339. The State of the turn is partially determined by whether or not a Showdown is in progress.

339.1. The turn is said to be in a Showdown State if a Showdown is in progress.

339.1.a. Cards of all Categories, by default, cannot be played during a Showdown State.
339.1.b. Card abilities, by default, cannot be played during a Showdown State.

339.2. The turn is said to be in a Neutral State if no Showdown is in progress.