Birdbrain

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

Overview

Birdbrain is a behavior tree-based AI brain component designed for bird-like entities. It determines when the entity should initiate flight (e.g., due to threats, environmental conditions, or external events) and executes the flyaway action. It uses a priority-based behavior tree (BT) with conditional nodes to evaluate real-time conditions such as panic state, time of day, fire damage, and proximity of hostile entities. The brain interacts with the hauntable, health, and burnable components to assess danger and adapt behavior accordingly.

Dependencies & Tags

• Components used:
  • hauntable: Reads panic property.
  • health: Reads takingfiredamage property.
  • burnable: Reads IsBurning() method.
• Tags checked:
  • lunar_aligned: Used to determine mutation state.
• Tags used in FindEntity (for threat detection):
  • SHOULDFLYAWAY_MUST_TAGS: "notarget", "INLIMBO" (must not be present on threat entities — used as canttags in FindEntity).
  • SHOULDFLYAWAY_CANT_TAGS: "player", "monster", "scarytoprey" (at least one must be present on a threat entity — used as oneoftags in FindEntity).

Properties

Property	Type	Default Value	Description
inst.flyawaydistance	number (expected)	Not defined in Birdbrain	Used by FindEntity to limit detection radius for threats. Must be defined on the instance elsewhere.

Main Functions

BirdBrain:OnStart()

• Description: Initializes the behavior tree for the bird entity. Constructs a priority-based BT root node with four conditions that trigger the flyaway action: panic (from hauntable), ShouldFlyAway conditions, "threatnear" event, and "gohome" event. The behavior tree runs at a .25 second interval.
• Parameters: None.
• Returns: nil.

ShouldFlyAway(inst) (local function)

• Description: Evaluates whether the entity should fly away based on multiple criteria:
  • Entity is not in sleeping, busy, or flight states.
  • One or more of:
    • It is nighttime (TheWorld.state.isnight).
    • Lunar hail is active (TheWorld.state.islunarhailing).
    • Taking fire damage and not currently burning (to avoid double-counting fire-related threats).
    • A nearby entity exists that satisfies the threat criteria (via FindEntity).
• Parameters:
  • inst (Entity): The bird entity instance.
• Returns: boolean — true if the entity should fly away, false otherwise.

FlyAway(inst) (local function)

• Description: Triggers the flyaway event on the instance to signal the start of flight behavior.
• Parameters:
  • inst (Entity): The bird entity instance.
• Returns: nil.

Events & Listeners

• Listens to: "threatnear" (via EventNode in behavior tree), "gohome" (via EventNode in behavior tree).
• Pushes: "flyaway" (via inst:PushEvent("flyaway") when triggered by behavior nodes).