Why revealing all is the secret of Slay The Spire’s success

This is The Mechanic, where Alex Wiltshire invites developers to discuss the difficult journeys they underwent to make the best bits of their games. This time, Slay the Spire [official site].

Slay the Spire is a deck-building card game about careful attack and defence. And poisoning. And letting your own blood to amplify your damage, and hitting each enemy every time you lose a card, and gaining energy by hovering close to death. It’s a bit like Hearthstone, but it’s also a Rogue-like in which you ascend floors and find new cards and relics which power up your character in transformational ways.

It’s really good! And the secret behind it is a detail that seems minor, but without it your card-playing strategising would be for nothing. It’s the fact you get to see what your enemies will do on their next turn.

Slay the Spire knows that fun lies in certainty. It shows you what damage the enemy will do next and how many attacks they’ll make, or if they’ll defend or cast buffs on themselves or cast debuffs on you. Knowing what’s going to happen next opens a space in its randomness and permadeath from which you can make plans.

But it wasn’t part of developer MegaCrit’s original vision for the game. Back then, programmer Casey Yano and designer Anthony Giovannetti were focused on fusing a game like Dominion, the card game which probably founded the deck-building genre, with the Rogue-like.

This is what one of the first prototypes, from September 2015, looked like. A lot of what Slay the Spire is today is right there, from the names of its basic cards, Block and Strike, to its core energy design and map. But there was a problem. “Enemies were very random and we had no idea what they were going to do,” Yano tells me. “The difference between playing a defensive card against an enemy attacking versus playing an attack was all a guessing game.”

”Yeah, so a big part of it is that if you’re playing a JRPG it doesn’t really matter what an enemy is about to do a lot of the time, you’re just going to attack or cast your high-damage spell and you don’t really care what they’re going to do,” says Giovannetti. “No one uses the defend function in a JRPG.”

There’s a big difference between RPGs and Rogue-likes. In RPGs you can try out fights, often able to escape if they’re too hard or to reload a save if you die. Then you can grind a little so you can come back again and beat it. “In an RPG a battle is not life and death,” says Yano. But in Rogue-likes you’re always on your toes, tense with the awareness that if things go badly, they’ll probably screw up your entire run. And Slay the Spire’s earliest incarnation featured too many random attacks, the kind that are fine in an JRPG, but for a Rogue-like they were punitive.

“We needed to find out a way of seeing what the enemies are doing,” says Yano. Their first attempt was a system they call Next Turn. They placed a bar at the top of the screen which shows off player and enemy health bars and other information, and also a line of text which described what the enemy would do next. Here’s what it looked like in a prototype from March 2016.

“I don’t know if any turn-based game had done that before,” says Giovannetti. “We felt it was interesting, it was going somewhere. I actually had context to decide if I needed to defend up or go all-out.”

It’s fascinating that Slay the Spire should appear just as Into the Breach comes out, because Into the Breach, a Rogue-like tactics game from the makers of FTL, is also founded on players knowing what their enemies are going to do next. Yano and Giovannetti are big FTL fans but they didn’t know many of the specifics of Into the Breach until I told them about them. “I try not to look at unreleased games because I feel like it ruins the magic a little bit,” Yano says. ”The FTL guys and us are very similar people, I think.”

This new interest in showing enemy intents seems to me like it might be product of the way the fundamentals of the Rogue-like are being teased into new shapes, such as a card game, or Advance Wars-style tactics. And they show how their developers recognise that Rogue-likes were always founded on a strong dose of determinism. Think about playing Brogue and how, with experience, you can always make strong assumptions about what’s going to happen on the AI’s next turn because you can see everything around you. The magic lies in the complexity of the interactions between each little deterministically driven cogwheel, and your ability to use them to your advantage.

That’s exactly what Slay the Spire trades on, too. But the Next Move system brought up problems. ”One of the major ones was that when there were multiple enemies, what were we going to display at the top as the next move?” says Yano.

“We couldn’t have multiple enemies without it working badly,” says Giovannetti. “You could click on an enemy and that would change what you could see, but it was a big pain in the butt.” Playtesters continually played cards on the wrong enemy because they hadn’t selected it, and they had to click on each one to see what it was going to do.

“It was a pain in the ass,” says Yano.

And yet the way the enemy’s move was described in text allowed a lot of dynamism and nuance to what MegaCrit could have them do. They could introduce different states in each turn, so, for example, there could be a temporary situation in which if the player did precisely seven damage to the enemy it might trigger a special effect, all communicated through text.

But the Next Move system was so awkward that they had to drop it. MegaCrit were anxious that everything in Slay the Spire was visible at a glance, which would make it both easy to play and streamable. “We had to make some sacrifices,” says Yano. So they moved to a system that used always-visible icons, which couldn’t communicate as much nuance. “But usability improved so much that I don’t think we have any regrets.”

Megacrit had created the fundamental design that the game features today, and they call it the Intents system. But it took them a while before they were comfortable with it going all the way with showing what’s happening next. The very first iteration seemed to turn the game into a game of maths. While they wanted it to be transparent, they didn’t want players to be drowning in information. Having them add up attacks to figure out how many block points they needed to counter them seemed to go too far and they worried that players might be put off if they thought Slay the Spire was simply about numbers.

They were also dealing with implementing a big change to the game. Of the duo, Giovannetti is the card player (for proof, he runs Stimhack, a major Android Netrunner fansite and forum), while Yano isn’t so much. In fact, Yano describes himself as a rather impatient player, and he enjoyed the flow-state he got into while spending hours each day playtesting the game. Without precise numbers, he’d block-attack-block without thinking hard. “But when we introduced numbers, we felt they prevented you from getting into that. Change is always a rough thing,” he says.

“Yeah, it felt dramatic to us,” says Giovannetti. “Definitely in hindsight it’s correct, but when we were making it, it was a little concerning because we had been breathing the systems.”

“It’s unknown territory, because in every single game that does turn-based combat I knew of, the enemies’ intents are never revealed,” says Yano.”

So they came up with a halfway house, where attacks were indicated by symbols. A little sword meant the the enemy was going to deal between zero and five damage. A bigger sword was 5-10, a scimitar was 10-15, a butcher’s knife was 15-20, 20-25 was an axe and 25-plus was a scythe. They hoped the uncertainty within each bracket would prevent players from getting lost in the numbers. “But it was actually worse and required more thinking!” says Yano. “There’s only two of us and we didn’t have enough testers, so we were a little delusional.”

“The damage range made it like, ‘Does it mean the enemy is doing random damage? Do you have to be probabilistic about it?’ So that made people put people into more analysis paralysis,” says Giovannetti.

So they tested a version with precise numbers on their most engaged playtesters, who had hundreds of hours of experience with the game, and they saw them immediately take to it. And it didn’t affect their performance at all. It turned out that they’d already pretty much memorised every number. By exposing the actual attack values, all Megacrit had done was to unburden the players of having to remember them.

“That was another good sign, right, that if you get good enough then hiding that stuff doesn’t matter anyway,” says Giovannetti. “So why even hide it? It just makes this artificial memory barrier and that’s not a skill I was interested in testing anyway.”

And for new players, a layer of busywork and wondering was removed. Not a single playtester wanted to go back, and as they took the game to local game shows they noticed huge differences between people who played the builds with and without the precise numbers.

The dynamic range of the game, meanwhile, opened up. When players could respond to enemy attacks in meaningful ways, the range of damage they could score on the enemies rose because they didn’t have to conservatively block in case they were hit on the next turn. MegaCrit also noticed that players felt greater freedom to invest in strategically useful cards such as powers, which are energy-expensive but repay their value over the long term, because they could make the choice of either taking a hit or finding a safe time to play it.

“And it’s added a design space that we’ve only just started to scratch the surface of, like Spot Weakness, where it says if the enemy is going to attack it gives a benefit,” says Giovannetti. “We can do other cards like that as well, where effects matter based on what the enemy is doing. It opens up a richer possible play space.”

Revealing everything turned out to give everyone greater room to move, think and play.


  1. Jeremy says:

    It’s so interesting to see the prototypes, and how much can change and remain the same. I’m so glad they landed on making everything clear. Guessing on damage, or even on actions would have made the game a slog (for me.) Being able to plan around numbers, and knowing when to sacrifice health here or there is what makes the game so great for me. Guessing each round would have ruined it.

  2. shagen454 says:

    That’s exactly the reason I’m not a huge fan of it… I like it, it’s fun but it’s just lacking a bit every where to keep me hooked imho, even for a humble indie developer.

  3. Faldrath says:

    StS is fantastic, and Steam says I’ve already sunk 30 hours into it. I do love the intent system, it makes every turn a small puzzle that fits into a larger one. Of course, sometimes RNG will kick you in the teeth, and you learn that to be successful you want (a) a not very large deck, less than 25 cards, ideally less than 20; (b) a lot of defense – it’s very easy to be tempted into buying all the fancy attack cards, but that’s a sure ticket to the graveyard when you inevitably draw that hand with 5 attacks and no defense as the enemy lines up their mega-attack.

    I guess one bad consequence of that is the fact that if you want to be successful at all, you kinda need to have your deck pretty much ready by the second half of Act2. Which makes most of Act3 feel not very rewarding, since you basically just skip almost all the card rewards then – because deck bloat is the main danger, and by Act3 using the merchant to get rid of cards is almost always prohibitively expensive.

    • Hidoshi says:

      I like how your opinion has a lot of assumptions which are definitively not true based on how I’ve played and finished the game.
      A: based on your strategy you can have 40+ cards. For example I had one where I was milling through 15 cards every turn, and did damage every time I discarded or drew a card. Another example was with the “Strike” deck, where your (forgot the name) Strike does damage based on the amount of strike cards in your deck. You just have to balance deck size with milling power
      B: Either have a lot of defence, have enough defence, have turn based defence or have no defence but finish fast

      I fully agree on the part on act 3 not feeling rewarding with cards though.

      • Faldrath says:

        Fair point about my unwarranted generalization, but I still think that card-heavy decks are the exception rather than the rule. If you want a successful “normal” poison, attack, shiv, demon build etc., you’ll generally want fewer cards unless you stumble into the specific cards/relics that enable the strategies you mentioned.

        Regarding defense, I haven’t found a way to make low-defense/defenseless decks work yet. When you get to act 3, monsters start having way too much life and doing way too much damage for you to kill them before they kill you (especially the final boss, of course). Granted, I don’t follow streams, nor reddit, etc., so I’m sure someone might have figured out a way to survive – but I’ll claim, again, that it’s the exception rather than the rule.

  4. Watercat5 says:

    I can’t believe the amount of people who praise this game like it is some sort of genius design. The clarity of information is necessary for a choice of card system that consists of attacks and defends.

    Imagine if the enemies didn’t tell what they were going to do. Blocking would be a waste of time since you can’t know if the enemy is attacking. Therefore, pure offense wins out, and it just becomes a boring race.

    Obviously some sort of predictability must be used. One option is to have predictable enemy patterns, but the developers did not want to use this for the reasons stated. Therefore, the only option is to display the information. Otherwise, the basis of their entire card system would be completely lop-sided in favor of attacks.

    Also, the reason the game has good clarity is because it has simple mechanics. It is easy to convey something like “deal 5 damage”. While this simplicity makes information more accessible, it also limits the game’s upper limit in terms of strategy, and many people will find Slay the Spire boring because of it. Already the first floor is basically a waste of time, and the only interesting part is seeing what cards/relics you will get to use later.

    • HopeHubris says:

      I’ve played a bunch of deckbuilding roguelikes, most of which don’t give you visibility on the enemies next move. It’s clearly not the only way to do it, StS also has a “Can’t see enemy moves” relic, which doesn’t make blocks useless either.
      Sure, you can try to just do a full damage speedy run, but you’re likely to get blocked by half of the enemy types

      • Watercat5 says:

        In the same vein as the other commenter I replied to, the difference is that Slay the Spire does not carry over block. Please show me any of those deckbuilding roguelikes that also don’t carry over blocking and yet don’t show what the enemy is doing. The only way I could imagine that is if the game allowed you to easily heal, which Slay the Spire certainly does not. If you can heal, you can afford taking damage. It will play out much like older final fantasy games where there is only attacking and healing in that case.

        Also, speaking of the relic Runic Dome that you are alluding to. You only take that when you don’t care if the enemy is attacking or not. The extra energy it gives you allows you to either create high value combos that are worth potentially not knowing the information, or it allows you to both defend and attack more effectively. Besides, the enemies basically have patterns anyway, and a good player will know all the possible attacks the enemy can do.

    • MercurialJack says:

      Clearly you have not played any other games like this, or just not very well. This clarity of information is not necessary, it is a deliberate design decision and over and above the standard you’d expect.

      Take Monster Slayers, a nearly identical game for most intents and purposes. Deck building rogue-like, and doesn’t telegraph the enemy’s next move at all. If you only go all out damage without blocking or healing yourself or trying to mitigate in any way, you’re not going to last very long at all. There is no predictability or pattern – you don’t know what cards the enemy has in their hands nor which ones they might play, just what their available AP/MP are. Blocking is necessary and the card system isn’t lop-sided. Try opening your mind just a little beyond your own initial narrow thoughts.

      • Watercat5 says:

        Correct me if I’m wrong, but after looking up info on Monster Slayers, there is one key difference: block is preserved between turns.

        This completely changes the dynamic and is one thing I neglected to mention. In the case of Slay the Spire, block does not persist between turns except in some circumstances. Therefore, if you play block and either overblock or the enemy doesn’t attack, you have wasted your resources. In Monster Slayers this does not appear to be the case.

        If you preserved block between turns, the optimal way would be to only play defends and then buff/attack as necessary to win. In fact, you will see this in Slay the Spire quite vividly when you see the single strongest deck is a barricade deck on the Ironclad that lets you preserve block between turns. A deck with Barricade and Entrench is almost unlosable unless the deck is very bloated.

  5. kadeton says:

    MegaCrit have hit exactly the sweet spot (for me, at least) between “not enough information” and “too much information” with Slay the Spire. There’s still plenty of hidden information – you generally don’t know what cards you’re going to be drawing next, or what the enemies are going to be doing the turn after next, as examples.

    It’s also worth mentioning that playing around with access to information is part of the game. There’s a relic that makes your character more powerful but prevents you from predicting the action the enemies will perform next turn – I will never take this, because it makes the game pretty much impossible for me. There’s also a relic that reveals the order of the cards in your draw pile – that knowledge, combined with a lot of card draw, can give you immense control over the game.

    It’s a really interesting mechanic.

  6. spindaden says:

    Guild of Dungeoneering does this too, it’s a card based dungeon crawler too and you can see the enemy’s next card and also, before you engage them, you can see some attributes that describe the types of cards in their deck. I’ve not played StS, but I think this is a great way of introducing variety in the combat without the player feeling cheated.

  7. Imbecile says:

    I’ve not played it yet, though I plan to, but I instinctively dislike the concept of knowing what your opponent will do next turn.

    One of the key skills of actually playing a card game, as opposed to deck building is the ability to predict what your opponent is likely to pull off. It’s one of the key factors in the better card games like netrunner or shadowfist

    Without that you lose the skill of anticipation, prediction and bluff, and leave what? I’m genuinely curious as to why it seems to work?

    • Cut says:

      Maybe you are confusing the pleasure to be had playing a real human being – where you (calculate), anticipate, predict and bluff your way to victory – with the completely different experience of playing an AI opponent – where nothing except calculation really works.

      You can’t look your PC in the eye, flutter your eyelashes innocently and maintain that “*of course* I don’t have an Agenda in my hand…”. Which is why Netrunner will never be fun to play vs a computer.

      On that last point, Demis Hassabis may yet prove me wrong, of course…

    • ButtonDownMind says:

      You’re trying to look at Slay the Spire like its a CCG, but it isn’t (I don’t like CCGs and really enjoy StS). StS is a deck-building rougelike. You’re not facing off against an AI masquerading as a player, you’re navigating a dungeon and fighting monsters using a deck you build along the way. Each individual monster only has 4-5 moves max (they don’t play cards against you). The variation and importance of prediction aren’t as important at the individual combat level of the game, but are very important when it comes to navigating the game’s map, through which you can control how many/what types of fights you’ll encounter.

      • Imbecile says:

        Ah gotcha, thanks. I think I’m probably comparing apples and oranges. As you both say if it’s not versus a human and if it’s not really a CCG them the same rules don’t apply. I guess I really should check it out, as a fresh perspective is always good (I design for a CCG, and it’s surprisingly easy to get stuck in a rut, offering up reworkings of existing cards)

  8. gaaraati says:

    Slay the Spire is great! It’s one of the best roguelikes I have played. I can’t really decide if StS or TBOI:R is the roguelike of my life lol.
    I have played almost 100 hours in a month. This is a lot considering I’m home only for 6-8 hours on an average day. I really like this game and I’m happy we could see how the game has changed.

    It’s awesome that they were able to pull off such a huge change. It was for the greater good. The game is freaking addictive and it is so fun!

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