# Monster AI

* Monster AI scripts must be saved in the project folder/ServerScripts with a file name like Hello.lua to be read.

<table><thead><tr><th width="211">script</th><th>explanation</th></tr></thead><tbody><tr><td><strong>enemy</strong></td><td>Represents the ScriptUnit of a monster.</td></tr><tr><td><strong>ai</strong></td><td>Represents an AI behavior to be executed in ScriptEnemyUnitAI.</td></tr><tr><td><strong>event</strong></td><td>Check the logic to be executed.</td></tr><tr><td><strong>AI_INIT(-1)</strong></td><td>First run when registering monster AI</td></tr><tr><td><strong>AI_UPDATE(0)</strong></td><td>Keep running every 2 seconds</td></tr><tr><td><strong>AI_ATTACKED(1)</strong></td><td>Runs once per attack</td></tr><tr><td><strong>AI_DEAD(2)</strong></td><td>Runs once on death</td></tr><tr><td><strong>data</strong></td><td>It can only be used when attacking, and when (event == 1), you can check damage, skill ID, and whether it is critical (true, false) information.</td></tr></tbody></table>

Example) Server script - Setting monster AI

{% code overflow="wrap" lineNumbers="true" %}

```lua
 Server.SetMonsterAI(
        22, --Index of monsters to which AI will be applied
        function(enemy,ai,event,data)
        -- Runs when registering the first monster AI
        if(event == AI_INIT) then
                 ai.customData.test = 1;
        end
        if (event == AI_UPDATE) then
                --Returns the units that meet the condition among the units in the current field.
                --Example) Bring when there is an enemy with unit HP less than 100.
                --ai.SetTargetUnit(
                --        enemy.field.FindUnit(enemy.x, enemy.y, 200,
                --       function(u)
                --                return u.hp <= 100
                --        end
                --, 0,enemy))
                
                --Returns the unit that satisfies the smallest condition among the units in the current field.
                --Example) Bring the enemy with the lowest HP among the player units.
                --ai.SetTargetUnit(
                --        enemy.field.FindMinimumUnit(enemy.x, enemy.y, 200,
                --        function(u)
                --                return u.hp
                --        end
                --, 0,enemy))

                --Returns the unit that meets the largest condition among the units in the current field.
                --Example) Bring the enemy with the most HP among the player units.
                --ai.SetTargetUnit(
               --        enemy.field.FindMaximumUnit(enemy.x, enemy.y, 200,
                --        function(u)
                --               return u.hp
                --        end
                --, 0,enemy))
                
               --If no target is set, the closest player is targeted.
                if( ai.GetTargetUnit() == nil) then
                        ai.SetNearTarget(0,200)
                end
                
                --Set to null if there are no players on the map.
                if( enemy.field.playerCount <=0) then
                        ai.SetTargetUnit(nil)
                        
                --If the targeted player leaves the map, retarget.
                elseif(enemy.field.GetUnit(ai.GetTargetUnitID()) == nil) then
                        ai.SetNearTarget(0,200)
                end
                
                --If there is a target, attack in the direction of the target.
                ai.UseSkill(22);

                --Left attack
                ai.UseSkill(22,Point(-1,0))

                --Right attack
                ai.UseSkill(22,Point(1,0))

                --Attack from above
                ai.UseSkill(22,Point(0,1))

                --Downward attack
                ai.UseSkill(22,Point(0,-1))

                --Attack the location
                ai.UseSkillToPosition(24,Point(150,-150))
                
                --Exception handling when target is not found
                if(ai.GetTargetUnit() == nil) then
                        return
                end
                
                --Enable/disable tracking based on target's HP
                if(ai.GetTargetUnit().hp <=150) then
                        ai.SetFollowTarget(false)
                else
                        ai.SetFollowTarget(true)
               end
                
        end

       if (event == AI_ATTACKED) then
                enemy.Say('I was attacked. \nDamage: ' .. data.damage 
                .. '\nSkillID: '..data.skillDataID
                .. '\nWhether it is critical or not: '..(data.critical and 'true' or 'false'))
                
                --Exception handling when there is no unit attacking
                if(ai.GetAttackedUnit() == nil) then
                        return
               end
                 --Check the HP of the attacked enemy and change target if it is less than 100.
                if(ai.GetAttackedUnit().hp <= 100) then
                        ai.SetTargetUnit(ai.GetAttackedUnit()) 
                end

        end

        if (event == AI_DEAD) then
                Server.SendSay('dying')
                --Resurrect at a specific location after death
                enemy.RespawnAt(150,-150)
        end

end)
```

{% endcode %}

Example) Server script - Monster AI preemptive attack monster

{% code overflow="wrap" lineNumbers="true" %}

```
function firstAttack(enemy,ai,event,data)
    if (event == 0) then -- Event that runs every 2 seconds
    
        --Set to null if there are no players on the map.
        if enemy.field.playerCount <=0 then
            ai.SetTargetUnit(nil)
            
        -- If there is no target, or the existing target unit leaves the map, or the absolute value of the difference in x or y values ​​exceeds 300.
        -- Initialize target to nil and set target within 200 range
        elseif (ai.GetTargetUnit()==nil)
               or (enemy.field.GetUnit(ai.GetTargetUnitID())==nil)
               or (math.abs(enemy.x-enemy.field.GetUnit(ai.GetTargetUnitID()).x) >= 300) 
               or (math.abs(enemy.y-enemy.field.GetUnit(ai.GetTargetUnitID()).y) >= 300) then
            
            if ai.GetTargetUnit() ~= nil then
                enemy.say('The target is gone...')
            end
            
            ai.SetFollowTarget(false) --Disable tracking when target disappears
            ai.SetTargetUnit(nil)
            ai.SetNearTarget(0,200)

            -- When a target is found after searching the surroundings (if it is not nil), enable tracking (true) and output a message.
            if ai.GetTargetUnit() ~= nil then 
                ai.SetFollowTarget(true) 
                enemy.say('Target' detected! \nTracking begins!')
            end
        end
        
        --When a target exists, fire the skill 10 times toward the target.
        if ai.GetTargetUnit() ~= nil then
            ai.UseSkill(10)
        end
        
        --Exception handling when target is absent
        if ai.GetTargetUnit() == nil then
            return
        end
        
    end
    
    if (event == 1) then -- An event that runs whenever a monster is attacked.
        --Exception handling when there is no unit attacking
        if ai.GetAttackedUnit() == nil then
            return
        else
            --If the existing target unit and attacking unit are not the same, target or change the attacking unit and track it.
            if ai.GetTargetUnit() ~= ai.GetAttackedUnit() then 
                ai.SetTargetUnit(ai.GetAttackedUnit())
                ai.SetFollowTarget(true)
                enemy.say('Tracking a new attacker...')
            end
            
            -- When a monster is hit, there is a 10% chance that it will cast a special attack skill 5 times and then output a message to the entire server.
            if math.random(0,99) <= 9 then
                ai.UseSkill(5)
                Server.SendCenterLabel('<color=#FF0000>Crooked!!</color>\nStupid boss Badun cries!')
            end
        end
    end
        
end

Server.SetMonsterAI(1, firstAttack) -- Apply firstAttack to monster 1
```

{% endcode %}


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