Bird Mutant Rift Brain

Based on game build 714014 | Last updated: 2026-02-27

Overview

This brain component implements the behavior tree for the Mutated Bird Rift entity (prefabs/bird_mutant_rift.lua). It manages high-level decisions such as fleeing from threats (environmental or living), consuming edible items, and mining Lunar Hail Buildup. It extends the base Brain class and constructs a priority-based behavior tree during initialization. The brain relies on multiple component states and properties, including health (fire damage), burnable (burning status), eater (diet preferences), and hauntable (panic state), to evaluate current conditions and select appropriate actions.

Dependencies & Tags

• Components used: burnable, eater, hauntable, health
• Tags checked (for filtering entities or items):
  • SHOULDFLYAWAY_CANT_TAGS: notarget, INLIMBO, lunar_aligned
  • SHOULDFLYAWAY_ONEOF_TAGS: player, monster, scarytoprey
  • FOOD_CANT_TAGS: FX, NOCLICK, DECOR, INLIMBO, outofreach
  • LUNARHAIL_BUILDUP_MUST_TAGS: LunarBuildup

Properties

Property	Type	Default Value	Description
inst	Entity	(injected by Class)	The entity instance this brain controls
bt	BT	nil (assigned in OnStart)	The behavior tree root node
threat	Entity?	nil (assigned on-demand)	Cached threat entity used by ShouldFlyAwayFromThreat

Main Functions

MutatedBirdBrain:OnStart()

• Description: Initializes and constructs the behavior tree root node for the brain. Sets up priority-based logic using PriorityNode and populates it with conditional and event-driven nodes (WhileNode, IfNode, EventNode, ActionNode, DoAction). The resulting tree is assigned to self.bt.
• Parameters: None.
• Returns: None.

IsSgBusy(inst)

• Description: Helper function that determines if the entity's current stategraph state has a tag indicating it is sleeping, busy, or in flight. Used to prevent conflicting behaviors (e.g., flying away while already in flight).
• Parameters:
  • inst: Entity — the entity instance to inspect.
• Returns: boolean — true if the stategraph state has any tag in {"sleeping", "busy", "flight"}, otherwise false.

ShouldFlyAway(inst)

• Description: Determines if the entity should flee due to unfavorable environmental conditions: (1) during nighttime in a new or quarter moon phase, or (2) when taking fire damage without being currently burning. It also ensures the entity is not already in a busy stategraph state.
• Parameters:
  • inst: Entity — the entity instance to evaluate.
• Returns: boolean — true if the entity should fly away, otherwise false.

ShouldFlyAwayFromThreat(inst)

• Description: Checks for the presence of a living threat within flight distance using FindEntity. Uses cached self.brain.threat when possible. Only evaluates if the entity is not in a busy state. Threats must match at least one tag in {"player", "monster", "scarytoprey"} and lack all tags in {"notarget", "INLIMBO", "lunar_aligned"}.
• Parameters:
  • inst: Entity — the entity instance to evaluate.
• Returns: boolean — true if a living threat is detected, otherwise false.

FlyAway(inst)

• Description: Triggers the "flyaway" event on the entity instance to initiate a flight behavior (e.g., transition to a flight stategraph).
• Parameters:
  • inst: Entity — the entity instance to act upon.
• Returns: None.

IsFood(item, inst)

• Description: Validates whether a given item is edible by the entity and is positioned on a passable tile.
• Parameters:
  • item: Entity — the candidate item to evaluate.
  • inst: Entity — the entity instance (used to check diet via eater component).
• Returns: boolean — true if the item is edible and passable, otherwise false.

FindFoodAction(inst)

• Description: Searches for the nearest valid food source within TUNING.RIFT_BIRD_FOOD_RANGE using FindEntity. Uses IsFood as the predicate and filters with FOOD_CANT_TAGS and edible item tags obtained from eater:GetEdibleTags(). If found, returns a BufferedAction for ACTIONS.EAT.
• Parameters:
  • inst: Entity — the entity instance to perform the search.
• Returns: BufferedAction? — a buffered eat action targeting the nearest edible item, or nil if no such item exists.

FindAndMineLunarHailBuildup(inst)

• Description: Searches for the nearest Lunar Hail Buildup within TUNING.RIFT_BIRD_FOOD_RANGE using FindEntity. Filters by LUNARHAIL_BUILDUP_MUST_TAGS and excludes items with FOOD_CANT_TAGS. If found, returns a BufferedAction for ACTIONS.REMOVELUNARBUILDUP.
• Parameters:
  • inst: Entity — the entity instance to perform the search.
• Returns: BufferedAction? — a buffered action to remove Lunar Hail Buildup, or nil if none exists.

Events & Listeners

• Listens to:
  • "threatnear" — triggers a fly_away_fn action via EventNode.
  • "gohome" — triggers a fly_away_fn action via EventNode.
• Pushes:
  • "flyaway" — fired by FlyAway when initiating departure.