attack Chandra Nalaar trample damage go to player magic

[vacation]

if I attack a Chandra Nalaar with a creature with trample such as a Molder Beast and it goes unblocked, and my creature has more then power to reduce the planeswalker to 0 loyalty points, does remaining damage go to player?

[Arix]

No, it all goes to the planeswalker.

[Soddda]

why does it say "assign the rest of its damage to defending player or planeswalker" implying you can choose to assign remaining damage to planeswalker?

[Arix]

Because...you can?

You attack either the player or the planeswalker. If it's blocked and kills its blockers, the remaining damage can go over to whatever you attacked - planeswalker or player. You can't spill the damage over form the planeswalker to the player though, since if you're attacking the planeswalker then you're not attacking the player and therefore can't deal damage to them.