Chapter 51 — Zone-Local Positioning

Chapter 51: Zone-Local Positioning

Design Constraint

No grid. No hexes. No distance tracking. Positioning is zone-based: entities occupy zones, zones have neighbors, and engagement statuses describe where you are relative to the fight. Four engagement states, two battlefield tags, and deterministic formula modifiers. If a pack needs richer spatial effects, use resources and abilities — not new engagement states.

Engagement State Reference

ENGAGED (engagement:engaged)

Role: In melee contact. You’re trading blows.

Property	Value
Applied by	combat hit (both attacker and target), entering a chokepoint zone
Cleared by	successful disengage, entity defeated, zone re-evaluation
Hit chance	+5 as target (easier to hit in melee)
Disengage	-15 penalty (harder to break free)
Reposition	-10 penalty (restricted movement)
AI response	Guard +5, Brace +10, Reposition targets backline enemies

Key behavior: ENGAGED is the default melee state. Any successful hit puts both sides into ENGAGED. Chokepoint zones force ENGAGED on entry regardless of combat contact. ENGAGED entities can intercept attacks on BACKLINE allies.

PROTECTED (engagement:protected)

Role: Shielded by an ally. A bodyguard is absorbing threat.

Property	Value
Applied by	ally with bodyguard tag in same zone
Cleared by	protector defeated, protector leaves zone, outflank
Guard reduction	+10% bonus (better defensive posture)
Intercept chance	+15% (bodyguard actively screening)
AI response	Brace +8 (protecting allies)

Key behavior: PROTECTED requires an active bodyguard-tagged ally in the same zone. When the protector is defeated or leaves, PROTECTED clears automatically. Outflank (successful targeted reposition) also removes PROTECTED.

BACKLINE (engagement:backline)

Role: Ranged or support position. You’re not in the thick of it.

Property	Value
Applied by	entity with ranged or caster tag, not ENGAGED, zone entry evaluation
Cleared by	combat hit (forced into melee), reposition into enemies
Hit chance	-10 as target (harder to reach)
Damage	-1 as attacker (ranged disadvantage in melee formulas)
Disengage	+15 bonus (easier to slip away)
Reposition	+10 bonus (freedom to maneuver)
AI response	Pressure targets BACKLINE exclusively, Reposition +15 vs backline targets

Key behavior: BACKLINE is for ranged/caster entities who haven’t been engaged in melee. It makes them harder to hit but limits their damage output. Any direct hit forces them out of BACKLINE into ENGAGED. BACKLINE entities are priority targets for the pressure intent. ENGAGED allies can intercept attacks targeting BACKLINE entities.

ISOLATED (engagement:isolated)

Role: Alone. No allies nearby.

Property	Value
Applied by	no same-type allies in zone
Cleared by	ally enters zone, zone re-evaluation
Damage	+2 taken (no one to share the load)
Disengage	-10 penalty (no covering fire)
AI response	Disengage +10

Key behavior: ISOLATED is automatically applied when an entity has no same-type allies in their zone. It clears immediately when an ally enters. Defeat of the last ally in a zone triggers ISOLATED on survivors.

Zone Tags

Chokepoint (chokepoint)

Role: Narrow passage. Favors defenders, punishes movement.

Effect	Value
Zone entry	Forces ENGAGED status, prevents BACKLINE
Disengage	-10 penalty (on top of ENGAGED’s -15)
Reposition	-15 penalty (no room to maneuver)
Brace stabilize	+15% chance (85% instead of 70%)

Key behavior: Chokepoints are defender-friendly zones. Braced defenders at chokepoints are extremely hard to destabilize (+15% stabilize vs off-balance). Movement through chokepoints is punished: disengage takes a -10 penalty and reposition takes -15. The combined effect of ENGAGED + chokepoint on disengage is -25.

Ambush Entry (ambush_entry)

Role: Concealed position. First contact favors occupants.

Effect	Value
Zone entry (with enemies)	Entering entity gets EXPOSED (duration 1 tick)
Zone entry (empty)	No effect
Event	combat.ambush.triggered emitted

Key behavior: When an entity enters an ambush_entry zone and enemies are already present, the entering entity receives the EXPOSED combat state. This grants the ambushers +20 hit chance and +2 damage on the first attack, after which EXPOSED clears. If the entity is already EXPOSED, no duplicate is applied.

Frontliner Screening

ENGAGED allies can intercept attacks targeting BACKLINE allies in the same zone. This is the “frontliner screens backliner” behavior.

Condition	Intercepts?
Player is target	Yes (always eligible for interception)
BACKLINE ally is target	Yes (ENGAGED allies can screen)
Non-backline, non-player target	No
Interceptor not ENGAGED	No (only frontliners screen)

The interception chance follows the same formula as player interception (default 30%, +15 if target is PROTECTED).

AI Zone Awareness

The AI evaluates exit zone quality when scoring disengage decisions:

Factor	Score
Non-chokepoint exit	+5
Exit zone has allies	+5
Exit zone has no enemies	+5

Maximum exit quality bonus: +15. The AI also selects the safest neighbor when actually disengaging (prefers non-chokepoint zones with allies).

Engagement vs Combat States

Engagement states and combat states are separate systems that coexist:

System	States	Duration	Applied by
Combat states	GUARDED, OFF_BALANCE, EXPOSED, FLEEING	1-2 ticks, auto-expire	Combat actions (guard, brace, attack, disengage, reposition)
Engagement states	ENGAGED, PROTECTED, BACKLINE, ISOLATED	Persistent until re-evaluated	Zone composition, entity tags, combat events

Both systems modify the same formulas (hit chance, damage, disengage chance) additively. An entity can be both ENGAGED and GUARDED, or both BACKLINE and EXPOSED. The effects stack.

Pack Author Rules

1. Do not add engagement states. Four is the cap. Use entity tags and zone tags for pack-specific positioning.

2. Use entity tags for roles. Tag entities ranged, caster, or bodyguard to opt into BACKLINE/PROTECTED mechanics.

3. Use zone tags for terrain. Mark zones as chokepoint or ambush_entry in your encounter definitions.

4. Resources can interact with positioning. Use TacticalHooks.movementModifier to let resources affect reposition/disengage success.

Module Registration

import { createEngagementCore, withEngagement, createEngagementNarration } from '@ai-rpg-engine/modules';

const engine = createEngine({
  modules: [
    statusCore,
    createEngagementCore({ playerId: 'player' }),
    createCombatCore(withEngagement(formulas)),
    createCombatTactics(),
    createEngagementNarration(), // optional, adds narrator text
  ],
});

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See Also

• Combat Overview — The six pillars and how they fit together
• Combat Tactics — Brace at chokepoints, reposition mechanics
• Combat States — GUARDED, OFF_BALANCE interact with engagement states
• Companion Interception — PROTECTED boosts interception chance
• Defeat Flow — Frontline collapse and ISOLATED state