Augmented Reality games use your ACTUAL environment as a BASE for your game’s environment. So, it will always be played outdoors. They use GPS to map your local area, then make it as a basis for your game’s actual map, then eventually augment it by adding special stuffs. Like in the case of Pokemon Go for example; let’s say that your actual backyard is a gym in the game. So, everyone in your neighborhood who plays Pokemon Go will detect your backyard as a gym as well. To make it simple, your actual environment becomes the playing grounds not just for you, but for everyone in your neighborhood playing the game. The reason why Augmented Reality games will always be played outdoors, well at least, best played outdoors.