If you don't struggle to get up in the mornings, we salute you; if you do, then this could come in handy for forcing you out of bed.
Google — unlike Apple — updates its stock apps separately from the main Android OS. That means there won't be as much to talk about for Android 6.0 Marshmallow as there was for iOS 9, but it also means we get plenty of app upgrades spread throughout the year. Google's Clock app recently got an upgrade with a couple of useful new features. One of them is the option to set an alarm that gets gradually louder and louder over time.
From the Alarm page, tap the menu button (three vertical dots) and choose Settings to find the toggle switch.
Of course, Android alarm clocks from other developers have been doing this for a long time, but now it's officially included in Google's own app. As Engadget notes, other upgrades include better Android Wear support, the ability to preemptively dismiss alarms from inside the app, and improved timer management from the notification drawer.