Saturday, 25 October 2014

The Value of Choice in Game Design

Choice has value, but it’s not always possible to quantify. This allows a game mechanics to be recycled. Consider the following three cards in Magic: The Gathering.

1. Lightning Bolt - A spell to deal 3 damage to a creature or player once, and at any time.
2. Kird Ape - A creature with 2 attack and 3 defence, as long as a certain easily attainable condition is met, and worse otherwise.

3. Vexing Devil - A creature with 4 attack and 3 defence, but the opposing player may choose to take 4 damage immediately instead of having this creature enter play.


All of the cards have the same requirements to be played (one red mana). There are differences in the years between when each card was tournament legal, but all three cards are considered better than the typical card. In short, all three of these cards are highly interchangeable in a deck. So which one is the best?

Case I:

If the opposing player allows Vexing Devil to come into play, it has more attack than a Kird Ape would, so it's better than using a Kird Ape in that situation.

Case II:

If the opposing player does NOT allow Vexing Devil to enter play, then the opposing player takes 4 damage. This is more than the 3 damage than a Lightning Bolt would deal.

In either case, it seems like Vexing Devil performs better than either card. What makes these three cards fairly comparable? The opponent's choice does.

From the player of Vexing Devil's perspective, they will always end up with the least favourable of the two cases. If either one of those cases were as good as the two alternative cards mentioned, the alternative card should be used instead. So, to make Vexing Devil viable, both cases must be better than those on alternative cards.

From the opponent's perspective, they can choose to let the creature come into play only when they can deal with it in a way that is less costly than taking 4 damage.

In short, the value of choice must be priced into the relative strength of game elements. This is what makes the Queen in chess strictly better than either the Rook or the Bishop. The Queen can only make moves that either the Rook or the Bishop can do, but having the choice to do either is what gives her her power.


Consider one more card:

Forked Bolt – Deals 2 damage to target creature or player, OR 1 damage to each of 2 such targets.

This card is also considered above-par, and has the same mana requirements as the other three. It's arguably weaker than Lightning Bolt, but not by much. Why? The player of this card has the additional choice of splitting the damage.

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