We have had a couple of games and only yoday has this query come up.
We have been playing in accordance with the physical damage rule.
But does this extend to the final battle?
We fought against YIG and could not see where it mentioned he was immune to physical attacks on his card (or in the rule book in regards all GOO's).
If he is vunerable then we managed a win if not we got devoured in turn 3.