Why?
When the subject of Solo RPGs comes up, one of the first questions asked (besides why) is how? Stories, story games, and RPGs all involve some sense of exploration and mystery solving. How do you play a game like that when you are the one creating it and thus know everything before you begin?
Good question. The simplest response would be: through the use of an oracle.
It turns out, that using an oracle is not really that much different than how a regular game is run. Sure, a bad GM will construct a plot and then railroad the players into following it regardless of player "choices." A competent GM will usually have some sort of plot or plot elements ready but understands that (as the much-paraphrased saying goes) no plan survives first contact with the enemy and so is prepared to wing it when the players inevitably head off in unexpected directions. Experienced GMs frequently don't even prepare a plot. They'll just lay the toys out for the players, read their reactions, and push plot elements in front of them as appropriate--rather like a jazz player riffing on narrative rather than musical themes.
I'm sure that many players have posed a question to their GM for which they were entirely unprepared. More then once I've seen (and done this as well) a GM quickly assign probabilities for various outcomes in their head then roll a dice to determine what actually happens. This is no different than what happens in Solo play. In fact, when you consider that both the GM and the players are responding to ideas randomly generated by the other, it really is no different than if dice had determined both the setup and results of a player's actions. (And I've had some pretty random players.)
So what is an Oracle and how do you use it?
An "Oracle" is a simple tool or method that a solo player uses to help him determine the results of a narrative question. In its simplest form, it can just be tossing a coin and calling out heads or tails or rolling a die and calling odds or evens. It helps the player make a decision when they truly have no idea how to respond and it helps them avoid common repetitive responses, injecting a certain sense of surprise and uncertainty to the game/story.
More complex versions can provide additional information. Usually, these are fairly generic Magic 8 Ball kind of responses that have to be interpreted within the context of the game events to determine the outcome. (Presumably this is how it got the name "oracle") Just as how early RPGs went from simple binary "hit" or "miss" results on character action rolls to a more graduated series of responses (including critical success/failure or partial success/failure) the most common oracles take a clue from improv theater and--in addition to a simple yes/no--introduce the concepts of yes/no and... or yes/no but...
In practice, these tools are little different than the random encounter tables, NPC reaction tables, or critical hit tables used in traditional RPGs. The oracle tables are simply a more generalized form that allows their use in a broader range of situations. Considering their similarities, you could argue that RPGs have always included an oracle in some form as a part of the game.
An Example: The MOODPIGS Oracle
Above, I've included the oracle for the solo adaptation of MOODPIGS on which I am working. The normal resolution system for MOODPIGS is a comparison of the results of opposing dice pools. The dice pool's size will generally start within a range of 1-6 dice and may increase by adding an additional 1-3 dice and/or by re-rolling dice. An "average" value--such as might be used in a situation where no particular skills or situational modifiers apply--is 2 dice. The player would roll his 2 Action Dice (labeled AD in the table above) for his character's actions, while the GM (or sometimes the player himself) rolls the Challenge Dice. (CD in the table above) Simply compare the AD and CD results to the Oracle table to determine the outcome.
Breaking Ties and keeping the story moving.
Some game resolution systems--including MOODPIGS--allow for the possibility of a tie. This is problematic as an answer to a yes/no question. In fact, depending on the relative size of the competing dice pools, the chance of a tie can rise as high as 33%. While some degree of ambiguity may be appropriate for anything that gives at least some pretense of following reality, nothing is more annoying than repeatedly being told to try again. As a result, 2 of the 3 possible tie results have been given slightly different interpretations so that the story can move forward even if the story's character doesn't. In addition to the ambiguous Yes...and No, there is Interruption/New Event which means that before you can even find out the answer to your question a new situation has taken over and must be dealt with. And... (taking a clue from the Recluse Solo Engine) there is Question Assumptions, which means that the question itself is based on a misunderstanding. Something that is assumed to be true (or false) isn't and you need to re-examine what you think you know.
Interpreting the Results
- Yes, And — The answer is not only yes, but the results are even
more yes than expected.
- Yes, But — The
answer is yes, but only mostly yes. The results are compromised.
- Question Assumptions
— The question is based on a false assumption. Reconsider something
assumed as true.
- Yes — Keep going
based on this fact being true.
- Yes… And No — Or
neither. The results are ambiguous, or the task is bigger than expect. Additional requirements must be met or a different approach tried.
- No, But — some
aspect may be true or some path might be found to the desired
outcome.
- Interruption / New
Event — Something new and unexpected and probably urgent has come
up.
- No — Consequences
may follow.
- No, And — Not only
no, but worse than no.
The oracle presented here--and indeed as most oracles are--is evenly balanced between yes and no responses. Sometimes the player may wish to weigh the answers a little more heavily toward the yes or the no while still allowing for the possibility of either reply. This can be done by simply rolling extra dice but counting only 2 of them (the 2 highest or 2 lowest depending on which way you want to eight them) or by rerolling 1 of the 2 dice if one of them happened to not be counted.
An Example
A character is attempting a task that is not particularly likely to succeed, but which could be very helpful if it does. This task does not fall into any of the normal skill categories so the player decides to use a standard 2 Action Dice vs 2 Challenge Dice roll but to give the Challenge Dice a bonus to indicate the increased difficulty of succeeding. The player has already determined that only even-numbered results (e.g. 2,4,6) will be counted as passing. Odd results (1,3,5) will not be counted. The player has 2 options.
Option 1: The player rolls 2AD vs 3CD but if all 3 CD come up as even, he only counts the results as 2.
Option 2: The player rolls 2AD vs 2CD, but if 1 or more CD come up as odd, he may reroll one of them.
The end result is the same either way. It is simply a matter of preference as to whether one wants to roll more dice or make more rolls.
As you can see from the chart above, using 2D vs 2D gives an even chance of success, failure or a mixed result. By adding 1 dice to 1 side, the odds of 1 outcome happening increases from 33% to 44%. Adding 2 dice bumps it up even further to 58.33%. You can add even more, but once the ratio passes 2:1 you might as well just determine the results outright.