Can you respond to Void Assault with Crescent Strike, and does Void Assault resolve entirely before a combat showdown starts?

Ruling: You cannot respond to Void Assault with Crescent Strike because Crescent Strike is an [Action] spell, and only [Reaction] cards can be played during a closed state (when a chain exists). Void Assault resolves entirely—moving both the friendly unit and then the enemy unit—before any combat showdown begins.

Sequence:

• Opponent plays Void Assault, creating a chain and entering a closed state
• Only reactions can be played in response; actions like Crescent Strike cannot
• Once both players pass, Void Assault resolves completely: friendly unit moves, then enemy unit moves
• After the spell finishes resolving, if opposing units are at the same battlefield, a combat showdown begins

Nuances:

• You cannot interrupt a resolving spell to start a showdown; the entire spell effect must complete first
• Combat triggers like "When I Attack" or "When I Defend" are placed on a new chain after the spell fully resolves