How would one implement having a total set of TCG cards vs the specific instances of said cards in a player's deck, hand, field, etc?

Question

For example, let's say in total there may be 5 cards that are in the game, let's use:

Axe-thrower (3-cost, Creature, 5 Power, 3 Defense, Rush ability)

Ice Elemental (2-cost, Creature, 2 Power, 5 Defense, Crystalized ability)

Party Trick (3-cost, Spell, Swap the Power and defense of a single creature)

Blademaster (3-cost, Creature, 3 Power, 3 Defense, Gains +1/+1 for every other creature on the field)

Minefield (3-cost, Trap, Deal X damage to all enemies, where X is the number of creatures on the opponent's side of the field)

With those in mind, some have default values, which would be simple to store in the database, some would likely remain as 0's or another default value until their effects came into play, etc. Simple enough.

My question is more about how to handle the cards and their values once they're in decks, a player's hand, and on the field.

For example:

The Axe-Thrower is a 5/3 creature, but let's say it's buffed in some fashion - how am I differentiating an object which is the base version of a card, version the version which is modified in some way? The only values stored in the DB Would be the base values, not the modified ones, correct? Unless there was some kind of suspend functionality in which case I would have to track the modified values as well.

My initial thought of an implementation, at least for the Database side of things was as follows:

Cards (ID, Name) -- Base card

CardVersions (ID, CardID, Version, ImagePath, CardStatsID) -- Cards' stats dependent on version

CardStats (ID, Cost, Power, Defense) -- Stats for a given CardVersion

Now those would be the "base" cards, the following could be how the specific instances are handled?:

PlayerCards (ID, PlayerID, CardID, Count) -- Player's cards

Decks (ID, PlayerID, Name) -- Player's decks

DeckCards (ID, DeckID, PlayerCardID, Count) -- How many of a card in a given deck

Which is a decent start, I think, for the cards in a player's deck.

For the cards in a player's hand / on their field, would those all simply be references to the PlayerCards with objects that have modifiable versions of the stats? For example, a GameCard with Original Stats and Modified Stats, where the majority of the time, the Modified Stats will be the Original Stats to start, but will change as the cards are buffed or their abilities are invoked?

Am I missing a super-simple solution to this, what I would imagine, common case for TCGs?

Answer 1

If you carefully read the text of Magic: the Gathering cards you will notice a distinction made between cards and 'permanents' and 'spells'. When a card is in play, say representing a creature that has been summoned, it is not just a card but a permanent. Things that aren't cards - like ephemeral 'tokens' made by other cards - are ALSO permanents if they're in play.

From a computer implemention perspective I think of this as having two different levels. Cards have all sorts of statistics associated with them but are essentially static. Very few very obscure effects track the identities of actual cards themselves. Most effects affect permanents, which would come in a few types: those that are a card would be a CardPermanent which contains a pointer to a card and represents a physical card on the battlefield, while a creature token that is created as a 'copy' of another permanent might be a TokenCopyPermanent that contains a pointer to another permanent.

Effects mostly affect permanents. Permanents can be enchanted, destroyed, damaged, blocked, etc. The card inside is mostly unaffected, but for example if a permanent that contains a card is destroyed, the card inside goes to the discard pile.

Your hand contains plain cards. You can't have tokens in your hand or in your deck. When you cast a card it goes onto the stack, where it's a SPELL rather than a permanent, and again you can have effects that affect spells (countering them, copying them, etc.) and you can create noncard spells, although I don't think MTG calls them 'tokens' in this case.

This multi level approach separates things quite nicely and I have used it in an implementation of a subset of magic's rules. It seems to have covered everything I've needed to do so far.