Last In First Out – How the stack works.

Contrary to the ‘tip’ yesterday, the stack does in fact exist and with respect to the rules knowledge of it and how it works can be helpful in figuring out the game state. This knowledge is useful when making strategic decisions and can help win games too.

One of the stack’s basic aspects is the order that items placed on the stack resolve. The stack is often compared to a stack of plates or other objects, where you add to the top of the stack and ‘deal’ with the one on the top. In other words the most recently added item added to the stack will be placed on top and when resolving spells and abilities the last added to the top will be applied first. The phrase and acronym of Last In, First Out or LIFO is used to describe this.

For example, if a Runeclaw Bear was is targeted by Shock. If the controller of the Bears were to respond to this Shock by playing Giant Growth, then the stack would look like this:

Giant Growth

Because of LIFO, the Giant Growth will resolve first, and make the Bears a 5/5 creature. Then when the Shock resolves, the 5/5 bears will receive two points of damage. Because this Bears will not receive lethal damage and remain in play.

Let’s take this situation and assume that the order that these two spells were played is reversed. If so, then the Shock would be on the top of the stack and resolve first. When it does the Bears will receive two points of damage. Immediately after this spell resolves, state-based actions are checked and this Bear will go to the graveyard as it has received lethal damage. Then when the Giant Growth attempts to resolve, it will become countered on resolution as its target is no longer in play.

(Yes, this rules tip is rather basic for experienced players, but I really want to make sure that everyone realizes that yesterday’s post was a joke.)

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