March has been busy for Google. At the beginning of the month the company launched the first Developer Preview for Android P, and then, a couple of weeks ago, rebranded Android War to Wear OS.

And now, Google is back with another first Developer Preview, this time for Wear OS. The new software brings with it a few key features, including a new system-wide dark UI, as well as plenty of behind-the-scenes additions that should make using a Wear OS smartwatch a bit nicer.

Here are the new additions:

• Restriction related to non-SDK methods and fields: To improve app compatibility, Android P has started the process of restricting access to non-SDK methods and fields. Developers should make plans to migrate away from these. If there is no public equivalent for your use case, please let us know.
• Dark UI system theme: To enhance glanceability, Wear OS has switched to a UI theme with a darker / black background for the notifications stream and system launcher since the start of the year. This is now also the default for the system theme and should improve the glanceability for wear apps. Developers should check the accessibility of their app’s UI after this change.
• Limited background activity: To improve power, apps will no longer be allowed to run in the background unless the watch is on the charger. Developers should note that Wear OS is going further with Android’s app standby feature than some other form factors. Exceptions to this include watch faces and complications that the user currently has selected. This feature will be rolled out gradually in the developer preview, so you may not see it immediately on your device, but should build your apps accordingly by removing background services.
• Turning off radios when off body: To improve power, bluetooth, WiFi, and cellular radios will be turned off when the watch is detected to be off body for an extended period of time. Again, this feature will be rolled out gradually so you may not initially see it on your device. If this feature causes challenges in your development process, you can disable the feature via adb; please follow the instructions in the release notes.
• WiFi off when BT is disconnected: To improve power, the device will no longer automatically connect to wifi when disconnected from bluetooth. Exceptions include if an app is requesting a high bandwidth network or if the watch is on the charger. This feature will be rolled out gradually so you may not initially see it on your device.

The first Developer Preview for Wear OS includes downloadable system images for the Huawei-branded Watch 2 and Watch 2 Classic.

It is available now.