Let's start with what the games I've covered in my history have in common:

• Players start with a deck of cards that they can create from their collection.
• Players draw cards randomly from their deck.
• Players invoke creatures, or minions, or heroes, and use them to advance their plan.
• Players take turns alternatively.

These seem to be the very basics of CCGs. Interestingly, I expected to have the resource system in this list, but Gwent broke that. I also thought there would be a combat system, but once again Gwent showed that it wasn't needed. Booster packs, well, they have to be the setting stone of a CCG, right? Nope, said Legends of Runeterra, while also doing very interesting things with the turn order.

Now let's look at what those games tried to do differently:

• The board varies from a simple list of cards to a map of tiles with each its own state.
• Combat between creatures, when it exists, always involves a strength and life points. However, games give varying flexibility in how creatures fight.
• The resource system generally falls into two categories: automatic (gain one resource each turn) or in deck (cards from your deck provide resources). Gwent is an exception (no resources) as well as Faeria (gain 3 resources each turn).
• The business model of games often has booster packs (except Legends of Runeterra), and that is often the primary way for a player to increase their collection. Most of the games are free-to-play, some are pay-to-play. However, all games include microtransactions, at least for cosmetic items.

The board design space has been explored a lot, from the flexibility of Magic — just put stuff on the board wherever — to the depth of Faeria and its "living board". There has been a lot of in-between, like Duelyst and Scrolls, as well as games I haven't mentioned like The Elder Scrolls: Legends, Spellweaver, SolForge or Infinity Wars.

Combat between creatures is often one of the central mechanics of CCGs, and as such it also has been explored extensively. In every combat system that I know of, creatures have a strength and some form of life points. Life can behave differently: Magic creatures' toughness is reset at the end of each turn, while Hearthstone minions' health isn't. Some game added a third attribute, like Scrolls' countdown (the number of turns until the creature attacks) or Spellweaver's speed (which determines how creatures can block). Most games have implemented various keywords and mechanics changing how combat works, like Magic's flying making creatures being harder to block, or Hearthstone's taunt forcing the opponent to kill the creature before they can attack you.

Resource systems have seen a lot of variations, and I think still have some room for innovation. There are three main characteristics that I find interesting: variance, linearity and restrictiveness. Let's take a closer look at each one.

Variance defines how luck drives when you'll get the resources you need. For example, Hearthstone has (almost) no variance: on turn 3, you'll have 3 mana, on turn 7 you'll have 7, and that never changes (except with a few cards, but it's really not common). On the other end of the spectrum, Magic has a lot of variance. There are chances, though generally small, that you do not even get a single land on your first turn. I believe that too much variance is generally bad, as it can create frustration in players. I also believe that having no variance at all is bad, as it forces you to create variance in other places to compensate, and that can lead to even worse frustrations. My hunch is that there is a balance to find, and I haven't played any games that have found it yet.

Linearity controls how the number of your resources evolves over time in a game. Hearthstone is perfectly linear: on turn X, you have X mana. Faeria is completely non-linear, as you get 3 mana each turn, but don't lose them between turns, so you can accumulate. One player might choose to use their 3 mana each turn, while another might not do anything for two turns and then cast a big card costing 9 mana. Magic's mana, being based on draws from a random deck, has a more complex linearity (based on hypergeometric distribution maths that I do not understand), but it tends to follow a somewhat logarithmic curve. Linearity is important because it controls the flow of a game. It is what allows games to have a story-like structure: early turns have cards of little impact, but as the game progresses players start using cards that are more and more powerful. The specific linearity of Magic is what allows it to have extremely strong expansive cards: you are never sure you'll get enough mana to play them. So you can build your deck to improve your chances, or you can take the risk of putting the expansive card in your deck anyway. But whenever you manage to play that expansive, powerful card, it's always a delight.

Finally, restrictiveness defines how hard to play you can make cards. The more restrictiveness your system has, the more control you have over the balance of your cards. Hearthstone, for example, has very little restrictiveness: cards have a simple, generic mana cost and a class. A card of a given class can only be put in a deck with the hero of that class. Then whatever the cost of the card, you know you'll have enough mana to play it eventually. Magic, on the other end, has fairly wide restrictions, thanks to its colors system. Cards require not only generic mana to be played, but also mana of specific colors — sometimes up to all five different colors. Given how the resource system works, it is very hard to put in the same deck a card that requires three blue mana and one that requires three red mana: it's unlikely that you'll have either three sources on turn 3, and even if you did, you would have to wait at least until turn 6 to be able to play the other card. (That is not exactly true because there are lands that provide several colors of mana, but it doesn't really matter for the sake of this argument.) I haven't seen a lot of innovation on restrictiveness: games either have something similar to Magic's lands (like Faeria, Eternal or Spellweaver) or they have something similar to Hearthstone's classes (like Legends of Runeterra, Duelyst or Artifact). I think there is room for some nice innovations here.

I'm not going to say much about business models, because even though I do think about them, I find it really hard to design them in a vacuum. So much of a game's business model depends on the game itself, and the company or team making the game, and the community, and many other factors that I have no clue about. I'll just say that I'm happy Faeria did things quite differently, and I'd love to know more about how it turned out for them, and that I find what Legends of Runeterra did is very elegant and user-friendly.

There is one last big thing that I want to talk about though. There's a thing that all the games I have mentioned, and many more in the CCG genre, have in common. And that is their theme. All of those games are about fighting against your opponent and killing them. Whether it's a fight between wizards, generals, heroes or planeswalkers, it is always about war or combat. I don't know of a single digital CCG that is not about fighting — though there are some in the physical space. Is it because those are competitive games, and war is a widely used setup for competition games? Probably. Does that mean a competitive game has to be about war? Hell no!

And this, I believe, is where the genre could innovate the most. There have to be mechanics out there to invent, or to draw from other genres, to replace the classic fighting system we've seen so much of. CCGs don't have to be about killing each other. They can be about culture, politics, science, trade, or so many other things. It is up to us Game Designers to tackle this challenge and bring innovation to the genre. Or at least, that's what I challenged myself to do with my own digital CCG, Souls.

And that is precisely what I'll talk about in my next, and last, article of this series!

Read the next part: Lessons learned working on my card game or go back to the introduction of this series.