CardState.cljs

(defn card [card-state]
  (letfn [(handle-card-click! [event]
            ; pair of cards was revealed, now let's go for another pair step
            (if (= (revealed-cards-count) 2)
              (hide-nonmatch!))

            ;reveal next card in step
            (reveal-card! card-state)

            ;if 2 of cards are revealed, we have to check parity
            (if (and (= (revealed-cards-count) 2)
                     (= (:last-symbol @state)
                        (:symbol @card-state)))
              (mark-match! (:symbol @card-state)))

            ;let's remember last symbol to make comparison in subsequent steps
            (swap! state assoc :last-symbol (:symbol @card-state)))]

    [:div.card
     {:onClick handle-card-click!
      :key     (.random js/Math)
      :class   (if (@card-state :matched)
                 "card-matched"
                 "card")}

     [:span.card-value
      {:class (if (@card-state :visible)
                "card-value"
                "card-value-hidden")}
      (:symbol @card-state)]]))