This document defines the product direction and non-negotiable design rules for NPC intelligence in Island RPG. Implementation details may change, but new NPC features should preserve these principles.
NPCs are people living in the same world as the player. They are not quest dispensers, workforce units or followers waiting to be claimed. Every NPC has their own incomplete knowledge, needs, relationships, values and plans.
The player enters an existing social world. They may become a friend, rival, employee, follower, outsider or leader through play, but none of those roles is assumed merely because they are the player.
An NPC must not automatically know that a nearby actor is the player.
Before learning otherwise, the player is just an unknown person in the world. An NPC should not know the player's name, history, skills, inventory, intentions, reputation or importance unless that information was:
- directly observed;
- introduced in conversation;
- shared by another character;
- inferred from visible evidence; or
- remembered from an earlier encounter.
Systems must not leak player-only state into NPC decisions or dialogue. The runtime may use a player identifier to route events, but NPC reasoning must use an NPC-owned knowledge model. Unknown facts remain unknown, and beliefs may be incomplete, outdated or wrong.
Recognition should be earned and persistent. An NPC can forget uncertain details, confuse strangers, distrust a claim or recognize the player by prior behavior without knowing their name.
Each NPC chooses actions according to their own needs, commitments, relationships and circumstances. They can:
- accept, refuse, question or renegotiate a request;
- leave unsafe, unfair or unwanted situations;
- protect their own supplies and personal space;
- pursue work, rest, exploration and relationships without player input;
- disagree with the player and with other NPCs; and
- change priorities when new information or danger appears.
A direct player instruction is a social request, not an engine-level command. Following it depends on trust, authority, incentives, risk, capability and the NPC's current commitments.
NPC autonomy must not be implemented as random disobedience. Decisions should have understandable causes that can be communicated through behavior, conversation or inspectable intent.
Leadership is not reserved for the player. Any capable NPC may propose a plan, organize work, recruit help, manage shared resources, settle disputes or lead a group through danger.
Leadership should emerge from context such as:
- relevant skill or knowledge;
- earned trust and relationships;
- willingness to take responsibility;
- success or failure of previous plans;
- control of resources or a recognized social role; and
- support from other group members.
Different situations may produce different leaders. A skilled fisher may lead a food expedition while another NPC coordinates defence. Leadership can be contested, transferred, rejected or lost.
The player may support an NPC-led plan, negotiate an alternative, compete for influence or leave. NPC-led activity must remain able to progress without the player's attention.
Work roles such as Food, Wood, Crafting and Exploration describe a temporary coordination need. They do not make an NPC property of the player or permanently lock the NPC into a job.
Role assignment should eventually be expressed as a proposal or group decision. An NPC considers suitability, urgency, fairness, safety, personal goals and existing commitments before accepting. Roles must be revisited when conditions change.
Personal items remain personal. Shared storage, tools and food require an explicit group, household or settlement policy. Proximity to the player does not grant ownership or permission.
Relationships are directional. Mira may trust Rowan even when Rowan distrusts Mira. NPCs track experiences with individuals rather than using one universal attitude toward the player.
Important social state includes:
- identity knowledge and uncertainty;
- familiarity, trust, respect, fear and affection;
- promises, debts, grievances and witnessed behavior;
- group membership and recognized authority; and
- consent to follow, trade, share resources or cooperate.
Reputation is information transmitted through the social world, not a magical global score. Claims can spread unevenly and may be challenged by direct experience.
NPC decision-making should generally resolve concerns in this order:
- Immediate survival and self-defence.
- Dependants, promises and urgent social responsibilities.
- Current voluntary commitments and group plans.
- Personal needs, goals and relationships.
- New requests and opportunities.
- Low-priority idle activity.
This is guidance rather than a rigid behavior tree. Personality, urgency and context may change the result, but player requests do not receive an automatic top priority.
Autonomous behavior must be legible. The player should be able to understand, at an appropriate level, what an NPC is doing and why without seeing private implementation data.
Useful presentation includes:
- current activity and immediate intent;
- stated reasons for accepting or refusing a request;
- visible group roles and active plans;
- relationship changes tied to observed events; and
- uncertainty in dialogue when the NPC lacks information.
Do not expose exact hidden scores when natural language or behavior would communicate the same idea more convincingly.
New NPC systems should follow these constraints:
- NPC decisions consume observations and remembered beliefs, not unrestricted game state.
- Player identity is not a special fact in NPC memory; it is learned like any other actor identity.
- Shared action logic should work for players and NPCs where their physical capabilities are equivalent.
- Social permission and item ownership checks must apply consistently to all actors.
- Long-running NPC plans must persist and simulate without the player nearby.
- Deterministic gameplay services should be separated from rendering and AI narration.
- Important behavior needs scenario tests covering player and NPC initiators.
The NPC test matrix should grow to cover at least these cases:
- a stranger does not know or use the player's name;
- an introduction changes identity knowledge for only the participants;
- information can be learned second-hand with a recorded source;
- an NPC refuses a dangerous or unfair request for a clear reason;
- an NPC proposes and leads a group activity;
- another NPC accepts or rejects that leadership independently;
- an NPC-led plan continues while the player is absent;
- work roles change without treating the player as the permanent assigner;
- personal and shared storage obey the same permission rules for every actor; and
- hostility, trust and reputation remain directional rather than global.
- Add explicit actor identity knowledge: unknown, claimed, recognized and verified.
- Remove dialogue and decisions that read the player's name or status before an NPC has learned them.
- Represent requests as proposals with acceptance, refusal and reasons.
- Replace automatic work assignment with group proposals and voluntary role commitments.
- Add NPC-authored plans with a leader, participants, goal and lifecycle.
- Introduce group membership and explicit personal/shared resource policies.
- Expand observation tools and deterministic scenarios around NPC-led play.
Before approving an NPC feature, ask:
Would this behavior still make sense if the initiating character were an NPC and the player were absent?
If the answer is no, the feature should be redesigned or its player-specific exception should be explicit and justified.