Below is a wiki post (meaning you are welcome to edit, and encouraged to add more) outlining mechanisms used within tabletop adventure games, in the style of Building Blocks to Tabletop Game Design. Mechanisms should have an example game from which they appear, an explanation of it, and if possible - editorializing and theorizing about the mechanisms implications in games and future designs.
Base Definitions
- Aesthetics: The emotional response players have to the dynamics created by interacting with the mechanisms of a game.
- DFK: Drama, Fortune, Karma - a mechanism categorization proposed by Jonathan Tweet in the game Everway that describes the fundamental resolution method behind any mechanism.
- Drama: Any mechanism that is ultimately resolved via fiat related to whatever is most “dramatically” or narrative-appropriate.
- Dynamics: The patters and behaviors that emerge when players interact with the mechanisms of a game. For example - in early editions of classic D&D weapon damage is approximately equal to character health, so it is common in those games for players to look to avoid direct combat, or stake the odds in their favor to circumvent this.
- Fiat: A method of resolving dependent on a party (typically the referee) making a decision.
- Fortune: Any mechanism that is ultimately resolved with a randomizer, such as dice or cards.
- Karma: Any mechanism that is ultimately resolved by a comparison to some value, be it static (such as statistic vs. statistic), or dynamic (such as whoever spends the most Hero Points).
- Mechanism: The base rules and ludemes of a game.
- System: Any method the participants of a game use to determine what is going on within the fiction, including but not exclusive to the rules text.
- Technique: The actual rituals and practices governing implementing mechanisms and the use cases around them. Speaking in-character vs. third person narration of a summary of what a character says are examples of two techniques, as is how as table decides a situation is “difficult” and requires a roll, etc.
Advantage/Disadvantage
References
Barbarians of Lemuria, Dungeons & Dragons 5th Edition, Call of Cthulhu 7th Edition, about a million other games
Summary
The notion of advantage and disadvantage comes in a variety of forms, and under a myriad of terms, but at its most basic, it entails making two separate rolls and then selecting the best roll in the case of advantage, or the worst for disadvantage. Some systems that utilize d% systems will often only use an additional d10, as that tends to be the dominating factor, and once and a while a dice pool system will simply add in an additional die, and then remove either the best or worst replacement, respectively.
TODO: insert link to blog post breaking down math on D&D5e advantage when I remember where it is.
Advantages are handed out for a variety of reasons - typically if the character has special training or an additional feat, if they are able to take additional time and care to their task, if they have some especially beneficial equipment, aid, or the situational conditions just favor them. The reverse is also true for disadvantage. This can be a very easy way to provide bonuses or negatives to fictional situations if the referee does not like having to estimate specific degrees of modifiers (such as determining that help from another individual is a +1 but really good tools are +2, etc.)
Considerations
One of the biggest impetus for using something like advantage is that it couples a relatively quick handling time, as players are using at least one less mathematical operation by leveraging an additional roll, and it plays into the sensation aesthetic of getting to roll more dice.
A potential downside when considering this mechanism, is that the math is not necessarily linear, and how much of a benefit or disadvantage is being received will be relatively opaque to most players. Games such as D&D5e attempt to circumnavigate this issue by utilizing “bounded accuracy,” but you still have non-obvious disparity between a target number very close to your skill level, and one very far.
The consideration of “how many” advantages and disadvantages may stack should also be considered, as in most systems even two advantages will HEAVILY skew towards success. Many games will limit advantage/disadvantage to a net total of one, due to this case. None the less, it may be worthwhile to allow multiple stacks for the joy of lots of dice, or simply if you want to encourage hunting for advantages.
Hit-points (hp)
References
Dungeons & Dragons, GURPS, Basic Roleplaying, many more
Summary
Hit-points in adventure games represent a variety of concepts that almost all eventually describe how far from death or being disable an individual is in a combat scenario. They are strongly associated with, although not exclusively so, to health.
During a game of Blackmoor ran by Arneson, Bob Meyer was playing a character who Arneson had described as a “hero.” In this game, Meyer’s character confronted a troll, and after failing to strike the creature several times, the troll clubs Meyer’s hero, killing him immediately. Meyer and Arneson convened on the game, and decided that the “hit dice” mechanism inherited from Chainmail did not adequetly match up with the play expectations Arneson had conveyed to Meyer. Arneson adapted rules from a civil war naval game The Ironclads, importing an abstract representation of resistance to death in the form of hit-points. He noted this was more successful in D&D than in many large-scale wargames, as you only had to track the hit-points of one character rather than a whole fleet of ships.
Gygax was later noted within the Advanced Dungeons & Dragons Dungeon Master’s Guide that hit-points serve to represent something akin to narrative importance, stating that in Errol Flynn’s Robin Hood, the mooks were easily dispatched, but Robin and the Sherrif both had significantly more hit-points due to their importance in the tale.
Dungeons & Dragon’s tends to treat hit-points are purely abstract - they are values whose losses and gain can represent whatever is needed in the fiction. If a character looses hit-points due to being struck in combat, this could just be them parrying blows and getting fatigued, or it could be them stumbling on their backfoot, twisting an ankle, or some other appropriate consequence.
Outside of Dungeons & Dragons, games tend to waffle on what exactly hit-points represent, a debate that often gets commented on as “meat points” - a term for when a game has a direct correlation between actual physical harm and hit-point loss. Many games take a kind of midway point between abstraction and meat-points - games like GURPS or Basic Roleplay allows for small losses of hp, or losses up to a specific threshold to be abstract, but beyond that spurs on actual physical consequence.
Hit-points are one of the biggest legacies of role-playing and wargaming mechanisms, having shown up in video games, lit rpg fiction, and pop-culture, so much so it can be difficult to get gamers to conceptualize alternative models.
Considerations
When implementing hit-points in a game, one should decide just how abstract or specific they are, in addition to what other systems interact with them. For example, in old-school Dungeons & Dragons, having low hit-points tends to not affect a character, but a few monsters have abilities that end up keying off of hit-points, such as dragon breath. In 4th edition Dungeons & Dragons, being below half hit-points would specifically tag a character with a status effect, allowing certain abilities to affect them differently, and in some post-4e games “boss monsters” unlock varying abilities at differing stages of hit-points.
Consider elements that may conflate your model of hit-points, if being used. Its a common note in old-school D&D that hit-points aren’t injury, but the spell that returns hit-points is “Cure Light Wounds,” confounding that statement.
Also be thoughtful of such things as damage scaling and hit-point growth (if hit-points grow in your system).
X-in-6
References
Original Dungeons & Dragons, Basic Dungeons & Dragons, EZD6
Summary
Traditionally used throughout D&D to determine outcomes such as actively and passively searching for secret-doors, listening for sound beyond a door, breaking down a door (see the oft-posted “D&D is a game about interacting with doors” meme), as well as determining such things as chance of surprise, this resolution method is also suggested as a general case ruling for referees to use for situations they either don’t know the outcome to, or prefer to divest responsibility to the dice.
This mechanism is roughly equivalent with any other resolution method that assigns some probability to an outcome, and then transposes that outcome onto dice. It’s likely that the six-sided die was used in D&D out of availability.
Based on anecdotes around games such as Braunstein, this is likely the second ever ttrpg mechanism used, after referee fiat.
Considerations
Often the X-in-6 method is statically assigned contextual to the situation, without much involvement in things such as modifiers (it is generally assumed such “modifiers” are worked into the referee or suggesting party’s determination of probability). Sometimes there are situations that modify this, such as being an Elf or not when searching.
Benefits to this mechanism include that it is extremely straight-forward, often very easy for players to determine the probability of an outcome, and a referee doesn’t have too much of a range of outcomes to consider (the results are usually binary, but there is nothing to keep a referee from ruling based on the specific roll and how close or far it is from the target). The steps are also linear, which makes predicting probability generally easier for participants.
The fact that there is so little gradation between percentages on a d6 die can be seen as a downside, especially if one is going to be adding modifiers or allowing the addition of attributes to afect the rolls. This can be negated by stepping up the die type, likely to a d%, as was mostly done in games such as Advanced Dungeons & Dragons.