Randomness in Card Games (Magic + Hearthstone)

The inspiration I had for this article was comparing and contrasting early format reviews from content creators in both game. One of the other interesting points I noted (though ultimately backed away from) was that recently Magic had the tendency to be “solved” much more quickly.  High powered cards would come out that would create degenerate decks.

What this article morphed into, however, was something entirely different.  A compare and contrast at how two of the most popular card games in the world deal with things like shaping player behavior, handling randomness, and properly costing abilities.

A quick note: Before moving forward it’s important to understand that I’m not discussing a particular format (like Limited or Constructed) but rather the broader ruleset that both game exist within.

Structural Effects


Magic: the Gathering and Hearthstone are both card games in which players build a deck of some number of cards, to battle one another typically within duals although sometimes in other ways as well.

Both Magic and Hearthstone rely on a system of mana which defines how much a player has to commit in order to cast a given card.  Both games restrict how much mana you can develop on a single turn (1) in order to create a sense of progression across the game. Both games restrict the range of cards that any single deck has access to.


Mana System

Magic’s mana system depends on the cards you put inside your deck.  Each turn players have the opportunity to play one land card (lands produce mana), but may do so (once per turn) as long as they want for the remainder of the game.  Hearthstone gives you a single mana for free (in the form of crystals) every turn up to a limit of 10.

This key difference sets up the main structural contrast between the two designs.  Hearthstone’s rules lead to increased certainty, where Magic’s rules lead to decreased certainty.  For example, on turn 10 in the average game of hearthstone, you will probably have 10 mana crystals.  On turn 10 in the average game of magic you will probably have between 6-8.

This lack of certainty changes the types of interactions that players can have and the types of cards that game developers will design for.  Whereas developers of both games have to price tempo into every cost (a card that costs 6 will have to wait 5 turns before it can be played), developers at magic have to price the uncertainty cost into the card as well.

Deck Construction

Magic has a minimum deck limit of 40 (for limited) or 60 (for constructed) with a maximum of 4 unique cards per deck.  Hearthstone has a minimum (and maximum) of 30 cards with 2 unique cards (1 unique “legendary”) per deck.

Hearthstone’s decksize can afford to be small because it doesn’t have to fill any slots with lands (to produce mana), but that means the unique card restriction has to be tighter.  If it were as high as magics, the average deck would probably have 8-12 instead of 15-20 unique cards which would push the game past a tipping point in terms of regularity of play.

While in terms of cards that impact the game state they are roughly the same (the average magic deck will have 34-36 spell cards and every hearthstone deck will have 30), the impact on the flow the game is rather different.  For example, when drawing cards, any given card in magic could be a land (which I’m going to describe as roughly “non-impacting”) whereas every card in hearthstone has an impact on the game state.  This further reinforces Magic’s trend towards randomness and Hearthstone’s trend to similarity.

The other main deck construction restriction is the classes of cards that can be put in a given deck.  In magic, this is defined by the restriction of “color costs” or certain requirements every card has about the types of mana (of the 5) that *must* be used to pay for that card.  Hearthstone has a hard restriction, in that there are certain types of “class” cards (9 classes in total) that can only be played by that class.

In Magic, this means there is the potential for greater similarity for which cards will show up in decks, as the only restriction a player will have is the probability that they can cast it to affect in a game, but more randomness in game, where it’s possible to simply not be able to cast a card you put in your deck.  In Hearthstone, it means there is more randomness across decks (playing a Paladin v. playing a Mage will necessarily look very different).



The other main separation between Magic and Hearthstone is the combat system.

Hearthstone is an attack-advantaged system, where the attacker gets to determine which defending creature (or player) to attack, with some restrictions.

Magic is a defense-advantaged system, where the attacker may only attack another player or player’s planes walker, and the defender gets to choose which creatures they wish to block with.

The second point of difference is that Magic has “instants” or special spells that can be played on an opponents turn, whereas Hearthstone has “secrets”, or traps that you play on your turn but can be triggered by an opponents actions.  While both of these can have non-combat effects, I want to focus on their combat impact, as it is the largest differentiator in how the games end up being played.

Hearthstone players are continually being incentivized to attack, which tends to bring the game to its conclusion more quickly.  There is smaller downside to attacking your opponent with your awesome creature because you can see what traps they have laid, and you get to decide which creature to attack (if any).  In Magic, you have to offer your creature up to attack, and then math out potential blocks as well as cards that your opponent might have in their hand.  Board states where 3 or more creatures are in play (in Magic) for both players can be challenging to puzzle through, whereas similar board states in Hearthstone are easier because the direct outcome is much more apparent.

Edge Conditions

There are a few other wrinkles that Magic and Hearthstone have that I wanted to nod to but didn’t feel the need to describe as part of an overall pattern.

Magic has the “planeswalker” card type which is a unique card type that remains on the field and can be interacted with by the opposing player.  Hearthstone has a unique ability for each class, that can impact the game efficiently.

Each game also has different “empty deck” conditions.  In Magic, if your deck runs out and you would draw a card, you lose.  In Hearthstone if your deck runs out and you would draw a card you take increasing amounts of damage until you run out of health.



Magic is a game with more uncertainty that tends to lead towards more static states.

Hearthstone is a game with more certainty that pushes towards more end states.

While the easy conclusion to draw might be something along the lines of “Magic is more random and Hearthstone is less random, therefor Hearthstone is a more competitively balanced game”, that is not at all what I’m saying here.  In fact, you’ll have noticed I haven’t actually talked about any of the cards in either game.

Once you start looking at the cards, the design decisions become very apparent.  Given that Magic is a baseline more random games, more of the cards in Magic tend to lead towards a more certain, stable game state.  You’ll see effects like cycling (draw a card), searching your deck for needed land or spells, or using a graveyard as a resource.  These are all systems that developers use to allow players to exert control over the game state.

In Hearthstone you see the opposite.  There are many cards that rely on the easy random number generator a computer provides to inject more randomness into the game.  Mechanics like Discover pull cards out of pre-determined subsets for players to choose from, or will pick opponents cards at random to impact, or secrets where you play out the spell, but your opponent actually can intuit when to trigger it, thereby reducing your own control.


What this says perhaps, is that each game has different balance challenges that the other doesn’t have to deal with.  Because in magic so much of the game is about giving control back to the player, it is often easy to break the game in ways that make certain impacts too easily repeatable on a card by card basis.  Combos that only require 1 or 2 cards can become degenerate simply because it can be difficult for the developer to know how far down the “control” spectrum to push a card.  For example Aether Marvelworks was an issue, because all it really asked a player to do was to have that card, and also another dominant card in their deck.  The rest of the deck could be dedicated to pulling that effect off.  Whereas for Magic 3 card combos are relatively safer because assembling them in a timely manner can become a bigger challenge.

Hearthstone has an opposite problem.  Because so many cards rely on somewhat random effects, repeatable effects that happen across multiple cards can become especially dangerous.  For example, Jade Druid was an issue because a few cards were able to utilize that mechanic and build off of one another to powerful effect because cards would show up with a fair measure of reliability.

What the inspection really revealed to me however, was that even though both Magic and Hearthstone are built on very similar underlying systems, their implementation leads to different game states and different challenges that each development team has to solve.


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