Trap Card Patterns

Trap Cards share the same card-activation effect shape as Spells, but their timing rules are different. Normal Traps and Continuous Traps activate at Spell Speed 2. Counter Traps activate at Spell Speed 3.

In script terms, all of those card activations still use EFFECT_TYPE_ACTIVATE; the Trap's card type decides the activation speed.

Focused follow-up lessons:

The Shared Trap Activation Shape

lua

local e1=Effect.CreateEffect(c)
e1:SetCategory(CATEGORY_DISABLE)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
e1:SetCode(EVENT_FREE_CHAIN)
e1:SetTarget(s.target)
e1:SetOperation(s.activate)
c:RegisterEffect(e1)

Local core behavior treats TYPE_TRAP activations as Spell Speed 2 and TYPE_COUNTER activations as Spell Speed 3. It also checks whether a Trap is being activated from the hand or during the turn it was Set.

Those exceptions are not written into the activation effect itself. They are usually granted as separate single effects:

Exception	Common effect code
Activate a Trap from the hand	`EFFECT_TRAP_ACT_IN_HAND`
Activate a Trap during the turn it was Set	`EFFECT_TRAP_ACT_IN_SET_TURN`

Normal Traps

A Normal Trap often looks like a Quick-Play Spell from the callback point of view: target branch, operation branch, relation checks, and optional hint timing.

Infinite Impermanence (c10045474.lua) uses a normal activation effect and a separate hand-activation permission:

lua

local e1=Effect.CreateEffect(c)
e1:SetCategory(CATEGORY_DISABLE)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
e1:SetCode(EVENT_FREE_CHAIN)
e1:SetHintTiming(0,TIMINGS_CHECK_MONSTER)
e1:SetTarget(s.target)
e1:SetOperation(s.activate)
c:RegisterEffect(e1)

local e2=Effect.CreateEffect(c)
e2:SetType(EFFECT_TYPE_SINGLE)
e2:SetCode(EFFECT_TRAP_ACT_IN_HAND)
e2:SetCondition(s.handcon)
c:RegisterEffect(e2)

The activation target still follows ordinary targeting rules:

lua

function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
    if chkc then
        return chkc:IsLocation(LOCATION_MZONE)
            and chkc:IsControler(1-tp)
            and aux.NegateMonsterFilter(chkc)
    end
    if chk==0 then
        return Duel.IsExistingTarget(aux.NegateMonsterFilter,tp,0,LOCATION_MZONE,1,nil)
    end
    Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_DISABLE)
    Duel.SelectTarget(tp,aux.NegateMonsterFilter,tp,0,LOCATION_MZONE,1,1,nil)
end

Trap Trick (c80101899.lua) shows the Set-from-Deck pattern. It checks IsSSetable, Sets the matching Trap, then grants that Set card EFFECT_TRAP_ACT_IN_SET_TURN.

lua

function s.setfilter(c,code)
    return c:IsCode(code) and c:IsSSetable()
end

if tc2 and Duel.SSet(tp,tc2)~=0 then
    local e1=Effect.CreateEffect(c)
    e1:SetType(EFFECT_TYPE_SINGLE)
    e1:SetCode(EFFECT_TRAP_ACT_IN_SET_TURN)
    e1:SetProperty(EFFECT_FLAG_SET_AVAILABLE)
    e1:SetReset(RESET_EVENT+RESETS_STANDARD)
    tc2:RegisterEffect(e1)
end

This is a good example of separating the movement action from the later activation exception. Duel.SSet places the card; the single effect changes when the newly Set Trap may be activated.

Use Normal And Continuous Traps for the focused one-shot activation, hand exception, and set-turn exception guide.

Continuous Traps

A Continuous Trap usually has a small activation effect, then separate effects that work while the card remains face-up in the Spell & Trap Zone.

lua

local e0=Effect.CreateEffect(c)
e0:SetType(EFFECT_TYPE_ACTIVATE)
e0:SetCode(EVENT_FREE_CHAIN)
c:RegisterEffect(e0)

local e1=Effect.CreateEffect(c)
e1:SetDescription(aux.Stringid(id,0))
e1:SetType(EFFECT_TYPE_QUICK_O)
e1:SetCode(EVENT_FREE_CHAIN)
e1:SetRange(LOCATION_SZONE)
e1:SetCountLimit(1,EFFECT_COUNT_CODE_SINGLE)
e1:SetHintTiming(0,TIMING_END_PHASE)
e1:SetTarget(s.target)
e1:SetOperation(s.operation)
c:RegisterEffect(e1)

Cyberdark Invasion (c1157683.lua) uses this structure: one activation effect places the Continuous Trap face-up, then two Quick Effects are registered with SetRange(LOCATION_SZONE).

Mind Scan (c34298391.lua) is a newer Continuous Trap example with a different shape: it has a small activation effect, a continuous hand-reveal effect, a continuous Set-card inspection effect using EFFECT_REVEAL_ONFIELD, and a separate once-per-turn Quick Effect. See the Mind Scan case study for the full pattern.

For Continuous Traps, EFFECT_TYPE_ACTIVATE is not the same thing as the card's later face-up effects. The activation effect gets the card onto the field. The later effects describe what the face-up Trap can do.

The focused Normal And Continuous Traps page also covers SetRange, SetTargetRange, reset behavior, and leave-field cleanup.

Counter Traps

Counter Traps still register EFFECT_TYPE_ACTIVATE, but TYPE_COUNTER makes their activation Spell Speed 3 in the local core.

Chaos Trap Hole (c11593137.lua) is a compact local summon-negation pattern:

lua

local e1=Effect.CreateEffect(c)
e1:SetCategory(CATEGORY_DISABLE_SUMMON+CATEGORY_REMOVE)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetCode(EVENT_SUMMON)
e1:SetCondition(s.condition)
e1:SetCost(s.cost)
e1:SetTarget(s.target)
e1:SetOperation(s.activate)
c:RegisterEffect(e1)

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

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

The operation negates the Summon, then banishes the Summoned monster:

lua

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

Counter Traps that negate card or effect activations usually listen to EVENT_CHAINING, check the Chain Link with Duel.IsChainNegatable(ev), then call Duel.NegateActivation(ev) during resolution.

Do not use Duel.NegateSummon for Chain Link negation. Summon negation and activation negation are different timing families.

Use Counter Traps for the focused summon-negation, activation-negation, and effect-negation distinction.

Trap Cards Leaving Or Staying

Normal Traps and other non-continuous Spell/Trap Cards activated on the field are normally confirmed to go to the GY after their Chain handling. The generated API page for Card.CancelToGrave documents the local helper used by scripts that need to keep such a card on the field or make a replacement pattern work.

Most Trap scripts do not call CancelToGrave. Use it only when a matching local script pattern needs to override the normal post-activation destination.

Common Pitfalls

Mistake	Safer pattern
Writing a Counter Trap as `EFFECT_TYPE_QUICK_O`.	Use `EFFECT_TYPE_ACTIVATE`; `TYPE_COUNTER` gives the card activation Spell Speed 3.
Putting Continuous Trap effects inside the activation effect.	Register a small activation effect, then separate `LOCATION_SZONE` effects.
Setting a Trap from the Deck and assuming it can activate immediately.	Grant `EFFECT_TRAP_ACT_IN_SET_TURN` only when the card text allows it.
Letting a Trap activate from the hand by target logic alone.	Add an `EFFECT_TRAP_ACT_IN_HAND` single effect with its own condition.
Using `Duel.NegateSummon` to answer an activated effect.	Use `Duel.NegateActivation` for Chain Link activation negation.

Useful API pages:

Trap Card Patterns ​

The Shared Trap Activation Shape ​

Normal Traps ​

Continuous Traps ​

Counter Traps ​

Trap Cards Leaving Or Staying ​