Finally you ascended.
Kids doing augmented reality shenanigans is quite an apt description for the beginning but even within the first episode it should be apparent that there's more than just that. OP and ED are quite telling, too.
Also, while they're kids, they actually do behave appropriately as such. There's too many anime with characters being kids only in name when they're really behaving like late teens.
edit: Just swapped my avatar to honor one of the best designed entities in anime!
There were a few scenes that hint to something more serious but they were but a drop in the ocean. Especially if you count #03 and #04 too.
I still gotta do my writeup on this show. Even took a lot of screenshots but then didn't quite know what to write *shrug*.
This reminds me I never managed to write something about Steins;Gate's ending. ;o