[Chalkarts]

I’m still trying to master the rules of alchemy.
If I used for a preparation a playing card and infused it with stunball, is the spell centered on the card or can it be launched if I’m holding the card?

If I put the card on someone’s desk and call the command word to set off the stunball I assumed it went off centered on the card like a grenade.
But if I’m holding the card can I cast it at range as normal?

[Stainless Steel Devil Rat]

I’m still trying to master the rules of alchemy.
If I used for a preparation a playing card and infused it with stunball, is the spell centered on the card or can it be launched if I’m holding the card?

If I put the card on someone’s desk and call the command word to set off the stunball I assumed it went off centered on the card like a grenade.
But if I’m holding the card can I cast it at range as normal?

Depends on how you enchant the trigger.  Off the cuff, I believe I remember that the spell goes off on the person activating the card. If you want to put a hostile spell into a playing card, you have to get/trick the target into touching it.

[Kiirnodel]

Area spells are always centered on the object that was prepared.

[Mirikon]

Area spells are always centered on the object that was prepared.

Kiirnodel is correct. An AoE spell would go off around the object, affecting everything within range. Touch range spells affect the one touching the item. Line of Sight spells can be targeted if it is a Command trigger, otherwise it looks for the closest viable target.