The Core Resolution Mechanic is used in any task resolution in a game that uses System X. It is also known as the Task Resolution System.
System X utilizes a roll chart system to translate the roll of one twenty-sided die and a Skill Value into a degree of success or failure (success margins). This degree of success or failure ranges from –5 to +5, with a critical failure and success as well. Unless otherwise modified, any positive margin denotes the success of a task, while any negative margin denotes the failure of a task. The critical success and critical failure results may be treated by any non-System X compliant game in any manner desired. A System X compliant game must, in its interpretation rules, define a critical success as a +10 value or an automatic success, and must also define a critical failure as a –10 value or an automatic failure. Automatic successes and failures derived from criticals in System X compliant games must be of a significant magnitude above and beyond any other success or failure.
A System X compliant game may choose to replace the "-" and "+" symbols in success margins with the letters "F" and "S," respectively. It must also allow both failure and success versions of the 0 margin.
A game that uses System X must not make any distinction between tasks and actions, which must be defined as any form of physical, mental, or spiritual activity that a player or gamemaster declares the associated character will undertake. Every task or action must coincide with the use of the core resolution mechanic unless the gamemaster, players, or intepretation or world rules agree that no roll is wanted or needed. A task or action may take as long to complete in game time as the gamemaster and/or players feel is reasonable, or as the game's interpretation or world rules may define.
In this document, all tasks or actions will be called tasks. It is recommended but optional that a game that uses System X choose one or the other term and use it consistently and exclusively throughout the text when referring to this construct. Games that are System X compliant or compatible must follow the above recommendation.
The use of the core resolution mechanic to evaluate the result of a task may be called a "skill check" or a "roll." These terms are interchangeable in System X compatible and compliant games.
A game that uses System X must use one (1) twenty-sided die in its task resolution system. This die must be in the form of an icosahedron. The die must be rolled only once per task, unless the game's interpretation rules optionally define a system-oriented reroll semantic. A game with a system-oriented reroll semantic is NOT System X compliant, but may be System X compatible.
A game that uses System X must use as inputs to the core resolution mechanic the roll of one (1) twenty-sided die and a Skill Value. In a System X compliant or compatible game, the Skill Value must range from 1 to 30. A System X compatible or compliant game must also define an interpretation rule that allows Skill Values outside this range, in which a Skill Value less than 1 always results in failure and a Skill Value greater than 30 always results in success. A System X compliant game must further dictate that any Skill Value less than 1 results in a critical failure, while any Skill Value greater than 30 results in a critical success.
System X compatible or compliant game must derive the Skill Value by adding together the character's appropriate, as determined by the game semantics or the GM, Skill and the Attribute that would be most appropriate, again determined by the game semantics or the GM, to the task. The game may allow free association of Attributes and Skills, or it may fix each Skill to a particular Attribute. If each Skill is fixed to a particular Attribute, in order to be System X compliant, the game must call the collection of Skills associated with an Attribute the Skill Pool of that Attribute. A System X compliant game may use Skill Value ratings that are not derived from a Skill and Attribute, but these must be restricted to tasks that are "special abilities" and are thus not otherwise implemented in the Skill system. This practice is not recommended.
A System X compliant game must use a 20 to 10 component bias, in which Attributes range from 1 to 20 and Skills range from 0 to 10. It may further require the "+" symbol to be placed in front of any Skill's rating. A System X compatible game, or a game that uses System X, may define any component bias.
The degree of success or failure is determined by cross-referencing the inputs (one (1) twenty-sided die and a Skill Value) to find the particular cell on the roll chart. The roll chart is a curvilinear statistical model of the interaction between the two input variables, with the degree of success or failure as the function output.
A game that is System X compatible or compliant must use the roll chart provided in this specification. A game that uses System X may alter the roll chart model as needed to reflect a particular bias towards success or failure.
In this roll chart, S-values are positive margins that reflect success. F-values are negative margins that reflect failure. CS stands for critical success, while CF stands for critical failure.
A System X compliant game must implement all of the following rules for exceptional situations in the core resolution mechanic.
All opposed rolls, which occur when two characters act to disrupt the progress of the other or in any situation that the game interpretation or world rules define, subtract the success margin of the target from the success margin of the actor. The result of this subtraction is the final success margin of the actor. In the case where the actor and target both roll a critical success, the final success margin is defined as +0. If both the actor and the target roll a critical failure, the final success margin is defined as –0. In all other situations, a critical result on the part of the actor is unaffected by the target's roll.
Assuming the actor does not roll a critical result, if the target critically succeeds, the actor's final success margin is defined as –0, regardless of his roll. Again assuming that the actor does not roll a critical result, if the target critically fails, the actor's final success margin is the result of his roll.
All combined skill checks, which occur when two or more characters work together to complete a task or in any situation that the game interpretation rules or world rules define, add the success margins of all actors together. If any actor rolls a critical success, the final success margin for the task is a critical success unless another actor rolls a critical failure, in which case the final success margin for the task is defined as +0. If any actor rolls a critical failure, the final success margin for the task is a critical failure unless another actor rolls a critical success, in which case the final success margin for the task is defined as +0.
When more than two actors are involved in a combined skill check, the checks are handled as a series of combined skill checks between two characters. Thus, if three characters were involved in a combined skill check, the success margin of the first two would be used as one actor's success margin in a combined skill check with the third.
A synergistic skill check occurs when a character uses multiple, related skills in conjunction to complete a task, or in any other situation that the interpretation or world rules define. The skill checks are handled in order. The success margin of each previous check is used to modify the Skill Value of the next check. Critical success and failures are treated as +10 and –10 success margins, respectively. For the first skill check in the series, the success margin of the previous check is defined as +0.
Any game that uses System X must allow three types of modifiers. The first type, the Skill Value modifier, is applied directly to the Skill Value of the character. The second type, the roll modifier, is applied directly to the twenty-sided die roll of the character. The third type, the success margin modifier, sets a minimum success margin that is required for any success on the action and must range from –5 to +5, or be a critical success or critical failure. Modifiers are defined for one character and for one use of the core resolution mechanic only, unless otherwise stated. The GM or game system may specify modifiers to any or all of these on any particular use of the core resolution mechanic.
Any game that is System X compliant or compatible must restrict the range of GM- specified Skill Value modifiers and roll modifiers to –4 to +4. The interpretation and world rules may still define modifiers outside this range. While individual GM modifiers may not exceed this range, a combination of smaller, interpretation or world rule specified modifiers, may produce a final modifier that exceeds this range.
Any roll after modifiers in a System X compliant or compatible game that exceeds 20 is always a critical success, and any roll that falls below 1 is always a critical failure.
A System X compliant game must implement a wound penalty, in which the maximum Skill Value usable by a character is equal to twice the remaining Wounds of the actor. Any Skill Values that exceed this value are reduced to it. The wound penalty is transient, changing as the character's remaining Wounds change. The wound penalty does not apply when the character has not taken any damage (i.e., when his remaining Wounds are equal to his maximum Wounds).
For tasks and events that are purely a function of probability, are unrelated to Skill Values, and have no logically possible success margin results, a game that uses System X may use the roll of the single twenty-sided die to determine success or failure without using the CRM. The interpretation or world rules fix a specific value under which the roll of the twenty-sided die must fall in order for the event to occur or the task to succeed.
Use of the flat probability task resolver is recommended for determining the occurrence of a probabilistic event only. It is strongly recommended that it be used sparingly, or not at all.