Play it if: a character-centric, puzzle-less story told in an interesting way sounds like your cup of tea.
Don't play it if: you're hoping for a genuinely engaging character drama, because this is more of a snapshot than a full-blooded story.
In Common Ground we have an interesting fusion of structure and content. The story is told as a re-tread of the same brief time period from the viewpoints of different players. With the game collecting information about your chosen actions in successive iterations, the perspectives never contradict one another in the broad outline of what goes on - though their subjective filters of what is happening will flavor how characters deliver dialogue, or if they even say certain things at all. The unreliable, non-linear narration is strongly reminiscent in places of the previous year's Spider's Web, though the focus here is on character and there is no explicit requirement that the player remain consistent with the details of the pre-determined narrative.
If there's a flaw in how it's employed here, it would have to be in the fact that the story very much emphasizes the thoughts and intent of one character above the others. The scene is divided between two characters other than the protagonist, and as such they are less well served in the story than they might have been if the plot had only switched between Jeanie and one of her parents.
This is a device which has been seen before and since in other media, but not particularly often, and it is a device which I find suitable to IF. Bearing in mind that the "fuzzy memory" nature of the plot allows for an imperfect recollection of game events, it's still technically notable.
The story itself is perhaps less interesting than the way in which it was presented. In the initial stages, at least, I found it reminiscent of Flannery O'Connor's "Where Are You Going, Where Have You Been?" Like O'Connor, Granade is effective at revealing his female protagonist's character through her reactions to her environment. Jeanie entertains impossible dreams, like appearing in a Bon Jovi music video, and as a result is reluctant to praise much of anything in her actual environment, including her parents. She consistently refers to her mother's husband as "Frank", which is interesting for two reasons: a) she's known him since at least six, and b) the game accepts "dad" as a valid synonym for "Frank" without comment. This implies that Jeanie's attitude isn't related to the circumstances of Frank's marriage, but to some special dislike for him. The game allows her to believe that Frank is drunk even when we can later have Frank get a Coke. Her relationship with her mother seems to be better, but still distant; Jeanie gives the distinct impression of being uncomfortable spending time with her in the same room.
Jeanie is an interesting character, and her development through these indirect means is quite well done, but she doesn't manage to compel much beyond her status as a teenage-girl archetype. The danger with stories which withhold information about characters until late into play is that you risk underdeveloping them, or worse, telegraphing them by forcing too much development into a short time. Jeanie has a goal or two beyond simply going out, but what her motivations are for this are never explained to my satisfaction.
Teenagers are difficult characters to write well. Children, adults and the elderly are generally conscious of the roles society is asking them to play in a way teens are not. Transitioning from childhood to adulthood is a hellish process of comprehending things about yourself you may have never wanted to know; it's an experimental time of making light of things you should value, or taking too seriously things that will later prove embarrassing. Most of us carry some form of embarrassment or baggage from our teenage years, and the natural instinct is to translate this into unlikable, one-dimensional literary characters. The protagonist of "Where Are You Going", Connie, is a fascinating character because O'Connor reveals to us not only her basic character, but the tension between Connie as she presents herself and Connie as she "really" thinks herself to be - a social actor who revels in acting and disdains others who do the same. Jeanie doesn't get much of a chance to be likable, and nor is she given this kind of secondary dimension.
Frank and Deb, Jeanie's parents, are of a similar persuasion: while they are presented well in their basic forms - the harried housewife and the under-appreciated husband - they aren't much developed beyond these things. Frank thinks in passing about how he loves Jeanie but sometimes feels like spanking her for being a brat; but the game never asks him or the audience to think further about this. Deb's personality is conveyed more through very light puzzles - I'd call them "frustrations" - but again, we're not shown how she generally addresses her frustrations with Frank and Jeanie.
The thing is that there's nothing obviously wrong with the writing; and while the characters don't exist much outside of their archetypes, you can still use archetypal characters to write a good story. I had to think for a bit about what really bugged me about them before I realized it.
I'm fond of saying that narrative is about setup and payoff. In this instance, the better term would be "conflict and resolution".
"Where Are You Going" isn't just a portrait of Connie, it's a shattering of Connie's world. Her interactions with Arnold Friend, the antagonist, are at least as fascinating as Connie herself; Friend is a creature from the edge of Connie's comfortable reality, a man who cannot be manipulated by adolescent "performances" the way the other drooling boys can. Connie's encounter with Friend slowly strips away her sense of security in her presented character. In other words, O'Connor is doing more than telling us who Connie is: she's throwing obstacles in the path of Connie's existence and telling us something about how Connie navigates (or fails to navigate) them.
Jeanie, by comparison, never really encounters obstacles. There are a couple of very minor inconveniences that slow her down, sure, but at no point is she really in danger of failing in her goals. We see who she is, she does what she does, and that's it. There's no conflict. Common Ground lacks it, and as result it lacks drive, it lacks thrust. It is content to present its characters without really challenging them.
As a result, while hardly an incompetent work, Common Ground never attains the edge it might otherwise have had as an IF short story.
(P.S. The comparison to "Where Are You Going, Where Have You Been?" isn't because I particularly think the author was influenced by O'Connor; it's more that I found O'Connor's story instructive in examining the flaws of Common Ground.)
Play it if: you're in the mood for two hours inside the head of a resourceful, self-aware infant, concocting and enacting daring plots to get what you want.
Don't play it if: you want something more narratively substantial, or you have a hair-trigger pet-peeve for anything to do with kids.
I've had a running idea in my head about a work of IF based around a robot protagonist who wakes up in a state of semi-assembly, and has to work to complete itself while having to work around its inability to carry out certain very basic tasks. I mention this because Child's Play is basically a complete fleshing-out of that idea, with the difference being that the half-formed PC is a human rather than a robot.
The challenge and fascination of the game is that the PC's goals are entirely straightforward and achievable for most human beings (i.e. retrieving a toy and playing with it), but require significant effort and lateral thinking for the PC here. The puzzles are surprisingly tough and complex given the limited range of actions the PC can take, but that sort of demonstrates the ingenuity of the game: it's all about milking your few reliable skills for as much as they're worth, and manipulating others to do the things outside your own capabilities. Even though they draw on the same basic principles, the puzzles never feel repetitive or boring, though I suspect that with this game Granade may have exhausted most of IF's potential for games based around plausible baby-behavior.
Plausible baby-behavior is another notable thing. The writing of the parents and the babies betrays significant personal experience with both. The children are believable in their free-form, goal-oriented behavior - most of the time, just living in the moment according to what their personalities dictate, and occasionally acting in the service of some higher agenda - and even more so in their elicitation of parental responses.
The PC is a touch more self-aware and wise than one might expect an eleven-year-old to be, but it was clearly intentional and it adds a neat humorous dimension to the story (with the PC taking pride in his/her age and refusing to commit certain acts as being "unseemly" for such an age category). As with other good examples of prominently-featured narrative voices such as Lost Pig, For a Change, and Counterfeit Monkey, the novelty doesn't outstay its welcome but takes a step back and lets the exploration and challenge of the game take center stage.
This is normally where I would butt in with some discussion of the less positive aspects of the work. But the truth is that I can't see any holes in Child's Play. The author's commentary might have worked better as a running part of the description rather than requiring a separate command for each note, but it would be absurd to count that as a flaw. The game is simply a good, fruitful concept fully fleshed out and executed with wit and polish. This is the kind of short game I think most IF writers want to publish at least once in their lives, and Granade should be very proud of it. Highly recommended.