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Birds Mutant

Based on game build 714014 | Last updated: 2026-03-04

Overview​

birds_mutant.lua defines two prefabs—bird_mutant (runner) and bird_mutant_spitter (spitter)—which are hostile lunar creatures summoned during the Moonstorm event. It sets up shared and variant-specific behavior using core components including combat, entitytracker, eater, locomotor, health, sleeper, sanityaura, and lootdropper. The spitter variant adds a custom LaunchProjectile method to fire bile projectiles. Prefab creation is split into commonPreMain (core entity setup) and commonPostMain (component registration), both called by runnerfn and spitterfn.

Usage example​

-- Creating a runner mutant bird
local runner = Prefab("bird_mutant", "prefabs/birds_mutant")
local entity = runner()

-- Creating a spitter mutant bird with projectile support
local spitter = Prefab("bird_mutant_spitter", "prefabs/birds_mutant")
local spitter_entity = spitter()

-- Launch a projectile from spitter (master only)
if TheWorld.ismastersim then
    spitter_entity.LaunchProjectile(spitter_entity, target_pos)
end

Dependencies & tags​

Components used: combat, complexprojectile, eater, entitytracker, health, inventoryitem, locomotor, lootdropper, sanityaura, sleeper, inspectable, timer, knownlocations, occupier

Tags added/checked:
bird_mutant, NOBLOCK, soulless, hostile, monster, scarytoprey, canbetrapped, bird, lunar_aligned, bird_mutant_spitter (spitter only)
Also adds/_removes inspectable and scarytoprey dynamically on combat events.

Properties​

No public properties are defined in the constructor. Component behavior is configured via calls to component methods.

Main functions​

commonPreMain(inst)​

  • Description: Initializes core entity infrastructure (transform, animstate, physics, sound emitter, dynamic shadow, tags, animation). Called before component setup in both prefabs.
  • Parameters: inst (Entity) - the entity being constructed.
  • Returns: inst (Entity).
  • Error states: None. Sets up foundational entity state.

commonPostMain(inst)​

  • Description: Adds and configures all gameplay components (combat, eater, sleeper, sanityaura, locomotor, health, entitytracker, inventoryitem, lootdropper, knownlocations), sets the stategraph, assigns brain, and enables hauntable/feedable behavior.
  • Parameters: inst (Entity) - the entity being constructed.
  • Returns: inst (Entity).
  • Error states: None. Requires commonPreMain to have been called first.

LaunchProjectile(inst, targetpos)​

  • Description: Spawns a bilesplat projectile and launches it toward targetpos using complexprojectile. Speed is scaled linearly with distance. Used exclusively by bird_mutant_spitter.
  • Parameters:
    inst (Entity) - the spitter instance launching the projectile.
    targetpos (Vector3) - world position of the projectile target.
  • Returns: Nothing.
  • Error states: Projectile is placed at launcher's position and accelerated based on TUNING.FIRE_DETECTOR_RANGE.

Retarget(inst)​

  • Description: Finds a new combat target within aggro range if near the swarm target or if swarm target is absent. Uses FindEntity with tags and IsValidTarget.
  • Parameters: inst (Entity) - the mutant bird instance.
  • Returns: Entity or nil.
  • Error states: Returns nil if no valid target found or swarm target is too far.

IsValidTarget(guy, inst)​

  • Description: Determines if a given entity guy is a valid combat target for inst. Accepts players or player-led followers if combat:CanTarget passes.
  • Parameters:
    guy (Entity) - candidate target.
    inst (Entity) - the mutant bird instance.
  • Returns: boolean.
  • Error states: Returns false if guy is nil, lacks combat capability, or is not a player/owned follower.

KeepTargetFn(inst, target)​

  • Description: Decides whether to retain the current combat target based on proximity and validity. Used as the keepfn for combat retargeting.
  • Parameters:
    inst (Entity) - the mutant bird instance.
    target (Entity) - current target.
  • Returns: boolean.
  • Error states: Returns false if target is out of return distance or invalid.

Events & listeners​

  • Listens to:
    newcombattarget → OnNewCombatTarget (adds inspectable and scarytoprey tags)
    droppedtarget → OnNoCombatTarget (removes inspectable, restarts combat cooldown)
    losttarget → OnNoCombatTarget
    ontrapped → OnTrapped (restores trapped build if applicable)
  • Pushes: None.