You can take turns drawing cards from your deck and putting them in your hand… but at the moment all that leads to is a hand full of cards. Sounds like we need a way to start playing cards from our hand toward some other purpose. In this lesson we will provide the ability to play a card, and also enable the local player to control which of the cards they wish to play by interacting with what is presented on screen.
In the last lesson, we implemented the Fatigue stat – caused by attempting to draw cards from an empty deck. However, although we could watch the stat change, it had no real effect on the game itself. In this lesson, we will add a reaction to fatigue which applies damage to the player’s hero by the fatigue amount. As a result, we have the means to determine when a game will end – whenever a hero’s hit points have dropped to zero.
In the previous lesson, I mentioned two cases where drawing cards should not be allowed: when your deck is empty, and when your hand is full. In many cases an exception to a game action could result in the complete cancellation of the action, but what if the action could be partially performed? For example, imagine that you needed to draw three cards, and only had two in your deck. Rather than cancel the entire action, you should still draw the two cards that were available, and then apply fatigue for the third draw attempt only. Let’s try it out.
One of the most powerful features of the Action system is the way it can chain together actions with reactions into a long sequence of events. At the moment we have only implemented a single action – changing turns, but in a game like Hearthstone, this action will always have at least one reaction. When a player starts their turn, they are supposed to draw a card. Let’s go ahead and implement the draw a card feature as a reaction to the action for changing turns.