It's ok
It very nice, but some things need work. For instance, the archer always seems to attack the greatest threat on screen rather than the closest. This is not good because the player will typically target the greater threats manually because the archer cannot destroy them quickly enough. As a result, the castle is swarmed by weaker and faster units until the before mentioned threat (such as a battering ram ) is dealt with. Also, the mage seems more or less useless. In the time it takes to activate and cast a spell, the screen becomes swarmed with enemies. When combined with the previously mentioned fault you get a screen full of weak fast moving enemies waltzing directly to the castle with minimal resistance. This essentially encourages the player to completely disregard magic and make up for it with rapid clicking.