Before we dive into the gameplay, it's interesting to note that Hearthstone is fulfilling several 'firsts' for Blizzard. It's their first game from a small team — in fact, it began as an unofficial project from a group of devs who just loved the idea of making a CCG. It's their first free-to-play game; they have a reputation for blockbusters that take years and years to develop, whereas Hearthstone's turnaround time seems much quicker. It will also be their first mobile game, as they have plans for iOS and Android ports later in 2014. It's nice to see from a company that's mostly been riding its old IPs for the past 15 years.
Now: on to the gameplay. One of the game design themes Blizzard is known for is their insistence on building games that are accessible to a large number of people. Diablo 3 smoothed most of Diablo 2's rough edges, and World of Warcraft came to dominate that MMORPG market in part because it eased many of the soul-crushing antics of Ultima Online and EverQuest. The mantra they often repeat is: "Easy to learn, difficult to master." Their preference for accessibility is very much alive in Hearthstone.
At the start of the game, you're given a hand of three cards. If you don't like any of them, you have a one-time chance to exchange one, two, or all three for random replacements from your deck. Whoever wins the coinflip gets to go first, and the play who lost gets an extra card to compensate. Once you've started, you alternate turns, casting spells and summoning minions to fight. You also have an avatar that can perform an action every turn, if you have the resources for it.
Almost all CCGs have a resource pool of some kind, and Hearthstone's is simpler and more straightforward than most. Spells are cast with mana. Every turn, you have your maximum mana pool increased by one, up to a total of 10. You don't have to worry about drawing too many or too few resources, and you don't have to worry about drawing the right type of resource. Each spell has a simple numerical cost, and you can cast as many spells as you can afford. Your mana pool refills to its max every turn.
The mana system has its pros and cons; it's quite common in games like Magic: the Gathering to lose games because you had bad luck drawing mana, and Blizzard's system removes that. It's also very easy and intuitive for players who are new to the game or to the genre. Unfortunately, it also cuts down on how clever you can be with resource management, both in gameplay and during deckbuilding.
It limits the diversity of the card pool somewhat — without resource cards, you don't have resources that behave in different and unique ways, or those with a dual purpose. It also alters the pool of viable decks. In Magic, there's a definite cost to running decks that are 'greedy,' trying to run too many different colors or too many expensive cards. Hearthstone doesn't have that constraint. Whether you consider it a pro or a con likely depends on your playstyle.
Now, as I said earlier, you use all this mana to cast spells, summon minions, and fire off your avatar's ability. It's important to note that all of this happens on your turn -- this is another of Hearthstone's significant steps toward accessibility.
One of the most important rules concepts with most CCGs is the idea of priority. If two players both want to take an action at the same time, who gets to do it? Well, the player with priority. This is something that's very easy to deal with in real life, to the point where it doesn't need to be explicitly mentioned at all. But when you move a CCG online, things get much more complicated and cumbersome. For example: turns in Magic: the Gathering are comprised of a series of 12 steps and phases. Certain spells can be cast at any time, so in each of those steps and phases, both players have to decline to cast anything, which is called "passing priority" to move onto the next.
In real life play, there's an implicit understanding: "stop me if you have something to do." A turn can be as quick as drawing a card and saying, "Go." When you take the game online, the game client can't make assumptions like that, so you're left explicitly passing priority for every step and in response to every play your opponent makes. Magic's online client has some shortcuts to deal with this, but to even use them requires an understanding of the rules that is far beyond new players to the game. Even for experienced players, it's a pain in the ass, and one misclick out of the dozens or hundreds you make in the course of play could cost you the game.
All of this was a non-starter with the developers of Hearthstone. Remember: they prize accessibility. So they made a simple choice: players can't do anything if it's not their turn. With this single decision, they eliminate 90% of the difficulty in learning a CCG. This, too, comes with a heavy cost. Being unable to respond to your opponent's actions dramatically cuts the potential scenarios in a game, and the kinds of cards they can implement. The complexity created by actions you can cast at any time are the meat and potatoes of even simple Magic: the Gathering decks.
But let's be clear: Hearthstone isn't trying to be Magic: the Gathering. While there will certainly be some overlap between the playerbase of each game, Hearthstone is deliberately trying to bring CCGs to a wider audience. Probably a younger audience, too. The graphics certainly lend credence to that idea. The in-game UI is the perfect example of Blizzard's relentless devotion to polish. The UI is really well done; everything's quite intuitive, and each action you take, be it casting a spell or just ending your turn, has a weight, an impact to it. It blows Magic's online client out the water, that's for sure.
There's more to the game than just building a deck and duelling -- there's also Arena mode, which is similar to what's called "drafting" in other CCGs. In the Arena, you pick a class, and then you're shown three cards of roughly equal power levels. You select one, and the other two are discarded. You repeat this process until you've made 30 picks, and that is your Arena deck. Then you face off against other players who built their deck the same way.
I like the way they did this -- there are a lot fewer cards to pick from, but each pick is meaningful. In Magic: the Gathering drafts, you have up to a full pack of 15 cards to select from, but even then there are sometimes only one or two picks that are remotely viable. For all the complexity that was lost by Hearthstone's other choices, this mode retains as much as it can.
Unfortunately, it's also the mode that sometimes costs money to play. It's $2 to enter, or the equivalent amount of in-game gold, which you can acquire without spending money if you have the time. This is a pretty typical CCG business model, and it's actually a lot cheaper than your typical CCG draft. But there will be many, many people who end up nickel and diming themselves for more than they usually spend on a game. Oh, I should add that you do get prizes for playing, and if you win enough, the draft pays for itself. Most people can't do that on a regular basis, though.
You can buy packs of cards as well, though just buying them and opening them isn't the most efficient way to do things. Since there's no card trading between players in Hearthstone, Blizzard implemented a new feature that's impossible with cardboard games: crafting. If you have a stack of useless cards, you can melt them down into components, which are then used to create the cards you want. It'll take some doing to get the really rare ones, but it's entirely possible to get the cards you want without dumping a bunch of money into the game, and that's a nice option to have.
The crafting UI, along with the collection and deckbuilding UIs aren't quite as slick as the gameplay UI, but they're tolerable. It's not a very powerful interface, but that's a side effect of designing for simplicity and accessibility. One thing I will say is that Hearthstone is probably the first PC game I've played where I've thought, "gee, this would be pretty nice to play on a tablet."
There's another interesting aspect of Hearthstone I want to mention. CCGs have always been social games. A big part of the fun, for a lot of people, is sitting down across from somebody else and playing with them. Even for players who aren't looking for that interaction, it's engaging to try to mislead your opponent or figure out when they're bluffing. Hearthstone, by contrast, tries to strip out most of that social interaction. There's no in-game chat, and no chat channels -- your only interaction with your opponent will be a few emotes and the gameplay itself. It makes for a curious effect.
There's an AI built into the game, but even when playing against humans, it kind of felt like I was playing against AI. On the other hand, I could certainly see myself firing it up on tablets with other people in the room and playing that way, even though I'm not much for mobile gaming.
Collectible card games are doing better than ever, and it's reasonable to expect digital ones to grow and thrive as well. With Blizzard's fanbase ready to jump on board, I have no doubt Hearthstone will be quite popular. Players looking for a Magic: the Gathering clone in a Warcraft universe will be disappointed. Players demanding a certain level of complexity will also likely tire quickly of Hearthstone. I count myself in this category. That said, it does a very good job at doing what it's trying to do, which is to be a fun and accessible digital CCG. It'll be great for introducing people to the genre.