOS app in minutes, you can expect interactions with your Watch app to be measured in seconds, " Apple said in the documentation.

Native apps coming soon

Starting later next year, developers will be able to create, what Apple refers to as "fully native apps" for the device.

More info about display specs

As previously disclosed, the watch's will be available in two sizes, 38mm and 42mm. The smaller device's screen has 272 x 340 pixels, and the larger one features 312 x 390 pixels, according to the SDK. The screen on both devices will have a aspect ratio of 4:5.

In addition, developers have the option to enable the glance feature, allows users view apps in quick view mode by simply holding up the device.

Apple leaves the door open for additional sizes

The device's design makes it easier to update. It loads like a responsive website, with objects filling the screen in a downward motion. "That'll make things a lot easier for developers and a lot nicer for watch owners should Apple decide to make a change," The Verge reports.

Click here to read the full list from The Verge.