Mermwatchtower

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

Overview

mermwatchtower is a world-interactive structure that spawns Merm guards (mermguard) when a Merm King exists anywhere in the world shard. It integrates with the childspawner component to manage guard deployment, responds to structural damage and burning, and dynamically adjusts its spawning rate based on kelp offering counts from nearby offering_pot structures. It also supports seasonal tuning via the iswinter world state and integrates with DST's deploy helper system for placement preview.

Usage example

-- Spawns the mermwatchtower entity
local inst = SpawnPrefab("mermwatchtower")
inst.Transform:SetPosition(x, y, z)

-- Manually trigger spawning if the Merm King is present
if TheWorld.components.mermkingmanager and TheWorld.components.mermkingmanager:HasKingAnywhere() then
    inst.components.childspawner:StartSpawning()
end

-- Manually update spawning rate from offering pots
inst:UpdateSpawningTime({ inst = some_player, count = 3 })

Dependencies & tags

Components used: burnable, childspawner, combat, deployhelper, inspectable, lootdropper, mermkingmanager, talker, updatelooper, worldsettingstimer, workable, fueled, propagator Tags: Adds structure. Checks burnt, placer, CLASSIFIED, NOCLICK.

Properties

Property	Type	Default Value	Description
kelpofferings	table	{}	Map of player GUID to offering count, used to compute dynamic regen multiplier.
UpdateSpawningTime	function	nil	Public method assigned to instance; updates regen period based on offering counts.
placerinst	Entity	nil	Reference to the entity placing this tower (used in placement helper).
helper	Entity	nil	Visual ring placed during placement preview (client-side only).

Main functions

UpdateSpawningTime(data)

• Description: Updates the child spawner's regen period based on the highest offering count in the local kelpofferings map. Called in response to ms_updateofferingpotstate events from the world.
• Parameters:
  data (table) — Expected fields: inst (offering pot entity), count (number of kelp offerings). Returns early if data.inst is invalid or too far (> WURT_OFFERING_POT_RANGE).
• Returns: Nothing.
• Error states: Returns early if inst.components.worldsettingstimer or inst.components.childspawner are missing.

OnEnableHelper(inst, enabled, recipename, placerinst)

• Description: Creates or destroys the placement helper ring entity (placerinst) when the deploy helper activates or deactivates.
• Parameters:
  enabled (boolean) — Whether helper mode is active.
  placerinst (Entity) — Reference to the entity doing the placement.
• Returns: Nothing.

StartSpawning(inst)

• Description: Begins spawning Merm guards if the Merm King is present, the structure is not burnt, and the childspawner component exists. Shows the flag animation and plays "flagup".
• Parameters:
  inst (Entity) — The mermwatchtower entity.
• Returns: Nothing.

StopSpawning(inst)

• Description: Stops spawning Merm guards. Plays "flagdown" animation to hide the flag. Does nothing if burnt.
• Parameters:
  inst (Entity) — The mermwatchtower entity.
• Returns: Nothing.

OnSpawned(inst, child)

• Description: Callback invoked after a Merm guard spawns. Plays a sound and stops spawning if it is daytime, at least one child is outside, and the spawned child has no target.
• Parameters:
  inst (Entity) — The watchtower instance.
  child (Entity) — The newly spawned mermguard.
• Returns: Nothing.

OnGoHome(inst, child)

• Description: Callback invoked when a Merm guard returns home. Plays a sound and resumes spawning if no guards remain outside.
• Parameters:
  inst (Entity) — The watchtower instance.
  child (Entity) — The returning mermguard.
• Returns: Nothing.

onhammered(inst, worker)

• Description: Executed when the watchtower is hammered. Extinguishes burning, removes childspawner, drops loot, spawns a collapse FX, and removes the entity.
• Parameters:
  inst (Entity) — The watchtower instance.
  worker (Entity) — The entity doing the hammering.
• Returns: Nothing.

onhit(inst, worker)

• Description: Executed when the watchtower is hammered but not destroyed. Releases all Merm guards, plays a "hit" animation sequence, and updates flag visibility.
• Parameters:
  inst (Entity) — The watchtower instance.
  worker (Entity) — The entity doing the hammering.
• Returns: Nothing.

onignite(inst)

• Description: On ignition, immediately releases all Merm guards.
• Parameters:
  inst (Entity) — The watchtower instance.
• Returns: Nothing.

onburntup(inst)

• Description: Sets the animation to "burnt" when the structure fully burns.
• Parameters:
  inst (Entity) — The watchtower instance.
• Returns: Nothing.

ToggleWinterTuning(inst, iswinter)

• Description: Adjusts the regen period multiplier during winter (x12 slower regen).
• Parameters:
  inst (Entity) — The watchtower instance.
  iswinter (boolean) — Whether it is winter.
• Returns: Nothing.

DescriptionFn(inst, viewer)

• Description: Returns the localized description string based on whether a Merm King is currently present.
• Parameters:
  inst (Entity) — The watchtower instance.
  viewer (Entity) — The player inspecting the tower.
• Returns: String — Either "MERMWATCHTOWER_REGULAR" or "MERMWATCHTOWER_NOKING" string key.

OnStartHelper(inst)

• Description: If placement animation is "place", stops helper mode early to prevent overlap.
• Parameters:
  inst (Entity) — The watchtower instance.
• Returns: Nothing.

onsave(inst, data)

• Description: Records burn state (burnt = true) in the save data.
• Parameters:
  inst (Entity) — The watchtower instance.
  data (table) — Save data table.
• Returns: Nothing.

onload(inst, data)

• Description: Restores burnt state on load by invoking onburnt.
• Parameters:
  inst (Entity) — The watchtower instance.
  data (table) — Loaded data, may contain data.burnt.
• Returns: Nothing.

OnPreLoad(inst, data)

• Description: Initializes childspawner values from save data using WorldSettings_ChildSpawner_PreLoad.
• Parameters:
  inst (Entity) — The watchtower instance.
  data (table) — Loaded save data.
• Returns: Nothing.

watchtower_on_animover(inst)

• Description: Ensures the flag is hidden after the "flagdown" animation completes and plays idle.
• Parameters:
  inst (Entity) — The watchtower instance.
• Returns: Nothing.

Events & listeners

• Listens to:

  • ms_updateofferingpotstate — Updates spawning time based on offering pot counts.
  • onbuilt — Plays build animation and sound, and updates flag visibility.
  • onignite — Releases guards when ignited.
  • burntup — Switches animation to burnt state.
  • onmermkingcreated_anywhere — Triggers spawning when a Merm King appears.
  • onmermkingdestroyed_anywhere — Triggers stopping spawning when a Merm King dies.
  • animover — Handles flag animation cleanup.

• Pushes: None.

Notes

• Deploy helper integration (deployhelper) is only added on non-dedicated clients.
• Spawning is conditional on TheWorld.components.mermkingmanager:HasKingAnywhere() returning true.
• During winter, regen time is multiplied by 12 (TUNING.MERMWATCHTOWER_REGEN_TIME * 12).
• Offering pots in range modify the ChildSpawner_RegenPeriod up to TUNING.WURT_MAX_OFFERING_REGEN_MULT times faster (up to MAX_COUNT offerings).
• The placement helper (placer) ring uses winona_battery_placement assets and a custom OnUpdatePlacerHelper to fade out when out of range.