Mind Scan

Mind Scan (34298391) is a Continuous Trap case study for information effects. It is not in the local cards.cdb at the time of this note, so this page is hand-written from the imported local script and the card details supplied from the Yugipedia card entry.

The script source is Scripts/c34298391.lua, imported from the local ygopro-scripts update ending at commit 06ccc5a99.

What The Card Needs

Mind Scan has two separate jobs:

Job	Script shape
Keep the opponent's hand revealed while you have a "Toon" card in your field or GY.	A field effect in the Spell & Trap Zone using EFFECT_PUBLIC and SetTargetRange(0,LOCATION_HAND).
Let you inspect the opponent's Set cards while that same condition is true.	A cloned field effect using EFFECT_REVEAL_ONFIELD, filtered to face-down cards on the opponent's field.
Once per turn, declare a card name that has not appeared earlier in the current Chain, then negate activated effects from cards with that original name until the End Phase while Mind Scan stays face-up.	A LOCATION_SZONE Quick Effect that stores the declared code, then registers an EVENT_CHAIN_SOLVING watcher.

The card's public-information effect is continuous-like. The declared-name negation is an activated Quick-like effect. Keeping those in separate effect objects makes the script easier to reason about.

Activation Shell

Like many Continuous Traps, the first effect simply activates the card:

local e1=Effect.CreateEffect(c)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetCode(EVENT_FREE_CHAIN)
c:RegisterEffect(e1)

The card's later effects are separate LOCATION_SZONE effects. Do not put the hand reveal, Set-card reveal, or declared-name negation inside the activation operation.

Revealing The Hand

The opponent's hand is handled by EFFECT_PUBLIC:

local e2=Effect.CreateEffect(c)
e2:SetType(EFFECT_TYPE_FIELD)
e2:SetCode(EFFECT_PUBLIC)
e2:SetRange(LOCATION_SZONE)
e2:SetCondition(s.picon)
e2:SetTargetRange(0,LOCATION_HAND)
c:RegisterEffect(e2)

The condition checks the controller's field and GY for a face-up or otherwise public "Toon" card:

function s.cfilter(c)
    return c:IsFaceupEx() and c:IsSetCard(0x62)
end
function s.picon(e)
    return Duel.IsExistingMatchingCard(s.cfilter,e:GetHandlerPlayer(),LOCATION_ONFIELD+LOCATION_GRAVE,0,1,nil)
end

Card.IsFaceupEx matters here because the GY is a public location. A plain IsFaceup check is usually for cards currently on the field.

Revealing Set Cards

Older scripts often had to force information updates manually with Duel.ConfirmCards. Mind Scan uses the local core-supported effect code EFFECT_REVEAL_ONFIELD instead:

local e3=e2:Clone()
e3:SetCode(EFFECT_REVEAL_ONFIELD)
e3:SetTarget(aux.TargetBoolFunction(Card.IsFacedown))
e3:SetTargetRange(0,LOCATION_ONFIELD)
c:RegisterEffect(e3)

This is a clean pattern for "you can look at Set cards" effects:

Piece	Why it is there
e2:Clone()	Reuses the same type, range, and condition as the hand-reveal effect.
EFFECT_REVEAL_ONFIELD	Marks affected on-field face-down cards as inspectable to the effect controller.
aux.TargetBoolFunction(Card.IsFacedown)	Limits the continuous effect to Set cards.
SetTargetRange(0,LOCATION_ONFIELD)	Applies only to the opponent's on-field cards.

This behavior is locally verified in ygopro-core: effect.h defines EFFECT_REVEAL_ONFIELD, card.cpp checks it for on-field cards, and effect.cpp treats it as a special code that can apply to face-down cards without the usual EFFECT_FLAG_SET_AVAILABLE requirement.

Declared-Name Quick Effect

The once-per-turn part is a separate Quick Effect:

local e4=Effect.CreateEffect(c)
e4:SetDescription(aux.Stringid(id,1))
e4:SetCategory(CATEGORY_DISABLE)
e4:SetType(EFFECT_TYPE_QUICK_O)
e4:SetCode(EVENT_FREE_CHAIN)
e4:SetRange(LOCATION_SZONE)
e4:SetHintTiming(0,TIMING_DRAW+TIMINGS_CHECK_MONSTER)
e4:SetCountLimit(1,id)
e4:SetCondition(s.accon)
e4:SetTarget(s.actg)
e4:SetOperation(s.acop)
c:RegisterEffect(e4)

The activation condition requires a Toon monster and a "Toon" Spell in the controller's field and/or GY:

function s.cfilter2(c)
    return c:IsFaceupEx() and c:IsType(TYPE_TOON)
end
function s.cfilter3(c)
    return c:IsFaceupEx() and c:IsSetCard(0x62) and c:IsType(TYPE_SPELL)
end
function s.accon(e)
    return Duel.IsExistingMatchingCard(s.cfilter2,e:GetHandlerPlayer(),LOCATION_MZONE+LOCATION_GRAVE,0,1,nil)
        and Duel.IsExistingMatchingCard(s.cfilter3,e:GetHandlerPlayer(),LOCATION_ONFIELD+LOCATION_GRAVE,0,1,nil)
end

Notice that the Toon monster check uses TYPE_TOON, while the "Toon" Spell check uses set code 0x62 plus TYPE_SPELL. Toon subtype and Toon archetype support are different questions.

Excluding Names Already Used In This Chain

The target function stores the announced card code as Chain target data. If this is Chain Link 1, any card can be announced:

local ac=Duel.AnnounceCard(tp)
Duel.SetTargetParam(ac)
Duel.SetOperationInfo(0,CATEGORY_ANNOUNCE,nil,0,tp,0)

If earlier Chain Links exist, the script collects their triggering cards, deduplicates their current codes, and passes an opcode filter to Duel.AnnounceCard:

local ch=Duel.GetCurrentChain()
local g=Group.CreateGroup()
for i=1,ch-1 do
    local te=Duel.GetChainInfo(i,CHAININFO_TRIGGERING_EFFECT)
    g:AddCard(te:GetHandler())
end

local codes={}
local ag=Group.CreateGroup()
for c in aux.Next(g) do
    local code=c:GetCode()
    if not ag:IsExists(Card.IsCode,1,nil,code) then
        ag:AddCard(c)
        table.insert(codes,code)
    end
end
table.sort(codes)

local afilter={codes[1],OPCODE_ISCODE}
for i=2,#codes do
    table.insert(afilter,codes[i])
    table.insert(afilter,OPCODE_ISCODE)
    table.insert(afilter,OPCODE_OR)
end
table.insert(afilter,OPCODE_NOT)
local ac=Duel.AnnounceCard(tp,table.unpack(afilter))
Duel.SetTargetParam(ac)

The important learner idea is not the opcode syntax itself. The important idea is that the forbidden names are gathered from the Chain that already exists, then Duel.AnnounceCard receives a filter that excludes those names.

Negating Matching Activated Effects

At resolution, Mind Scan checks that it is still face-up and related to the Chain, stores its current field ID, and registers a temporary watcher:

function s.acop(e,tp,eg,ep,ev,re,r,rp)
    local c=e:GetHandler()
    if c:IsRelateToChain() and c:IsFaceup() then
        local ac=Duel.GetChainInfo(0,CHAININFO_TARGET_PARAM)
        local fid=c:GetFieldID()
        c:RegisterFlagEffect(id,RESET_EVENT+RESETS_STANDARD+RESET_PHASE+PHASE_END,0,1,fid)
        local e1=Effect.CreateEffect(c)
        e1:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_CONTINUOUS)
        e1:SetCode(EVENT_CHAIN_SOLVING)
        e1:SetCondition(s.discon)
        e1:SetOperation(s.disop)
        e1:SetLabel(ac,fid)
        e1:SetLabelObject(c)
        e1:SetReset(RESET_PHASE+PHASE_END)
        Duel.RegisterEffect(e1,tp)
    end
end

The watcher negates matching activated effects as they resolve:

function s.discon(e,tp,eg,ep,ev,re,r,rp)
    local ac,fid=e:GetLabel()
    local ec=e:GetLabelObject()
    return ec:IsFaceupEx()
        and ec:GetFlagEffectLabel(id)==fid
        and re:GetHandler():IsOriginalCodeRule(ac)
end
function s.disop(e,tp,eg,ep,ev,re,r,rp)
    Duel.NegateEffect(ev)
end

IsOriginalCodeRule is the key name check here. The card text cares about the original card name, so a temporary name or code change should not dodge the declared-name restriction.

The field ID flag is the safety latch. If the original Mind Scan leaves the field and another copy appears, the old watcher should not keep working for the new card.

Common Mistakes

Mistake	Better pattern
Manually confirming Set cards over and over.	Use EFFECT_REVEAL_ONFIELD for continuous inspectability when the core supports it.
Using EFFECT_PUBLIC for Set cards on the field.	Use EFFECT_PUBLIC for the hand and EFFECT_REVEAL_ONFIELD for face-down on-field cards.
Checking only Card.IsFaceup in the GY.	Use Card.IsFaceupEx when the check spans field and public non-field locations.
Registering a lingering negate watcher without tying it to the source card.	Store the field ID and require the same face-up card to still be present.
Matching the declared name with IsCode.	Use IsOriginalCodeRule when the effect says original name.

API Links

• Effect.CreateEffect
• Effect.Clone
• Effect.SetType
• Effect.SetCode
• Effect.SetRange
• Effect.SetTargetRange
• Effect.SetTarget
• Effect.SetHintTiming
• Effect.SetCountLimit
• Effect.SetLabel
• Effect.SetLabelObject
• Duel.IsExistingMatchingCard
• Duel.GetCurrentChain
• Duel.GetChainInfo
• Duel.AnnounceCard
• Duel.SetTargetParam
• Duel.SetOperationInfo
• Duel.RegisterEffect
• Duel.NegateEffect
• Card.IsFaceupEx
• Card.IsFacedown
• Card.IsSetCard
• Card.IsType
• Card.IsRelateToChain
• Card.GetFieldID
• Card.RegisterFlagEffect
• Card.GetFlagEffectLabel
• Card.IsOriginalCodeRule
• Auxiliary.TargetBoolFunction
• Auxiliary.Next
• Constant reference

Related learning pages: Trap Card Patterns, Toon Monsters, Chain Timing And Activation Windows, Negation And Immunity, and Reset Flags And Effect Duration.