Most AR apps focus on taking images of the real world and overlaying graphical effects using your device's screen. Track Builder eschews the camera tricks and instead focuses on creating a boy's playroom for you to explore physically. You move the phone up and down and even walk all over to look at all the furniture and decoration in the space, though most of your focus will be on the Hot Wheels track you can construct on the long table in the center.
The app gives you plenty of bright orange track to build with, and also allows you to place ramps and obstacles for your virtual course as well. To get a good look at your work, you'll have to actually walk around the table, just like if you had put together a plastic Hot Wheels set in your house.
There don't seem to be any plans to create any real world overlays just yet, so you can't pretend to put together a course on your coffee table or bedroom rug. But the app does incorporate the best part of building any Hot Wheels track: the testing phase. You can pick out classic Hot Wheels vehicles and pit them against your creation. And, just like the real world version, you do need to use a little finesse when racing; too much power can send a car flying off course. The good thing about Track Builder is that because the cars aren't real, you don't have to worry about younger brothers or sisters getting hit in the face with a flying Ferrari.
Hot Wheels Track Builder is available now, but there's only one phone out that supports it. Hopefully we'll see more devices to build a track with unveiled at next month's Mobile World Congress.