It's not enough to start a fire--you got to feed it too. Amazon is feeding its Fire Phone a handful of new features with the Fire OS 3.5.1 software update. The update will be automatically downloaded and installed to your Fire Phone over Wi-Fi. Or if you're the impatient type (where's the Fire... OS), you can manually download it to your computer, connect your Fire Phone with a USB cable, and install it yourself. If you want to see which version of Fire OS you have, head to Settings > Device > Install System Updates to check.
The update adds a number of small but useful features--I covered some of them in a tips and tricks slideshow earlier this month, since Amazon included Fire OS 3.5.1 on Fire Phone units sent to media for review. This means that early adopters didn't get some of the extra bells and whistles that reviewers experienced, including "dozens of system updates for enhanced battery performance." Still, better late than never.
Aside from the battery life improvements, Fire OS 3.5.1 brings the ability to delete email from the carousel on the home screen. You'll see a preview of new messages below the Email app's icon, and you can swipe from right to left to delete them without ever opening the app. When you do open the app, they'll be in the Trash folder, in case you delete one by mistake. (Pro tip: Deleting email is almost never a mistake.)
You can also pin an app to the front of the carousel. Typically, the carousel shows your recently used apps in order: the last app you used is always at the front, followed by the second-to-last app, and so on. But if you're, say, traveling, you might want the Maps app pinned to the front of the carousel all the time. All you have to do is tap and hold an icon in the carousel and select Pin to Front. That same menu has a Remove from Carousel option, too. The update also lets you create folders in the app grid by dropping icons on top of each other, and quickly switch between apps with a double-press of the home button.
In the Camera app, you can now create "Lenticular" photos with 11 stills instead of three. This mode works similarly to stop-motion animation apps like iStopMotion for iOS: After you snap one picture, the subject remains "ghosted" on the screen just a little bit, so you can move the camera or the subject slightly and take another photo. When you're done, the app combines these photos like a flipbook image, letting you make little animations. You preview them by tilting your phone, replace any frames you don't like, and export the whole series as a GIF. It's kind of fun to play around with, but making something cool can take a lot of trial and error.