"Grownups" is my favorite xkcd comic. Let's see your take on it. :)
It's . . . very different from the comic. "Based loosely" is right.
The game itself is extremely simple to the point of being disappointing. The playpen balls are nice and colorful, but the game amounts to just finding three randomly-placed phones in a very small area. There's not a lot to it.
Not much more to say--it's a simple, quick game that doesn't demand much of you, nor does it take much of anything from the comic it's based on aside from the playpen setting.
(Btw, what is an "xkcd phone" you talk about in the description, and how can I get one?)