The interesting thing to me is what exactly Blizzard Entertainment said that prompted the author of this blog post (a Google research lead) to decide not to release the utility that at Defcon he said he would.<p>Excerpt:
"Following Defcon we had a series of conversations with the Hearthstone team about our research... they were very concerned that our real time dashboard that can predict your opponent’s deck will break the game balance by giving that person (that is, whoever has the tool) an unfair advantage. They also expressed concern that such a tool..."<p>There's no evidence his utility was derived from reverse engineering or a TOS violation. It appears to be based on evaluating a large number of Hearthstone matches and using those results to create a mathematical model that lets you find "undervalued" cards. One application of the model is a utility that can help to predict "what your opponent is going to play based on previous turns." <a href="https://www.elie.net/blog/hearthstone/how-to-appraise-hearthstone-card-values" rel="nofollow">https://www.elie.net/blog/hearthstone/how-to-appraise-hearth...</a><p>Blizzard has taken aggressive legal action before. As EFF tells it, Blizzard filed "a DMCA lawsuit against a group of volunteer game enthusiasts who created software that allowed owners of Blizzard games to play their games over the Internet. The software, called "bnetd," allowed gamers to set up their own alternative to Blizzard's own Battle.net service." <a href="https://www.eff.org/wp/unintended-consequences-under-dmca" rel="nofollow">https://www.eff.org/wp/unintended-consequences-under-dmca</a><p>This time, I wonder if the decision not to release the utility was prompted by a friendly query from a Blizzard developer or a C&D nastygram by a Blizzard attorney -- with a lawsuit threatened if he didn't comply.
It might be easier to use machine learning for card prediction in Hearthstone than you might think at first glance: the problem space is constrained by class choice, metagame, and limited card pool.<p>If your opponent is using a Hunter deck at a reasonably high level of play for example, he's using one of <i>two</i> deck types, and due to Hearthstone's 30 card deck limit, there are a finite amount of bombs he can put into the deck.<p>Contrast this with MtG decks: although you might know the overall archetype of the deck, the problem space is much larger, and much more likely to have tiny variations, especially in the number of card copies in a deck (Hearthstone only allows 1-2 copies of one card a deck; MtG allows up to 4, in addition to any number of basic lands.)
Modeling cards as independent and linear is a vast <i>vast</i> oversimplification. It doesn't account for card synergy, exhausting your opponent's counters, managing your mana curve, managing your hand size, etc.<p>For example, Shadowstep is an alright card... until you combine it with Leeroy Jenkins. Then it's 6 damage for 2 mana, and basically the reason Miracle Rogue decks exist.<p>Linear and independent is a reasonable place to start, but nowhere near the goal.
As someone who has played quite a bit of Hearthstone, I wish he had released his machine learning tool, even though I probably wouldn't use it myself. Such a tool would basically punish people who copied a pre-existing popular deck verbatim, and reward people who creatively designed their own decks to be different from the mainstream.<p>I think it's worth mentioning that high level players can already do a pretty good job of predicting the cards in peoples' decks. The best players will often experiment with modifying existing decks or building their own from scratch, partially because there's a significant advantage to not using a popular deck that your opponent already knows how to anticipate.<p>Hearthstone has a funny kind of a sandwich pattern, where the best and worst players tend to create their own decks, but the vast majority of the middle is largely dominated by the same few decks that you'll see over and over again. It would be nice if a tool like this could help break that pattern.
Cool initial look at the problem space. I think a Nash HearthStone deckbuilding solution is very possible, but it's the definition of building to one client given the aggressive legal stance Blizzard tends to take. The best commercial chance would be to try to sell it as a balancing tool so devs could make sure all classes stay viable for new releases. Given board + life + hand information is clear, alpha beta for the gameplay strategy combined with a simple genetic algorithm for deck peturbation, initialized with the best decks from current players, could probably be superhuman competitive.
Card value calculation should look not just at mana but also at the card itself as a cost. Something like Wisp might be great value/mana but it's appalling value/card. That's just obvious and simply to fix. Keep in mind the Warlock hero power(2 mana and 2 self hero damage to draw a card) as a reference point for the value of 1 point of 'card'.<p>The worst error, I think, is the the assumption that points increase linearly in value. Hearthstone has clear thresholds of usefulness. You'd almost always want to draft a 4attack/5hp for 4 mana creature, you'd rarely want to draft a 5attack/4hp for 4 mana creature, despite their model valuing 1 point of attack at .57 and 1 point of hp at .40.<p>For instance their Estimated cost for Light's Justice is 2.6 and for Fiery Waraxe 2.5. Except Light's Justice is godawful and Fiery Waraxe is one of the best cards in the game.<p>Why? Because Fiery Waraxe will kill almost any 1, 2, or 3 mana drop(most of those creatures have 2-3 hp). Light's Justice will tickle them and cause you to take massive amounts of damage.<p>It's also the reason Chillwind Yeti(4 attack/5 hp) is a 100% pick in Arena drafting(where you tend to build non-gimmicky general value decks). It very very often trades 2 for one and results in card advantage, without needing any combos. The increase from 4hp to 5hp is much more important than the increase from 3hp to 4hp.<p>Overall I really liked their experiment, despite disagreeing with their method/results :)
He mentions that he wishes Replays were added to the game for statistical analysis purposes. As someone who has dealt with the problem space at hand, I cannot agree more. Replays are something cheap that really should be added to the game.<p>Can't be that hard - Hearthstone uses Protobuf internally. I hope we can get something like that soon; whenever a game becomes popular, I weep at the amount of analysis and research that could be done on it but is not due to lack of public analytics.
Well, looking at the video, 11mn in, i see a weird system simplification:
* 6 = 6a + 7h + i
* 4 = 4a + 5h + i<p>get "reduced" to:
* 1 = a + 1.16h + i
* 1 = a + 1.25h + i<p>I wonder why it isn't i/6 and i/4... basic mistake or I missed something?