In Windows 8.1, Microsoft has changed a key behavior of Metro-style mobile apps: When you drag from the top of an app down to the bottom of the screen, it no longer closes the app. And thanks to an interesting addition, you can optionally restart an app this way now as well.
Thanks to Jeremy N. for the tip.
If you had used Windows 8 (or RT) previously, you know that one of the ways in which you could close an app was to drag from the top of the screen to the bottom of the screen. While doing this, the app would visually shrink to a thumbnail image and then disappear, indicating that you were closing it.
You can still do this in Windows 8.1—and it works via touch or the mouse—but if you check Task Manager afterwards, you'll discover that the app didn't really close. All you did was exit from the app, and the OS will manage it from there.
But in addition to changing this behavior, Microsoft added a new feature: You can now use this drag action to restart the app too. To do so, drag from the top of the screen to the bottom as before. But instead of releasing the app thumbnail as before, pause and hold. As you do, the app thumbnail will visually spin in place, and you will see its splash screen appear.
Now, release the thumbnail. The app will start up again, as if from scratch.
Alternatively, continue to drag the thumbnail off the screen after the flip animation and the app will close like it did in the original shipping version fo Windows 8.
This is an interesting change. I'm wondering if there is any more information out there about it.
Update: Matt G. notes via email that by keeping the apps alive in this fashion, Microsoft could give the appearance that they were opening faster on subsequent launches (as opposed to the slower "cold" launch). I think that makes sense, as does his assertion that it would then need to provide a mechanism to re-launch the app if it were in a bad state without having to drop back into Desktop and fire up Task Manager--hence the pause and hold. Thanks, Matt.