foo.fs

let rec TakeAction (gs:GameState) : bool =

    // -snip-

    // Not sure which card to choose, so let's try them all!
    // `None` represents not imprinting a card.
    // Stop if a possibility wins the game (`List.exists` will short-circuit).
    None :: (gs.Hand |> Seq.distinct
                     |> Seq.map (fun card -> Some card)
                     |> Seq.toList)
    |> List.exists (function
        | None ->
            log "Entering hypothetical: nothing was imprinted."
            TakeAction gs

        | Some imprint ->
            let imprintColor = Color (Cost imprint)
            log (sprintf "Entering hypothetical: imprinting %s for %s."
                            (CardLabel imprint) (ColorLabel imprintColor))
            let hypotheticalGameState = gs.Clone()
            hypotheticalGameState.Hand <- RemoveOneCard gs.Hand imprint
            hypotheticalGameState.Moxen <- (imprintColor, false) :: gs.Moxen
            TakeAction hypotheticalGameState)