About previous knowledge assumption (and an equation)

I’m considering a puzzle regarding a physics problem.

One implementation hypothesis is to “drop” a physics book in the game, which literally teaches the player the physics of the problem. Another hypothesis is to not do that, and assume the player either knows the physics of the problem, or goes outside the game to study it.

The second one adds to the challenge, but if the player doesn’t know his physics and goes to the outside world for information, then I get this feeling I’m disrupting something in the suspension of disbelief, since the PC itself “cannot leave” the game world to study.

I, therefore, come before you for advice.

My second existential doubt regards an equation. This physics problem will have one to solve, which will involve a simple division operation. Here I have two choices: either to assume the player will use his own calculator to get the result; or to implement an ingame calculator. What are your thoughts? Is it acceptable to ask the player to use an out of the game item?

Unless you’re deliberately shooting for a gap in player/character knowledge (which might work if you’re making a learning game, for example), you should probably let them learn things in-game. I kind of like the idea of the player being able to use a high-level command like “> divide 12345 by 78” to receive an answer like (depending on the setting) “You whip out a scroll and a quill, and determine that [n] divided by [m] is [n/m]” or “You punch the equation into your trusty calculator: [n/m]” or “You do the math in your head: [n/m].” That might minimize the fiddling about with buttons that fully implementing a calculator might require, and if you do something like the middle one, you can just redirect anything having to do with the calculator to “You can use it to ADD, SUBTRACT, DIVIDE, or MULTIPLY.”

For the book dropping, does it make sense with the pacing of puzzle to give the player control over whether or not the book drops? That way, if they already know the physics, they can feel clever, but anyone else (or anyone who wants to make sure in-game physics are the same as in the real world) can experiment with the book first.

Yape, I’m more inclined to implementing some sort of calculator. I’ll try to think of a natural way to word it.

The game will have an NPC to help the player around, so, as for the book, you just gave me an idea: I can have the NPC give it to the player, if he asks.


Heh, it would be interesting to be able to type in “12345/78” at the command prompt. Sure it could be done, in I7 at least.

As to the first issue, I think it depends on the level of of physics knowledge required. I have no problem with a game that requires basic “common-sense” knowledge of how the world works and even a basic level of education; thus, I would be quite happy if the game requires you to know that if you fall asleep under an apple tree an apple might fall on your head. On the other hand, if the level of knowledge is closer to understanding Einstein’s general relativity (which I probably wouldn’t understand anyway even if you built a textbook into the game), better to build it in than to require the player to do research external to the game.

As far as calculation is concerned, if we’re talking basic arithmetic, people ought to be able to do it without the need for electronic assistance (and if somebody really does need a calculator they can use their own). If you’re talking about a level of math that goes beyond adding, subtracting, multiplying and dividing, you may be limiting your class of potential players. That’s true even if you build in a calculator; people would still need to understand the math well enough to use the calculator, and that pretty much eliminates a lot of people (I’m one of them).

Robert Rothman

Just a technical note on all this: I7 isn’t going to be able to parse something like “divide 20 by 4” out of the box, because you are limited to one value when defining a command’s grammar. There are ways around this, though, such as parsing commands containing “divide” iteratively to grab second, third, or more values. Here are some links to discussions about matching more objects and texts (a kind of value) than Inform normally allows:

groups.google.com/group/rec.arts … 61b9823115
groups.google.com/group/rec.arts … b1dadc372f

None of these will do just what you’re looking for, but the code examples should give you some ideas.


I’ve always wanted to play with a slide rule, but I’ve never had a chance. This would be a great opportunity to make a virtual one!


When I was in high school, we actually did have to use slide rules. I remember when the very first electronic calculators (as distinct from the old mechanical adding machines) came out. They cost about $400 (that’s in early 1970’s dollars) and could actually do square roots as well as the four basic arithmetic operations.

Robert Rothman

In my SPAG specifics analysis of Rendition, I wrote:

What I was getting at is that there is no reason to limit the puzzle world to the game world, and not doing so opens many possibilities. Look up physics on Wikipedia? Sure!

Now, if you want to have the player “get into” the game and “suspend disbelief”, you should avoid such out-of-game tricks. But although mimesis and suspension of disbelief can be good things for a game to aim at, they are not good things for all games to aim at; they don’t have to be among your design goals. Whether they should be for this particular game is something you’ll have to decide for yourself, of course.

If you did instruct your player to look at outside sources, how would you cloak those instructions in-game without breaking mimesis? If you just have an out-of-game [try wikipedia] message, that just seems lazy and the player wouldn’t return.

Secondly, imagine sending a player to TVtropes.com or something. They might get stuck there and never return!

The calculator I could see having fun with. Make the in-game one, but make it real easy to lose or never get it. You could have some meta-fun along the lines of an unwinnable-game scenario because you (the player) can’t divide, so will never solve this puzzle!

Come to think of it, that might work for my first question.

Oh, I also think a distinction needs be drawn between sending players to outside sources of in-fiction material – like a character’s Facebook page, which works like Shadow Unit have done successfully – and outside sources of outside-fiction material, such as textbook physics.

Then again, Vorple might render this hand-wringing moot.

In Yon Astounding Castle! of Some Sort, there’s a riddling gnome who asks you two easy questions, followed by a third that’s obscure enough that you were obviously expected to look it up. Lots of reviewers hated this, but I thought it was hilarious, kind of like the Hitchhiker’s Guide-style puzzles mentioned here (the actual puzzle is from Adventure, for which, spoilers). Except, since it was pretty easy to look up, it wasn’t unfair in a way that stopped my progress in the game. But YAC!oSS goes to a lot of work to establish that some of the time it’s basically trolling the player (for instance the business with the


), and anyway a lot of people didn’t like it. And if I had been playing on a train (where I wouldn’t have internet), it would’ve been annoying.

There’s a similar thing in Reliques of Tolti-Aph – you can get some hintlike things from your journal, but the pages of the journal are numbered according to the stars in some constellation, so you have to look that constellation up on Wikipedia in order to read your own journal. (There’s actually a feelie that mentions all the relevant stars, I think, but it’s pretty well buried.) This did not amuse me as much.

I actually found it interesting to break or manipulate this fourth wall. I sometimes do it with this WIP of mine, but I still don’t know if I want to in this particular detail. Giving the tone of it, it wouldn’t be hard, though. And a devilish calculator does sound… devilish :slight_smile:

Gijsbers ideas are also compelling. They’re great for a team IF effort of sorts, in which multiple authors are responsible for multiple parts, like one for the facebook page, one for the blog, et cetera.

I have a friend who says that a work that nobody hates isn’t a worthy one :wink:

I’ve kind of grown to like the Infocom tradition of putting hints in the feelies. Although originally intended for copy-protection, it makes the game world feel a little bigger (though I usually forget to look things up in the feelies unless it’s obvious that I need to - minor spoiler for Sorceror - e.g. the yipples).

It seems reasonable in a modern-day game that feelies could be available online, and might not even be created by the author. Sufficient introduction to the game might give the player enough warning that they could download the relevant information before actually encountering the puzzle. For example, a feelie or bit of introductory text could mention something obscure without giving an explanation of what it is, perhaps assuming that the PC already knows about it. I think that could be done in a way that would encourage research. Later in the game it would not seem so fair.

There’s also a wealth of information that is easily available in places other than the Internet. An old game called “The Golden Wombat of Destiny” contains a clue in the form of a Shakespeare quote. I didn’t have regular internet access at the time, but I did happen to have the complete works of Shakespeare in the house, so it seemed fair and it was fun to look up. The play, act, and scene were mentioned in the quote, so no fancy searching was necessary.

Amen. My current megaWIP (not to be confused with all the little WIP whelps yapping at its heels) takes this approach shamelessly (ToaSK only flirted near it without crossing the line). Constructing the feelies is a big part of the work and a big part of the fun, and while I appreciate the idea of a “completely self-contained” file, I’m content with that file being the ZIP the whole package is bundled in :slight_smile:

I agree, and echo what an earlier poster said about “mimesis:” if your goal is total, constant immersion, then obviously you’ll want to avoid making a game where most players will need to break out and go do some reading. But immersion isn’t the be-all-end-all, and real-world out-of-game “feelies” and virtual scavenger-hunting for facts sounds like a rip-roaring time to me. I’d be very eager for such a game.

This whole discussion reminds me of that game, “In Memoriam”.


A glorified collection of flash minigames, but with a lot a cool out-of-game gimmicks, specifically designed to blur the line between game-world and real-world. Playing through it was exciting, until the simple structure of the game became painfully clear.

To me there is a major difference between information which is necessary to complete the game and that which is merely tangential. When it comes to things which are essential to the game and which go beyond what a reasonably educated person might be expected to know (taking into account the fact that there could be cultural differences in what is “common knowledge”), I would not want, as a player, to have to do actual extra-game research. (Feelies are fine; I view them as part of the “game world” nothwithstanding that they are provided in a different form).

On the other hand, I have no problem whatsoever with allusions which might enhance the game experience or provide an additional chuckle to those who are “in the know,” as long as they are not crucial to successful completion of the game.

I wrote a game based on certain characters from popular culture (or at least the popular culture of a few decades ago). In order to get through the game, you have to have a basic idea of who those characters are and how they behave, but you don’t need detailed knowledge of their work. If you happen to have that detailed knowledge, you will understand a lot of references and allusions that would go right by somebody without that background, but you can still play the game. I also have a place (which the player encounters quite early in the game) where he is referred to a couple of sources (outside the game world) for learning more about the characters if he wants to, but doing so is purely optional.

One exception to the notion that no extra-game knowledge beyond common knowledge should be required is where a game is aimed towards a specific audience who would be expected to have that additional knowledge (or, to put it another way, the notion of what knowledge is “common” might be viewed with the intended audience in mind). To take an example, let’s say you’re writing a game set in the world of modern popular music. Players who would be attracted to such a game would likely have a certain amount of knowledge (e.g., the names of performers or songs) that somebody like me would not likely possess. I’m fine with assuming such knowledge, as long as the nature of the game is clear. If I see such a game, I’ll probably pass it up on the theory that it is set in a world which does not appeal to me. On the other hand, if the game appears to be set in the world of jazz (which would attract my interest) and then turns out to require extra-game knowledge of rock songs, I would be very disappointed indeed.

Robert Rothman

This can backfire. My Comp entry (in 2009) had a title that was intended as a mildly punnish allusion, which tied the central puzzle to the setting. (Slightly more specific information: If you knew what the title meant, it might give you a clue that Something Was Up, but certainly not exactly what, and in fact too literal an interpretation of the title could be considered a red herring. Additionally, the title and theme were chosen after the central mechanic was solidified and coded, and after the first round of puzzle-testers.) So the review that I was saddest to read – unlike the reviews that simply hated the game, thought it was unfair because of the sneaky presentation of the puzzle, or found bugs, which were of course a bit unfun to read, but did not actually make me sad – was the review that stated that the game was unfair because the puzzle was downright unsolvable without knowledge of the allusion. Sure, the game had some intentional unfairness (in the way that I presented the puzzle, particularly in the Comp context), but this particular review thought I was being unfair in a way that I did not at all intend, or even think could possibly be a problem. As far as I knew, none of my testers caught the reference and they solved the puzzle just fine. So it’s possible that just knowing there’s an allusion at all is enough to make players that weren’t “in the know” feel left out.

Yeah, that confused me. I was like, “I looked up the allusion, and it didn’t help me solve the puzzle one bit.”

Actually, it was done, long ago, in Tads 2: +=3.

~ Neuro, still unconvinced. :wink: