When Anivia moves to an occupied battlefield and her attack trigger kills the defending unit during the initial chain, do players get action windows during the showdown steps?

Ruling: The showdown still proceeds through all its normal steps with focus windows for both players, even though the defender was killed during the initial chain. Players cannot play action cards in response to Anivia's When I Attack trigger because it's on a chain (closed state).

Sequence:

• Anivia moves to occupied battlefield, starting a showdown
• Initial chain: Anivia's attack trigger activates and resolves, killing the defending unit
• Showdown proceeds through all normal steps with attacker/defender focus windows
• Players gain focus and opportunities to play cards during these windows
• After all showdown steps complete, a point is scored

Nuances:

• No action cards can be played during the initial chain while Anivia's trigger is resolving (closed state)
• The attacker/defender focus pattern continues even though the defender is dead
• Points are only scored after all showdown steps unless a card specifically states otherwise (like Yasuo's 3rd move)