Can you play an action spell (like Primal Strength or Cleave) in response to an opponent's reaction spell (like En Garde) during a showdown?

Ruling: You cannot play action speed spells in direct response to a reaction spell like En Garde because there is already a chain active. You can only react (not act) when a chain exists.

Sequence:

• You initiate showdown and gain Focus
• You can use Focus to play action spells at this point, or pass Focus
• If you pass Focus, opponent can use their Focus to start a chain (e.g., En Garde)
• You may react to the chain, but cannot play action speed spells since a chain is active
• After En Garde resolves, you get Focus back
• You can now start a new chain with action spells like Primal Strength or Cleave
• The showdown doesn't end until both players pass Focus in sequence

Nuances:

• When initiating a showdown, you gain Focus first and have a window to play actions before your opponent can respond
• Saying something like "move X to battlefield, any response?" is a shortcut for initiating the showdown and passing Focus
• You have multiple opportunities to use action spells: when you first gain Focus at showdown start, or after opponent's chain resolves and you regain Focus