Every once in a while, an idea comes along that is so brilliant and yet so obvious, you almost smack your hand against your head in amazement. Kid’s Corner, a new feature in Windows Phone 8, is such an idea. How did we live without this?

For the past couple of years, I’ve fielded the variations of the same question repeatedly about Windows Phone: Is there any kind of parental control or multi-user functionality? The answer was always no, at least during the Windows Phone 7.x time frame, but I didn’t quite understand the point: Smart phones, after all, are very personal devices, and they’re expensive, with monthly data fees. Who would share such a thing with someone else, especially a child?

Pretty much any parent, as it turns out. No, smart phones aren’t doled out like tablets and iPods. But anyone with kids has been in that situation in a restaurant, line, or other public place where a child is getting antsy and you hand them the phone in order to keep them in line.

The trouble is, your personal and professional data is on there. You don’t want them messing with that, or seeing something they shouldn’t see, whether it’s in your email, on the web, or elsewhere, or buying apps or music online. My kids, now aged 14 and 11, are pretty much old enough that I’m not as worried about this as I used to be. But it wasn’t always that way: Over two years ago, my kids racked up almost $900 in iTunes in-app purchases, as I wrote in So Easy Even a Child Can Do It. You don’t want to be a statistic.

So for Windows Phone 8, Microsoft has created Kid’s Corner. And it’s a great feature, one that every parent should investigate.

Kid’s Corner separates your phone into two environments: The full phone experience, for you, and protected by a PIN. And a new children’s environment, called Kid’s Corner, which includes just the apps, games, movies, and music that you want them to access.

Because not everyone will want Kid’s Corner, the feature is disabled by default. You enable it in Settings, System, Kid’s Corner. All you need to do is step through a short wizard that explains the feature and provides you with a way to choose the games, music, videos, and apps you wish to make available to your children.

In each case, you’re provided with a list of items, none of which are checked. Just check the items you wish to make available.

When you’re done, Kid’s Corner is ready for use. From your lock screen, instead of swiping up to enter your PIN, you can swipe from right to left to enter Kid’s Corner.

After swiping up on that Kid’s Corner lock screen—there’s no PIN—you’re presented with a very simple Start screen that only includes those items you allowed. Kids can also take pictures with the device’s camera.

A special Customize tile helps your kids personalize Kid’s Corner. They can change the name (from Kid’s Corner), choose a picture for the lock screen, and pick their own color scheme (background and accent color) combination.

Note: Certain items are not available in Kid’s Corner, including Internet Explorer Mobile, Phone, and Messaging.

To close Kid’s Corner, just press the device’s power button.

A couple of closing notes about Kid’s Corner.

First, you can only create one such environment on your phone. So if you have multiple kids, they’ll need to share.

Second, if you do share apps or games with your kids, they will see the same in-app state that you do. That is, Windows Phone is not a true multi-user environment, so if you have, say, certain audio books open in the Audible app, those same audio books will appear if your kids use the app too.