Counter Traps

Counter Traps are Trap Card activations whose card type gives them Spell Speed 3. In script they still use EFFECT_TYPE_ACTIVATE; the local core reads TYPE_COUNTER from the handler and assigns the faster response speed.

The main beginner skill is choosing the correct negation family. A Counter Trap that negates a Summon is not resolving a Chain Link. A Counter Trap that responds to a Spell, Trap, or monster effect is answering EVENT_CHAINING.

Counter Trap Activation Shape

Solemn Judgment (c41420027.lua) shows both families on one card:

lua

local e1=Effect.CreateEffect(c)
e1:SetCategory(CATEGORY_DISABLE_SUMMON+CATEGORY_DESTROY)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetCode(EVENT_SUMMON)
e1:SetCondition(aux.NegateSummonCondition)
e1:SetCost(c41420027.cost1)
e1:SetTarget(c41420027.target1)
e1:SetOperation(c41420027.activate1)
c:RegisterEffect(e1)

local e4=Effect.CreateEffect(c)
e4:SetCategory(CATEGORY_NEGATE+CATEGORY_DESTROY)
e4:SetType(EFFECT_TYPE_ACTIVATE)
e4:SetCode(EVENT_CHAINING)
e4:SetCondition(c41420027.condition2)
e4:SetCost(c41420027.cost2)
e4:SetTarget(c41420027.target2)
e4:SetOperation(c41420027.activate2)
c:RegisterEffect(e4)

Both effects are EFFECT_TYPE_ACTIVATE. The event code decides which timing family each activation belongs to.

Summon Negation

Summon-negating Counter Traps listen to Summon events, usually cloning the same effect across Normal, Flip, and Special Summon windows:

lua

local e2=e1:Clone()
e2:SetCode(EVENT_FLIP_SUMMON)
c:RegisterEffect(e2)
local e3=e1:Clone()
e3:SetCode(EVENT_SPSUMMON)
c:RegisterEffect(e3)

The condition is commonly aux.NegateSummonCondition, sometimes with an extra card-specific filter. Chaos Trap Hole (c11593137.lua) adds an Attribute check:

lua

function c11593137.condition(e,tp,eg,ep,ev,re,r,rp)
    return aux.NegateSummonCondition() and eg:IsExists(c11593137.filter,1,nil)
end

The operation uses Duel.NegateSummon, then applies the card's follow-up:

lua

function c11593137.activate(e,tp,eg,ep,ev,re,r,rp)
    local g=eg:Filter(c11593137.filter,nil)
    Duel.NegateSummon(g)
    Duel.Remove(g,POS_FACEUP,REASON_EFFECT)
end

Do not use Duel.NegateActivation here. There is no Chain Link activation to negate in this timing family.

Activation Negation

Counter Traps that answer activated Spells, Traps, or monster effects usually listen to EVENT_CHAINING, check the triggering effect, and call Duel.NegateActivation(ev).

Dark Bribe (c77538567.lua) answers the opponent's Spell/Trap activation:

lua

function c77538567.condition(e,tp,eg,ep,ev,re,r,rp)
    return re:IsHasType(EFFECT_TYPE_ACTIVATE) and rp==1-tp and Duel.IsChainNegatable(ev)
end

Its operation negates that activation, destroys the activating card if it is still related, then draws for the opponent:

lua

function c77538567.activate(e,tp,eg,ep,ev,re,r,rp)
    if Duel.NegateActivation(ev) and re:GetHandler():IsRelateToEffect(re) then
        Duel.Destroy(eg,REASON_EFFECT)
    end
    Duel.Draw(1-tp,1,REASON_EFFECT)
end

That IsRelateToEffect(re) check matters because the handler being answered is the Chain Link's handler, not the Counter Trap itself.

Monster Effect Responses

Solemn Strike (c40605147.lua) and Divine Wrath (c49010598.lua) both answer monster effects with EVENT_CHAINING:

lua

function c40605147.condition(e,tp,eg,ep,ev,re,r,rp)
    return re:IsActiveType(TYPE_MONSTER) and Duel.IsChainNegatable(ev)
end

They still call Duel.NegateActivation(ev) because they are negating the activation of the monster effect Chain Link. That is different from applying a lingering disabled state to a monster.

Use Duel.NegateEffect(ev) when the script is negating a resolving effect without negating its activation. Local examples such as Infinite Impermanence and Mind Scan use Duel.NegateEffect from watcher effects after their own Trap activation has already resolved.

Spell Activation Filters

Some Counter Traps care about the kind of activation being answered. Spell Shield Type-8 (c38275183.lua) checks that the Chain Link is a Spell Card activation:

lua

return re:IsActiveType(TYPE_SPELL)
    and re:IsHasType(EFFECT_TYPE_ACTIVATE)
    and Duel.IsChainNegatable(ev)

That pair is useful:

re:IsActiveType(TYPE_SPELL) checks the active card/effect family.
re:IsHasType(EFFECT_TYPE_ACTIVATE) checks that the Chain Link is a card activation effect, not some other effect shape.

Announce The Right Operation

The target branch should announce what the Counter Trap is about to do.

lua

function c41420027.target2(e,tp,eg,ep,ev,re,r,rp,chk)
    if chk==0 then return true end
    Duel.SetOperationInfo(0,CATEGORY_NEGATE,eg,1,0,0)
    if re:GetHandler():IsDestructable() and re:GetHandler():IsRelateToEffect(re) then
        Duel.SetOperationInfo(0,CATEGORY_DESTROY,eg,1,0,0)
    end
end

For Summon negation, announce CATEGORY_DISABLE_SUMMON. For activation negation, announce CATEGORY_NEGATE. For follow-up destruction, banishing, drawing, or sending, announce those categories too.

Negation Families

Script family	Event	Common check	Operation
Summon negation	`EVENT_SUMMON`, `EVENT_FLIP_SUMMON`, `EVENT_SPSUMMON`	`aux.NegateSummonCondition()`	`Duel.NegateSummon(eg)`
Card/effect activation negation	`EVENT_CHAINING`	`Duel.IsChainNegatable(ev)` plus type/player checks	`Duel.NegateActivation(ev)`
Effect negation during resolution	usually watcher or resolving effect logic	Chain info or watched handler checks	`Duel.NegateEffect(ev)`
Lingering monster disable	normal Trap/Effect operation	targeted monster still legal	register `EFFECT_DISABLE` / `EFFECT_DISABLE_EFFECT`

Counter Traps most often use the first two rows. The last two rows are included because confusing them is a common source of broken scripts.

Common Pitfalls

Mistake	Better pattern
Writing a Counter Trap as `EFFECT_TYPE_QUICK_O`.	Use `EFFECT_TYPE_ACTIVATE`; `TYPE_COUNTER` supplies Spell Speed 3.
Calling `Duel.NegateActivation` in a Summon event.	Use `Duel.NegateSummon` with the Summoned group.
Calling `Duel.NegateSummon` while answering `EVENT_CHAINING`.	Use Chain APIs such as `Duel.NegateActivation(ev)`.
Forgetting `Duel.IsChainNegatable(ev)` on response effects.	Keep it with the card-specific Chain checks.
Destroying the Chain handler without checking relation.	Check `re:GetHandler():IsRelateToEffect(re)`.
Announcing only destruction.	Announce `CATEGORY_NEGATE` or `CATEGORY_DISABLE_SUMMON` as well.

Useful API Pages

Related lessons:

Counter Traps ​

Counter Trap Activation Shape ​

Summon Negation ​

Activation Negation ​

Monster Effect Responses ​

Spell Activation Filters ​

Announce The Right Operation ​

Negation Families ​

Common Pitfalls ​

Useful API Pages ​