Turret

Introduction

A Turret is a programmable structure in space that projects offensive or defensive power over a fixed location. It is anchored on a base (grid), draws power from the network node, and automatically engages targets within its proximity. The game continuously evaluates nearby entities and asks which target to shoot and in what order—either using built-in default logic or your custom extension.

Default Behavior

By default (no extension configured), the game uses the built-in logic in the world turret contract to decide which targets to shoot. Default rules:

• Exclude — same tribe as owner and not an aggressor; or target stopped attacking

• Prioritize — started attacking adds a large weight increment; entered proximity adds a smaller weight if different tribe or aggressor

• The game shoots the target with the highest priority weight; ties use list order.

Custom Behavior (Extension)

When the owner configures an extension, the game uses that extension’s logic instead of the default to decide which targets to shoot and in what order. The extension receives the same target information the game uses and returns a custom priority list.

1. The owner deploys custom targeting logic (a Move contract) and registers it as the turret’s extension.

2. Whenever the game evaluates targets, it calls that logic and uses the returned list to choose what to shoot.

Behaviours

The game calls your extension whenever target behaviour changes (e.g. a ship enters range, starts or stops attacking). It sends exactly one behaviour change per candidate; if both ENTERED and STARTED_ATTACK apply, the game sends STARTED_ATTACK (the higher-priority). Your extension returns which targets to shoot and at what priority weight; the game shoots the highest-weight target, and uses list order to break ties.

Behaviour reasons:

• ENTERED — target entered the turret’s proximity

• STARTED_ATTACK — target started attacking the base (or someone on grid)

• STOPPED_ATTACK — target stopped attacking

Target candidate and return structs (from the world turret module):

public struct TargetCandidate has copy, drop, store {
    item_id: u64,
    type_id: u64,
    group_id: u64,
    character_id: u32,
    character_tribe: u32,
    hp_ratio: u64,
    shield_ratio: u64,
    armor_ratio: u64,
    is_aggressor: bool,
    priority_weight: u64,
    behaviour_change: BehaviourChangeReason,
}

public struct ReturnTargetPriorityList has copy, drop, store {
    target_item_id: u64,
    priority_weight: u64,
}

TargetCandidate field meanings:

Field	Meaning
item_id	Unique id for the target (ship_id / npc_id).
type_id	Target type (ship or NPC).
group_id	Ship group; helps prioritize by ship class. 0 for NPCs.
character_id	Pilot character id; 0 for NPCs.
character_tribe	Character tribe; 0 for NPCs.
hp_ratio, shield_ratio, armor_ratio	Remaining structure/shield/armor as percentage (0–100).
is_aggressor	True if this target is attacking anyone on grid (structure or player).
priority_weight	Default weight from game; your extension can override via the return list.
behaviour_change	The single reason sent for this candidate (e.g. STARTED_ATTACK over ENTERED when both apply).

Return list: the game shoots the target with the highest priority_weight in your returned list; if equal, it uses the order in the list.

Ship groups and turret specialization

Turret types in the game are specialized against certain ship groups. You can use group_id to prefer targets your turret is good against:

Ship class	group_id
Shuttle	31
Corvette	237
Frigate	25
Destroyer	420
Cruiser	26
Combat Battlecruiser	419

Turret type	type_id	Specialized against (group_ids)
Autocannon	92402	Shuttle (31), Corvette (237)
Plasma	92403	Frigate (25), Destroyer (420)
Howitzer	92484	Cruiser (26), Combat Battlecruiser (419)

Next Steps

Build and test a custom turret extension: Build Guide

Reference:

• world-contracts — EVE Frontier Sui Move contracts

• turret.move — core turret module

• extension_examples/turret.move — example custom turret extension

• contracts/world — world contract package