Developer Insights: Arena with Kris Zierhut + Upcoming Arena Changes
Today we're getting some insight into the technical details behind how Arena drafts work in Hearthstone. Also present is information on changes coming to the Arena with Hearthstone Patch 11.2.
- We are adding new buckets that overlap halfway between the existing buckets. For example, a new bucket between buckets 2 and 3 will contain the weakest half of the cards from bucket 2 and the strongest half of the cards from bucket 3.
- There will be 6 new buckets for non-Legendary cards (for a total of 13), and 2 new buckets for Legendary cards (for a total of 5).
- Additionally, the strongest cards in the best bucket and the weakest cards in the worst bucket do not appear in the overlapping buckets, effectively reducing their rate of appearance.
Read on for the full Developer Insights: Arena!
Quote from BlizzardArena is fun. It can also be quite a challenge. If you’ve ever wanted to get into the technical details about how an Arena draft works you’re in luck, because today we’re pulling back the curtain on what’s happening behind the scenes when you build an Arena deck!
An Arena draft is the process of selecting the cards that will be in your Arena deck for a single run of up to 12 wins or 3 losses. You are offered a series of picks, where 3 cards are displayed, and you pick one. After picking 30 cards, your deck is complete.
The Arena Buckets
The picks are organized around the concept of card “buckets”. A card bucket is a grouping of cards according to specific criteria, including how often they’re chosen during a draft and how often they’re part of a winning deck. The buckets are currently comprised of seven categories of non-Legendary cards and three categories of Legendary cards. The buckets are organized by performance quality, regardless of rarity. For each pick, the game chooses a bucket by weighted-randomness (I’ll explain that a little later), and then pulls three cards from that bucket.
You may wonder how cards get organized into buckets. For each card, we know how likely a player is to win a game if that card is in their deck. Cards are organized by their win chance, with similar values grouped into the same bucket. For example, when this system launched in 10.4, all the cards in bucket 1 were cards with a win chance over 53%. There are a small number of cards in bucket 1, with the number of cards in each subsequent bucket increasing as the win chance declines. We also know how likely players are to pick each card. Cards with very high pick rates are “promoted” a bucket, such as Obsidian Statue, which moved from bucket 2 to bucket 1 in 11.0. While cards with very low pick rates are “demoted” a bucket, such as Fire Fly, which moved from bucket 2 to bucket 3 in 11.0.
Arena Card Weight
Many cards have an increased or decreased chance to appear depending on what type of card (spell, weapon, Class card, etc.) they are. That becomes their weight. For example, a card with a 50% increased chance of appearance would have a weight of 1.5. The chance for each bucket to be picked is proportional to the total weight of all the cards in that bucket. A bucket with a total weight of 200 would have twice the chance of appearing as a bucket with a total weight of 100.
We currently use the following modifiers to the weight of cards: A 100% increase for Class cards, a 50% decrease for neutral cards from the Classic and Basic sets, and a 75% increase for spells and weapons. Note that because spells and weapons are also Class cards, these two modifiers multiply, giving those cards a net 250% increase (2.0 * 1.75 = 3.5). There are no bonuses for cards from the most recent set. Additionally, the lowest quality buckets have a reduced chance to be chosen.
Micro-Adjustments – The Little Things
We like to have each Class close to equal in power level in the Arena. To accomplish that, we have a system that tries to even out the win rates of Classes, using a process called micro-adjustments. The micro-adjustment process is a holistic algorithm that evaluates the win rates of all cards that can be drafted in Arena. We typically apply this process a couple weeks after each expansion, once the initial meta has become clear. The algorithm gives each card a value between 0.7 and 1.3, and that gets multiplied by the card’s other weights. Because this changes the total weight of the buckets, this alters not only the chance for the affected cards to appear, but also the chance for each bucket to be selected.
Beyond the micro-adjustments, we also weight the selection of cards by rarity. Common and Basic cards are weighted to appear more often than Rare cards, which are weighted to appear more often than Epic cards. When there are a small number of cards in a bucket, the current system tends to let Rare and Epic cards appear more often than they otherwise would, which isn’t an issue in buckets with a large number of cards. We have improvements for this system planned for update 12.0 to help address that.
The Future State of Arena
We’re committed to exploring new ideas in Arena, keeping the experience novel and fresh, improving variety, and providing players with greater agency to make more interesting decisions. We’ve noticed that the variety of picks isn’t as diverse as we would like it to be, and we’d love to improve it. To achieve that, we’re making significant changes with Update 11.2:
- We are adding new buckets that overlap halfway between the existing buckets. For example, a new bucket between buckets 2 and 3 will contain the weakest half of the cards from bucket 2 and the strongest half of the cards from bucket 3.
- There will be 6 new buckets for non-Legendary cards (for a total of 13), and 2 new buckets for Legendary cards (for a total of 5).
- Additionally, the strongest cards in the best bucket and the weakest cards in the worst bucket do not appear in the overlapping buckets, effectively reducing their rate of appearance.
This change gives more cards a chance to be the best pick in their round, as they will be paired up against a greater variety of other cards. That will result in a more diverse selection of cards appearing in games and getting picked in any given draft.
We love the Arena, and will be sharing more about the work we’re doing to improve it now and into the future. Please keep the feedback coming, thanks for reading, and we’ll see you in the Tavern!
The semi-overlapping buckets is a really neat trick they're using, and I think it's great that they're sharing this info on their mechanics. Unfortunately, I don't think 1 weighting session per season is enough to even out the classes. After tweaking classes, there will be a different mix and another could come out on top.
But what I think should really be changed in Arena, is the discover mechanic. It ignores all rarities, drop rates and buckets. There's just too much to gain from these cards.
Okay, I feel like I might come to arena if these changes go through.
Now it seems a bit more sensible to me.
Man, I'm pretty disappointed with the "clickbait" aspect of this post. The picture had me thinking of some sort of change to the reward structure. Looking at the comments, I see I'm not alone. Just some food for thought for future posts.
Blizzard is always late. It would be great if they explained the process before Kripp explained on whatever information he had and he could gather.
They need to listen more to the players. Although it is good to get an insight into what happens behind the scenes for the players who are interested and play arena. I am sure this will be helpful to the ones interested.
Arena is even more clown fiesta than ranked. So nobody cares except Kripp and other streamers.
Going by rarity wasn't fair at all and rarity isn't an indication of power level, rather an indication of uniqueness of effect (or it's just arbitrary idk).
I think this approach is wrong. Buckets need to have more cards to choose to make drafting more important, not just more buckets. I think the existing buckets are fine but the available offerings should include a chance to offer cards from the top/bottom of the adjacent bucket so that deck synergy can be weighed against overall power of a card in draft selection.
people downvote but fuck whoever put that 12 win golden legendaries bait out there. that picture clearly implies change in rewards
Arena rewards rework when? :D
This is great information, and I'm glad Blizzard shared it.
I'm sure this gets asked a lot, but what I'd really like to see is an actual draft, where I open a pack, see some cards, pick one, and pass the rest. Maybe they'd have special draft packs, with a larger number of cards (could be 15, which would just be three normal packs). Or maybe they'd play in smaller groups? Options!
If we're adding a draft mode, with pods of people drafting together, you could even have it where the rarity distribution is the same as normal packs, and you open 6 packs (30 cards) for 750 gold. You'd keep the cards you draft, and get prize support as well. Rare drafting would be an option - you could take a Legendary card you want to own that doesn't help your deck, but then you wouldn't be likely to win.
There are a lot of other options and things to consider: what do you do about class cards in draft? Would you want a draft that offered you more than 30 cards, then a deck-build mode after where you put your best 30 together to make a deck? What if a draft player disconnects or quits?
I imagine there'd be an auto-pick after ten seconds in the event of DC - you might even see something like the rope going with every draft pick, but without the dramatic music. Regarding class, you could assign a class (hero power) based on what class you had the most class cards from - so you might take a few weaker Hunter cards in your aggressive deck to get the Hunter power. Or they could let you pick your class, regardless of the cards you selected, but that would have downsides. As for getting more than 30 cards, I really dislike being stuck with all 30 cards in the current version of Arena, and I'd love to get a few extra picks then "cutting" a few cards to make a deck.
Lots to consider, but I'm sure it could all be addressed. I, for one, would LOVE to see a Hearthstone draft in 2019!!!
Apart from the "keep the cards" aspect, this whole idea can be virtualized. Do all the drafting in a web app, and then copy over the deck code for the final product. And then pick subs for any cards you don't own.
Of course, it'd be much easier if it were a built-in game mode.
I'm hoping we get another fire festival and frost festival this summer. Those allowed me to not only save up a ton of gold for Frozen Throne's release, but also allowed me to experience arena without having to pay into it. I get that it's not that expensive if you're at least winning 3 matches in a run, but it's daunting to potentially give up packs for it.
Why do I say this here? Because posts like this remind me of how much fun is locked behind arena's entry fee. I only spend money on pre-orders, everything else in this game is f2p for me. I start saving gold pretty soon after a new expansion drops, spending gold infrequently for a pack here and there. The prospect of spending money on arena isn't appealing to me when I can engage the ladder and play consistent decks (which is a personal preference, not a "better or worse" statement), and the cost of an arena run - low as it is - stands as a deterrent to players like myself. I'm hesitant to spend gold on a series of matches I may hate and have to either play through to my 3 loss limit when I can just spend initial gold to get the cards I want/need for ladder and have more control over my experience.
A few more free arena runs a year could help me appreciate the changes and this mode in general a lot more.
if you are not playing constructed on all your region servers then do it like me and play for example arena on NA and constructed on EU. you can save up money for your packs on your main server and with the easier quest rewards you can play arena on a different server whenever you want :)
That's actually a really good idea! Never thought of that. Thanks!
Clickbait
Bucket system is a BAD idea,i miss old days of absolutely random draft when i got at least 5 wins every run.now it is EXTREMELY hard to get past 3 wins
Say it with me now
G I T G O O D
Damn you hearthpwn! I thought we're getting golden legendary as a guaratneed 12 wins reward =(
This system is so complex. They're trying to copy magic drafting, where you only get offered the most powerful cards a few times and the picking process involves other humans or AI, who take the other powerful cards from a pack before you get chance... This is closer to that in some ways, but a lot less interactive and more RNG.
That's okay but the layering of systems to try to address perceived problems is now pretty rediculous. Rarity buckets seemed fine to me, it was understandable. Then a bonus for each new set and class cards, fine. But balance between classes should've been done in design, not via micro(/massive) adjustments. And I still hate the extra spells and weapons idea. WTF? Making arena more reactive? We already have that. It's called constructed.
Please, don't take our deckslots?