I want a monster card's effect to gain the ATK of my opponent's highest monster while it's face-up on the field. For example, say my opponent summons Dark Magician. My monster's ATK becomes 2500. Then later in that same turn, my opponent summons Blue-Eyes White Dragon. My monster's ATK then becomes 3000.

However, I have no idea how to even begin coding this. I've looked at the scripts for Copycat and Widespread Ruin, but I don't quite understand them. Could I get a little advice?

local e1=Effect.CreateEffect(c)
e1:SetType(EFFECT_TYPE_SINGLE)
e1:SetCode(EFFECT_SET_ATTACK_FINAL)
e1:SetProperty(EFFECT_FLAG_SINGLE_RANGE)
e1:SetRange(LOCATION_MZONE)
e1:SetValue(cXXXXXXXX.adval)
c:RegisterEffect(e1)
function cXXXXXXXX.adval(e,c)
local g=Duel.GetMatchingGroup(cXXXXXXXX.filter,0,LOCATION_MZONE,LOCATION_MZONE,nil)
if g:GetCount()==0 then
return 0
else
local tg,val=g:GetMaxGroup(Card.GetAttack)
return val
end
end
function cXXXXXXXX.filter(c)
return c:IsFaceup() and c:GetCode()~=XXXXXXXX
end

Here you go, should work

Yep! That did it, and I understood what was done for the most part. Thanks, VB.