Edit: Game is done! Check this post for more details and a play link.
I've been thinking about this all afternoon, and what's bubbled to the fore in my head is a game structured around a philosophical conversation about whether or not a given act was just. The player assumes the role of a party intimately connected to the event in question, and predisposed to bias in one direction, and the CPU interlocutor will take an opposed tack. Sort of a riff on the Turing Test, really, but with a narrow scope.
Originally I thought about using an old Infocom-style parser, but then I realised those were a pain and were better suited to input of the form "look door" and "go north" than the full sentences I'm hoping for. So I thought about using a more modern dialogue menu, but that seems too constrained and mechanical; if this works at all, I expect the fun part to be in how you can say whatever you want to say. So I've decided to do a hybridisation of the two ideas, and have the player select a "tone" from a list of choices (happy, sad, angry, e.g.) and then type an actual response into a text field, which will then be parsed alongside the tone. The game will then (ideally) formulate an appropriate response.
The conversation will be structured in "acts," so to speak, though not rigidly; I expect player input can alter the length and the order of things. Also I'm attempting to avoid establishing one set of conditions that must be met in order for the player to win; that turns it into a sort of glorified game of twenty questions, which is not what I'm after at all. I'd rather keep it open-ended.
The format will probably be text-only, and I'll most likely write it in PHP, since that suits both my programming and artistic skillsets, while also, I think, suiting the game nicely. The focus is on the exchange of dialogue, and I think adding much in the way of graphics or sound would detract from that.