Lego has launched a new iOS app that uses mixed reality to bring physical sets to life.

Lego Playgrounds is built using Apple's ARKit and will be constantly updated with new games and experimental features.

Previously shown in concept form at WWDC earlier this year, the app is a free download and uses augmented reality to place interactive, digital elements and games onto real-world surfaces.

Where it differs from many other AR experiences is that it recognises physical Lego playsets and uses them as part of the fun.

The first playgrounds experiment focuses on Lego Ninjago and the Dragon Hunters sets in the range. The app can be used to add items and characters to a built set, which can be played solo or with a friend on other iOS device in the same location.

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You can even play five levels of the built-in game without needing a physical Ninjago set to get used to the options on offer. All you need in that case is a flat surface to scan and play on.

The current sets recognised by the Lego Ninjago AR Playground experiment are the the Lego Ninjago Dieselnaut (70654) and the Lego Ninjago Dragon’s Pit (70655).

There are no in-app purchases in the Lego Playground app and it is open to all ages. However, the Ninjago AR elements are recommended for ages 9 and up, due to some content. It works on iPad and iPhones from the iPhone 6S and up.