Moon Device

Based on game build 714014 | Last updated: 2026-03-06

Overview

The moon_device prefab represents a multi-stage structure that initiates and manages the Moon Altar boss event in DST. It is constructed in three stages (moon_device_construction1 → moon_device_construction2 → moon_device), and upon reaching the final stage (level == 3), it automatically begins a countdown before triggering the boss spawn and associated effects. It relies on placement directly atop an existing moon_altar_link, and integrates tightly with construction, placement, and environmental destruction systems.

Usage example

-- Typical usage inside the game's startup sequence
-- This prefab is auto-registered via MakeDeviceStage and returned by the script.
-- Modders typically interact with it indirectly through construction and events.

-- Example: Accessing properties after the device is built
if TheWorld.map:GetTag("CELESTIAL_ORB_FOUND") then
    print("Moon Device reached stage 2 or 3; Celestial Orb recipes unlocked.")
end

Dependencies & tags

Components used: constructionsite, inspectable, placer, health, combat, container, mine, inventoryitem, workable
Tags added: moon_device, structure, nomagic, antlion_sinkhole_blocker, constructionsite (only during construction stages)
Tags checked: moon_altar_link, can_build_moon_device, smashable, irreplaceable, FX, ghost, INLIMBO, NOCLICK, playerghost, _combat, _inventoryitem, CHOP_workable, DIG_workable, HAMMER_workable, MINE_workable, moonglass

Properties

Property	Type	Default Value	Description
level	number	3 (for full device), 1 or 2 (for construction stages)	Current construction/activation stage; used to determine behavior and animations.
_pillars	table	nil	Array of 4 pillar entities spawned at level >= 2.
_top	entity	nil	Top component entity spawned at level == 3.
_link	entity	nil	moon_altar_link_contained entity used for visual tether.
_has_replaced_moon_altar_link	boolean	false	Tracks whether the original moon_altar_link has been replaced and removed.
_construction_product	string	nil	Name of the prefab this stage builds into (e.g., "moon_device_construction2").

Main functions

No user-facing methods exist for external callers—this is a prefab definition script that constructs entities via factory functions. All logic is internal to prefab construction and event-driven callbacks. However, the following internal helpers play critical roles:

OnConstructed(inst, doer)

• Description: Checks if construction materials meet the required amounts per CONSTRUCTION_PLANS. If so, replaces this construction-site entity with the next upgrade prefab (_construction_product) and plays sound/animation for level transitions.
• Parameters: inst (entity) — the construction site entity; doer (entity) — not used.
• Returns: Nothing.
• Error states: Silently skips replacement if material counts are insufficient.

ClearArea(inst)

• Description: During device destruction (stage 1 break), this clears a 15-radius area by applying various effects (altar-specific FX, kill, destroy, damage, launch) to entities in range, depending on their components and tags.
• Parameters: inst (entity) — the moon device being destroyed.
• Returns: Nothing.

breaksequence(inst)

• Description: Starts the countdown sequence leading to boss spawn. Spawns a falling FX, waits ~9 frames, then triggers break_device, which in turn spawns break FX, scorch marks, and finally spawns the alterguardian_phase1 boss.
• Parameters: inst (entity) — the moon device entity.
• Returns: Nothing.

placer_onupdatetransform(inst)

• Description: Snap-to-grid logic for the construction placer: finds nearest moon_altar_link, snaps position, and sets accept_placement based on the linker's can_build_moon_device tag.
• Parameters: inst (entity) — the placer entity.
• Returns: Nothing.

placer_override_testfn(inst)

• Description: Overrides placement test to enforce placement only when a valid moon_altar_link is nearby, ignoring standard block checks (water, etc.) to avoid blocking progression.
• Parameters: inst (entity) — the placer entity.
• Returns: can_build, mouse_blocked — booleans (always inst.accept_placement, false respectively).

Events & listeners

• Listens to:
  • onbuilt — triggers base_onbuilt, playing construction sound and animation.
  • onremove — clears the global existing_moon_device reference.
• Pushes: None directly (events are emitted by other components it uses, e.g., construction system fires onbuilt).

Notes

• Only one moon_device instance is permitted; if a second is created, it removes itself.
• At stage 2 or 3, the world tag CELESTIAL_ORB_FOUND is enabled, unlocking related crafting recipes.
• The device is only valid when built directly on top of a moon_altar_link; otherwise, it removes itself during validate_spawn.
• The countdown to boss spawn (BREAK_DELAY = 9.5 seconds) starts immediately upon reaching level 3, unless POPULATING is true (e.g., worldgen load), in which case the meteor spawner is deferred.