A.R.C. (Adaptive Resolution Core) System
Core Rules
The A.R.C. System uses percentile dice (d%) to resolve actions. Roll under your target number to succeed.
Two ten-sided dice (d10) to create percentile rolls
Character sheet
Imagination
Roll d%. If the result is equal to or under your target number, you succeed.
Rolling doubles creates critical results:
Doubles + Success = Critical Success (gain +1 SP)
Doubles + Failure = Critical Failure (lose -1 SP)
Regardless of your target number, a roll of 99 or 100 always fails. Because 99 shows doubles, it counts as a critical failure and costs 1 SP.
Four stats define your character:
Physical: Strength, endurance, health
Agility: Speed, reflexes, coordination
Intellect: Reasoning, memory, perception
Charisma: Presence, persuasion, leadership
Each stat starts at 50. Distribute 30 additional points among them.
Skills represent learned abilities. Each skill is based on a stat and starts at that stat's value.
Skills improve through use and training, not stat increases.
Skill Creation (Emergent Skills)
Skills are not selected from a master list.
Instead, skills are created through play.
When a player attempts an Active Action that represents a trained, deliberate activity, and no existing skill clearly applies, the GM and player name a new skill based on what the character is doing.
That new skill is now part of the character.
Examples:
Picking a lock → Lockpicking
Tracking footprints → Tracking
Researching ancient symbols → Ancient Lore
Repairing a generator → Mechanical Repair
Negotiating a truce → Negotiation
From that point forward, the character may use that skill whenever it applies.
The game does not attempt to catalog all possible skills.
Any learned activity can become a skill if it is used in play.
Some skills are common across many settings (such as Awareness, Stealth, or Persuasion), but players are never restricted to a predefined list.
If a player can describe a learned technique, it can be a skill.
Story Points (SP) measure how long a character remains in the story. They represent vitality, willpower, and narrative importance.
Player characters start with 5 SP
Lose 1 SP when hit in combat
Gain 1 SP on critical success
Lose 1 SP on critical failure
Recover SP through rest and healing
At 0 SP: character exits the story (death, retirement, etc.)
Active Actions require thought and deliberation. They use skills. If an Active Action does not match an existing skill, the action may create a new skill.
Roll d% under your skill value to succeed.
Reflexive Actions are instinctive responses. They use stats directly.
Examples:
Physical: Resist poison, endure pain
Agility: Dodge sudden danger, catch falling objects
Intellect: Resist mental influence, notice ambush
Charisma: Make first impression, command respect
Roll d% against Agility. Highest successful roll acts first. Failed rolls act in descending order after all successes.
Roll d% under your combat skill. Success means you hit. Damage reduces target's SP by 1.
Defender rolls d% under their defense skill to avoid the hit. Success negates damage.
Armor provides a penalty to attackers. Heavy armor might impose -20% to hit, light armor -10%. This reflects difficulty in landing damaging blows.
Equipment provides modifiers to relevant skills. A lockpick set might grant +10% to lockpicking. Quality tools matter.
Weapons don't increase damage - all hits deal 1 SP. Instead, weapons modify your chance to hit or provide tactical advantages.
Equipment lists are setting-specific.
Skill Improvement
Skills improve through use and practice. When you use a skill during a session, mark it on your character sheet. You can only mark each skill once per session, regardless of how many times you use it.
At the end of the session, you make improvement rolls for each marked skill. If this is the first time you have ever marked this particular skill for improvement, you automatically gain 1d10% added to that skill without rolling. This represents the rapid learning that comes from initial practice.
For all subsequent improvement attempts, roll d% for each marked skill. If you roll higher than your current skill value, you improve that skill by 1d10%. If you roll equal to or under your current skill value, you gain no improvement. This reflects how advanced practitioners learn less from routine use than novices do.
Example: Marcus has Climbing at 45%. During the session he climbed several obstacles and marked Climbing for improvement. At session end, he rolls 67 against his Climbing skill. Because 67 is higher than 45, he improves. He rolls 1d10 and gets 7, increasing his Climbing to 52%.
Stats rarely change. Growth comes through skills. The GM may allow stat increases for exceptional circumstances (superhuman transformation, divine blessing, etc.). Such changes should be rare and meaningful.
Assign SP based on narrative importance:
Nameless minions: 1 SP
Named supporting characters: 3-5 SP
Major antagonists: 7-10 SP
Campaign villains: 10+ SP
Modify target numbers based on task difficulty:
Easy: +20%
Moderate: No modifier
Difficult: -20%
Very Difficult: -40%
When characters oppose each other directly, both roll. Higher successful roll wins. If both fail, higher failed roll wins.
Adapting the System
Supernatural Abilities
Magic, psionics, superpowers, and other extraordinary abilities function as skills. A wizard's fire magic, a psychic's telepathy, or a mutant's energy projection all use the same mechanical framework as mundane skills. They can be learned, improved through use, and rolled when outcomes are uncertain.
Equipment and Tools
Appropriate equipment provides modifiers to skill checks. The quality and relevance of the tool determines the bonus. A set of lockpicks might grant +10% to Lockpicking. A high-quality telescope might provide +20% to Astronomy. Masterwork weapons could add +10% to combat skills. The GM assigns modifiers based on the situation and the equipment's quality.
This is a framework. Settings will provide:
Specific skill lists
Equipment and gear
World-specific rules
Character templates
Creatures and adversaries
The core mechanics remain constant. Settings add flavor and context.
License
Adaptive Resolution Core (A.R.C.) is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0).
You are free to copy, redistribute, remix, transform, and build upon this system for any purpose, including commercial use, provided appropriate credit is given.
Attribution must include:
“Based on Adaptive Resolution Core (A.R.C.) by Morris Penn.”
Jump straight into the action with eight ready-to-play characters spanning multiple genres. From urban witches to street samurai, post-apocalyptic survivors to pulp archaeologists; these pre-generated characters showcase the system's versatility. Pick one and start playing in minutes, or use them as templates for your own creations.