I've mentioned briefly on twitter my attempt to write a game or two in the "Visual Novel" format . It's an easier to write genre than IF, as much as I love IF, and a more interesting genre than just a CYOA. The art requirements are generally a bit kinder if I try to explain them to any interested artists than the traditional adventure game (fewer animations, no walk cycles, ...).
I've smashed this in with my desire to play with writing Mass Effect-like 2D conversations. I realized that a single 2D "compass" menu makes a lot of sense as the driving focus for a Visual Novel game. In particular, it gives more of an IF-like "map directions" relationship to locations, albeit with an even more visual Pie menu chooser.
I think its safe to announce the engine I've been writing, the Keystone Literary Menu Pie (abbrev. KeyLimePie), named of course for the Pie Menu that is the keystone in the engine. If anyone is actually interested, I am planning to release it as Open Source as it comes closer to completion (which should be soon, I expect). I'm focussing on cross-platform, browser-based Silverlight (with IronPython magic!) for the main player engine, which means I will be testing it in Moonlight as well (but I don't expect any difficulties; Moonlight rocks). I've also been building some editing/development tools against normal CPython. (It will be easy to port the engine to non-Silverlight platforms, which are in my mind primarily iPhone and Android. I could see writing a pygame engine as an excuse to better learn pygame, and because that would also be really easy.)
(I guess I should note that I'm not actually announcing any games that I'll be writing for it. I haven't decided on a "real" game to write yet, and the test game I've been writing is possibly controversial and I've not quite figured out if it is that "good kind of controversial" yet.)
All of which is but one preface to my present topic, but let me first make a quick tangent into a second preface. Forgive me if it comes off as a bit of a rant. As a result of my job search I've been presented with a small handful of programming "tests". I would argue that programming is something that is hard to test at a distance, but more critically that a good majority of these tests that I've seen (and definitely the majority of ones I feel like I've "failed") tend to often favor the programmer with Asperger's and a compulsion to brute force the 80% answer as quickly as possible.
It's very obvious, to me, that I can't compete with that, and that it is fairly clear to me that these tests are almost intentionally designed as something of an affront to programmers like me. The general pattern is that the test gives a time limit and a problem with a couple of example test cases. The assumed response is that you write enough code to "solve" the given test cases (and not much more), and as far as I can tell that is the only way to get anything finished in the given time limits.
The graduate student that I am takes a look at the problem definition, says "Oh, that problem is NP-Complete, but there are known algorithmic solutions that get reasonable performance," and then goes off to research those until the time expires, with not much in the way of finished code to show off, but a better understanding of the original problem statement than perhaps the test writer ever had...
Software Engineering as a whole, across the board, is rife with just a common failure to research. There are unspoken, sometimes unnoticed, tendencies to build "quick and easy" 80% solutions that brute force a given problem set, without examining if there is a well known generic solution or even bothering to think through the remain 20% of edge cases. Coupled with NIH syndrome ("Not Invented Here", where teams seem to only trust code they themselves have written) and an odd confusion between complexity and "power" or "ability", and sometimes it is a wonder that good software ever gets written.
Sometimes it is easy, or so it seems, to forget to work smarter, not harder.
So, back to the topic at hand, for KeyLimePie I wanted it to be easy to create conversation scripts. That's what it is all about, sure. I looked at ChoiceScript for a nearby example, although it certainly doesn't have the sorts of tools that I was looking for it was nice to see someone else's approach.
Now, both approaches will have their admirers, but I ended up going in a different direction for several reasons. One thing that was important to me was to reuse existing parsers. Now, I like writing parsers, and I certainly have the chops to build powerful parsers, but I try to find the right tool for the job. In the KeyLimePie conversations I wanted to focus first on the declarative nature of the conversation flow, which meant a markup language of one sort or another, and less on the scripting of it. In this case I decided upon YAML as the framing system, which I think looks like a reasonable approximation of a conversation script (as in a play script).
There's another benefit to using a declarative markup language as the framing document, which is rich editing tools. In fact, I researched diagram tools for that purpose. However, I didn't find any I particularly liked for the purpose of KeyLimePie. I did find a few programmable components that would have worked, but all had triple-digit single-developer license fees. That'll be something to consider for the budget if someone wants to help pay me for a "Visual KeyLimePie" designer or if I go to Kickstarter or somewhere to fund an actual game with an intent to publish it. On the other hand, I do know Graphviz fairly well by now and so I do already have an after-its-written visualization tool for the conversation scripts. (I'll probably attach visualizations to future posts, if I continue to write blog posts about KeyLimePie.)
One thing I was having an imaginary debate with myself about was flow control. Something I think a lot of people don't learn from the abstractions presented in an Automata theory course (and don't get me started on the programmers that never take one) is how simple a scripting language can be, and yet still provide very complex possibilities. For example, its very easy to take any of those useless "calculator" exercises that every textbook and professor uses to teach a Grammars/Compilers course, and add simple lambda expressions to the grammar and interpreter. Given the lambda support you have instant "full" scripting language for real computation .
The scripting in KeyLimePie, thus far, is limited to the descriptive flow of your basic Finite State Machine diagram . There's descriptive arrows from one conversation node to another (admittedly a fine line distinction from an imperative goto, but for obvious reasons of abstraction level), and there are optional pre-conditions that can be added to those arrows, via the cond field (a lispish abbreviation for a lispish data structure, I'll admit ). Nodes can have optional post-effects, which can affect which pre-conditions apply, but that's about it. 
The sequence of pre-conditions creates an implied if/else structure (or switch/case if you prefer, but whatever) and so my imaginary debate wondered if I should provide more "programming language forms" for it. So far I've decided for the simplicity of the current declarative model and against more imperative-like flow control.
All of this will probably make more sense in context of some examples, which I'll save for another post, and the script format documentation itself.
|||Visual Novels are primarily a Japanese adventure game cousin that are often not much more than heavily illustrated Choose-Your-Own-Adventure (CYOA) books as videogame. They generally use reusable backdrops and simple character sprites, with a focus on one-on-one interactions between characters and a simple menu-based inferface. The easiest examples that can be found in North America is the fun Ace Attorney series (aka the Pheonix Wright series). There's also the Harvey Birdman: Attorney At Law videogame, for the more (im)mature audience.|
|||Admittedly the performance may not be the greatest. Certainly it a lot tougher to implement the tail recursion you might need to get great performance for real applications. The point stands, though, that the distance between "toy calculator" and "real programming language" is smaller than most people realize.|
|||I'm not in the mood to explain that. It's something that a good Automata course should have drilled into one's head. The full math description for the autistic at Wikipedia may suffice as a refresher, but there are easier ways to teach it.|
|||Not to belabor the point that I'm extremely underemployed or anything, but I spent a whole semester of school writing primarily Common Lisp, and sometimes I do realize that it was a very good exercise to have done that.|
|||Incidentally, just as I decided on YAML to avoid creating my own formatting/special language, both cond and effect are themselves embedded Python, right now, because I didn't want to invent a magic mini-language, and because I can easily embed Python expressions and statements in both Silverlight and CPython. You could use "real Python" to do some crazy stuff, probably, between the two fields, if you absolutely miss your imperative coding paradigms, but I don't expect most people to use it for anything more than basic variable manipulation.|