posted 10-28-2000 02:46 AM               

“Yomi” is a Japanese word meaning “knowing the mind of the opponent.” It comes from the lingo surrounding Virtua Fighter, perhaps the most complex video game ever made. If you can condition your enemy to act in a certain way, you can then use his own instincts against him (like in Judo). Paramount in the design of competitive games is the guarantee to the player that if he knows what his enemy will do, there is some way to counter it.

What happens, though, when your enemy knows that you know what he will do? He needs a way to counter you. He’s said to be on another level than you, or another “yomi layer.” You knew what he would do (yomi), but he knew that you knew (yomi layer 2). What happens when you know that he knows that you know what he will do (yomi layer 3)? You’ll need a way to counter his counter. And what happens when he knows that you know….

Sound like a joke that could never happen in real gameplay of an actual game? Surprise: it’s quite common in strategy games. The reason has to do with conditioning the opponent and the inequality of risk/reward in these guessing games (see my article on Rock, Paper, and Scissors in Strategy Games).

Before we get into how ordinary human minds can become entangled in complicated guessing games, let’s look at what needs to be there to create these guessing games at all. The designer’s tendency might be to create moves and counters. Then create counters to counters, then counters to counters to counters, then counters to those, and so on. Actually, a game need only support counters up to Yomi Layer 3, since Yomi Layer 4 can loop around back to Yomi Layer 0.

Let’s say I have a move (we’ll call it “m”) that’s really, really good. I want to do it all the time. (Here’s where the inequality of risk/reward comes in. If all my moves are equally good, this whole thing falls apart.) The “level 0” case here is discovering how good that move is and doing it all the time. Then, you will catch on and know that I’m likely to do that move a lot (yomi layer 1), so you’ll need a counter move (we’ll call it “c1”). You’ve stopped me from doing m. You’ve shut me down. I need a way to stop you from doing c1. I need a counter to your counter, or “c2.”

Now you don’t know what to expect from me anymore. I might do m, or I might do c2. Interestingly, I probably want to do m, but I just do c2 to scare you into not doing c1 anymore. Then I can sneak in more m.

You don’t have adequate choices yet. I can alternate between m and c2, but all you have is c1. You need a counter to c2, which we’ll call c3. Now we each have two moves.

Me: m, c2
You: c1, c3.

Now I need a counter to c3. The tendency might be to create a c4 move, but it’s not necessary. The move m can serve as my c4. Basically, if you expect me to do my counter to your counter (rather than my original good move m), then I don’t need a counter that; I can just do go ahead and do the original move…if the game is designed that way. Basically, supporting moves up Yomi Layer 3 is the minimum set of counters needed have a complete set of options, assuming Yomi Layer 4 wraps around back to Layer 0.

This is surely sounding much more confusing than it is, so let’s look at an actual example from Virtua Fighter 3 (which will almost certainly confuse you even more).

Example of Yomi Layer 3 from Virtua Fighter 3
Let’s say Akira knocks down Pai. As Pai gets up, she can either do a rising attack (these attacks have the absolute highest priority in the game) or she can do nothing. A high rising attack will stop any attack that Akira does as she gets up, but if Akira expects this, he can block and retaliate with a guaranteed throw. Pai does the rising kick and Akira predicts this and blocks. Now the guessing game begins.

Akira would like to do his most damaging throw (that’s his m), and be done with it. Even though the throw is guaranteed here, all throws can be escaped for zero damage if the defender expects the throw and enters the throw reverse command. The throw is guaranteed to “start” but Pai might reverse it. In fact, Pai is well aware that a throw is guaranteed here (it’s common knowledge), and it’s only obvious that Akria will do his most damaging throw. After all, this situation has happened a hundred times before against a hundred Akiras and they all do the same thing. It’s really conditioning, not strategy, that tells Pai she needs to do a throw escape here (that’s her c1). In fact, it will become her natural, unthinking reaction after a while.

Akira is tired of having his throw escaped again and again. He decides to be tricky by doing one of his very slow, powerful moves such as a double palm, a reverse body check, a two fisted strike, or a shoulder ram (we’ll just lump all those into c2). Why does a big, slow move work in this situation? First of all, if Pai does her throw escape and there is no throw to escape, the escape becomes a throw attempt. If her opponent is out of range or otherwise unthrowable for some reason, her throw attempt becomes a throw whiff. She grabs the air and is vulnerable for a moment. One important rule in VF is that you cannot throw an opponent during the startup phase or the hitting phase of a move. So if Akira does a big, powerful move, he is totally unthrowable until after the hitting phase of the move is over and he enters recovery (retracting his arm or leg).

Back to our story. Akira is tired of getting his throw escaped all day, so he does standard counter to any throw: a big, powerful move. This c2 move does a decent amount of damage, by the way. The next time this whole situation arises, Pai doesn’t know what to do. Her instincts tell her to reverse the throw, but if she does, she is vulverable to Akira’s slow, powerful move. Rather than go for the standard reverse, Pai does her c3 move: she simply blocks. By blocking, she’ll take no damage from the Akira’s powerful move, and depending on exactly which move it was, she’ll probably be able to retaliate.

So what does Akira do if he expects this? In fact, he needs no c4 move since his original throw (m) is the natural counter to a blocking opponent. A throw is a special kind of move that grabs an enemy and does damage regardless of whether they are blocking. It’s specifically designed to be used against an opponent in block who is afraid of an attack.

In summary,

Akira has: throw; powerful, slow move
Pai has: throw escape; block.

As I tried to show, it’s actually pretty reasonable to expect players to be thinking on Yomi Layer 3, 4 or even higher. It’s because conditioning makes doing the throw escape (c2) an unthinking, natural reaction. But against a clever opponent, you’ll have to think twice about doing a standard throw escape, or blocking. The Akira player will do the occasional powerful, slow move just to put his enemy off balance and abandon his instinct to escape the throw. Then Akira can go back to his original goal: land the throw.

Another very interesting property is “beginner’s luck.” Notice that a beginner Akira in this situation will go for the throw, since that works on other beginners who haven’t learned to throw escape. The beginner Akira will never land the throw on an intermediate player, though, since the intermediate player knows to always throw escape. But strangely, the beginner will sometimes land the throw on the expert, since the expert is aware of the whole guessing game and might block rather than throw escape. Of course, the expert will soon learn that beginner is, in fact, a beginner and then he’ll be able to yomi almost every move.

Just as a final note on Virtua Fighter to further demonstrate the complexity of its guessing games, I actually greatly simplified the example above. I left out, for example, that Akira has another c2 move besides a slow, powerful move. He can also do what’s called a “kick-guard cancel” or “kg.” This means he can press kick, which will make him unthrowable until his kick reaches recovery phase. If Pai tries to throw, she’ll whiff. But then Akira can cancel the kick before it even gets to the hitting phase. Now he’s free to act and take advantage of Pai’s whiffed throw vulnerability. Now, Akira has a guaranteed throw, putting him back in the exact same situation he began in. The catch is that if Akira does kg-cancel and then goes for the throw he originally wanted to do, Pai will probably not have time to react with a throw escape. It’s just too fast. She’d have to be on the next yomi layer. She’d have to expect Akira to throw, enter a throw escape, see the kg-cancel, then immediately enter her next guess (probably an attack or throw escape). Any hesitation and she’d be thrown.

Crazy huh?

The point I’m making here is that despite Virtua Fighter’s absurd complexity, players really are able to think on the levels I’m hinting at. Playing such a game and successfully landing a move because you knew he knew you knew he would do a particular move is the greatest feeling in the world. So design counters and counters-to-counters, and so on, but know that making Yomi Layer 4 the same as Layer 0 allows you to only design counters up to Yomi Layer 3. It’s nerdy, but true.

posted 11-08-2000 07:10 PM               

I'm not familiar with that. Post about it or e-mail me if you like. =)

posted 12-06-2001 01:24 PM            

Aoi has her high rising attack blocked by Kage, who has the deadliest throw in the game. Aoi mashes on a b+P+G escape because she's expected this throw (the ten foot toss). Kage knows that aoi is going to do this and comes up with a plan. The next time he does f+P+G, which places him behind an opponent. The standard guaranteed followup here is a dragon punch. However, Aoi is the only person who can reverse moves with her back turned. Because she sees Kage dragon punch after f+P+G all the time, she does her back-turned reversal. It turns out that Kage has played a few Aoi's and knows that his dragon punch will always get stuffed here. So Kage crouch dashes forward and does a damaging catch throw while aoi's reversal whiffs. This isn't really 4 or 5 layer yomi, it's more like a couple of 2 layer yomi's that happen successively.

Another example that I love which I've seen on a video: Wolf is facing Akira on Jacky's VF3. Wolf has a guaranteed throw here, and since his back is to the edge of the ring, he wants to a do a twirl'n'hurl, a move which throws the opponent directly behind him. Akira knows this and does a twirl escape (b,f+P+G). Wolf doesn't twirl, instead he waits a second then enters f+P+G. What happens is this. Wolf's hesitation causes Akira to throw him. Specifically Akira does the b,f+P+G throw, one which sends the opponent flying away from him with a shoulder ram. But Wolf knows it's coming and instead enters f+P+G. Wolf escapes Akira's throw, and one of the peculiar things about escaping that throw is that Akira ends up sprinting past you 15 feet. It's like he has to do something with all that built-up momentum that was going to be a throw. So Akira sprints past Wolf and directly out of the ring. Even without seeing the Yomi layers someone can observe that Akira just got schooled.

One last thing. I know I have a tendency to write forever.

You should do an article on the concept of "insurance" in a game. In SF, insurance might take the forms of pokes (and I'm sure you have other examples). In VF it comes from double throw escapes and reversals, some of which are all glued together. Like in the classic "high rising attack was just blocked" example, the riser can quickly enter b+P+K, P+G, b+P+G in succession, and that insures him against high attack retaliations (b+P+K reverses high attacks), neutral P+G throws, and throws that end in b+P+G. You have a sense that the opponent will throw you with b+P+G, but the reversal and P+G throw escape are there in case he switches up on you or fails to do the throw properly.

In some quake tournament videos I've been watching, both players throw a -lot- of seemingly random rockets into the entrances and exits of every room they walk into. These insurance rockets do nothing 9/10 times, but the other 1/10 times they luck out and catch someone just as they're walking into the same room. Where yomi comes into play is when the better player hears the teleport sound effect, knows that the opponent just teleported, and predicts the route that he'll take from there (because usually there's only one or two routes leading away from that point anyway). I've seen the winning player listen to a teleport, run to a specific doorway, sit and wait maybe 4 or 5 seconds from that doorway, then fire off a rocket. The timing is perfect and the opponent runs into the rocket just as he rounds the corner.

posted 04-09-2002 11:16 AM            

The idea is that you can guess what your opponent will try and do, and then counter that move. e.g. if your opponent prefers a certain route through the level, you can figure out the best ambush points.

posted 07-30-2002 06:07 PM               

I was a top player in college, and in reading your articles, I found myself drawing parallels to my gameplay style. The top player vs scrub and Yomi level X especially. Let me explain...

As you know, before a hand of hearts is played, you pass 3 cards from your hand to another player, and receive 3 cards from someone else. It adds some uncertainty to your plan for play. A long standing scrub-style rule is to always pass a low heart, making it very difficult for the recipient to "shoot the moon." Once this "rule" is established, one can go Yomi on them and know that a heart is coming to you. Then, the next logical conclusion is that you should pass all 1 low heart and 2 high cards, and forego any intentions of shooting. Go Yomi one more level, and know that your passee is expecting a low heart, and is passing away his high cards. So that's when you pass him 3 aces, and listen to him groan at the shoot he could've had if he'd known that pass was coming.

Of course, you must mix it up, and my general strategy was to pass all high cards only when I had a very bad hand, and I needed every bit of help I could get.

It also helps to know which players like to lead low spades to "smoke out the queen", or try to avoid getting the lead at all costs (they usually end up with high cards at the end of the hand).

Counting cards is a must, if you sense that a shoot is on, then the 3 non-shooters form a quick alliance to stop the shooter. Even if that means "taking one for the team", you build a reputation as being trustworthy. All the better to lure them into the false sense of security.

Well, this was not very well written, but I hope I tied in the concepts of Yomi, RPS, and Alliances in somewhat understandable ways.

posted 08-10-2002 11:08 PM               

"There are those who are content to lean on chance, and play whist, and there are those who must reamin in control, and play chess."

Ah, almost forgot. The practice of shooting around every corner in FPS's is called "ass-fragging." I like to think of it not so much as cheese, as most people seem to, but rather as simply being an incredibly homicidal "fisher of men."

------------------
Murder is on the menu.

posted 08-11-2002 12:47 AM            

You think hearts is complex? Try bridge.

posted 08-11-2002 09:41 PM               

The general issue, however, is what's got me grinning in a 'Well, mayyyybe' sort of way. As you say, what's the difference between reading a man's mind and playing percentages, which is basically reading the universal mind? I suppose I'd say that you're dealing with yomi when you have access to personal determinants that by their nature give you an edge even over flawless number-crunching. Here's me going out on a limb, right, heh...but that's as far as it seems to want to be taken. Weirdly, yomi seems to be both inductive and deductive in that most of the time you're basing it on what you've evidenced in his play, but the whole assumption is ruined if your guess isn't based on true premises (ie, I must both know that he likes to throw and that he WILL throw). So, we all know that yomi is a damn weird power, but keep resorting to it because it's a practical power.

Where I start sounding crazy in these sorts of topics (or at least reeeally liberally speculative) is when I point out that I believe knowledge (still yomi, tho?) can be stretched to the point where the open book isn't only the player's head, but the situation in general--this amounts to a Zen state where the 'design' of things becomes known and you unconsciously adapt yourself to the 'right' play/Way/action. It sounds like crystal-ball stuff on paper, but I would be very surprised if gamers out there, and as a good test, Sirlin himself, have not experienced this state at least once. 'Should happen' becomes 'will happen' in this Peak Yomi, which spits right in the face of logic and the probability theory that uses should/will alchemy to the same ends, but in a method vulnerable to screwing it all up ('best' play's rarity making us look dumb again). The tie-in I happened upon was the Zen saying of "the normal mind is the Way." So this state, if it does exist, is 'more normal' to the pt that you can plug yourself into the harmony of people AND events. Of course, I've never been able to sustain it in the few times I can make a case for its appearance. It enables the miracle and goes elsewhere. As I say, SOUNDS crazy, and the only way I'd go about 'proving' it is to pull a Maslow and just watch and interview.

Pretty on-topic for the first 2/3 of it...bit of a record for me, tho I admit I prolly stopped talking about yomi proper at the end. Guess all that means 'that's a good question'.

posted 08-15-2002 07:41 AM            

Many FPS games can be highly strategic. There is the obvious case of Capture the Flag (a strategy game in its own right) and the extreme case of Team Fortress games (specialized strategic combat). Even DM can be strategic though - its simply the case of Q3 that the game is highly reflex based with simple equipment and weaponry.

The weapons in Q3 are extremely simple - theorecally, if two "gods" are fighting with machineguns then their movements are irrelevent to combat - if you can see your opponent, you can kill them. The railgun reactions are totally random - since you are perfectly manoeverable in Q3, then you cannot really lead the target unless he is stupid enough to run in a straight line or is airborne. Avoiding the railgun is similarly random - the rail beam appears where the firer was standing/facing 1/4 ago - so unless you know exactly where he was facing, you cannot dodge it - you can only move randomly. The other weapons are all very simple, no tricks, no other options for strategy other than "point at the enemy and open up". Q3 has one good gameplay concept thought - the only actual full "hitscan" weapon is the machinegun. Every other weapon is theoretically avoidable. The lightning gun rotates slower then the player. Rockets, grenades and plasma bolts can be dodged. The railgun has a delay before the beam appears. The shotgun has a limited effective range due to its randomspread.

High level combat in Q3 is almost always the result of good level design more then the game itself. A good level will force the player to make complex decisions on which "path" of the level to run for equipment/position, based on the current known and unknown positions, skills and equipment of the players in the game.

UT is an example of a much more intricate game. First, UT slows combat down, allowing players to develop strategy on the fly, rather then running on learned reflexes (hence why it is often maligned as "Quake for girls/kids"). Also, the UT weapons are much more strategic. The 8ball is an excellent example - you can use the grenades to "spam" often travelled corridors, you can single-fire rockets in combat, or if you expect to fight in the next 5 seconds you can preload up to 5 rockets (you will lose them automatically when they reach full capacity). The Biorifle is a simple mine-layer. The shock-rifle combo attack can be used to generate a powerful explosion on a point in space, not necessarily on a wall like most explosive weapons. Slower moving projectiles often result in much more strategic but spammy play, as anticipation and analysis of likely player locations at X seconds away becomes very important, and dodging becomes more then just simple random movement to throw off the enemy's aim.

UT also has a built-in personal teleportation device called the X-Loc for teamplay. If you can hit a point on the map with your beacon, you can teleport there. This means that getting to high towers with full view of the map becomes very handy for moving, not just defending - you can use it to escape tight situations, or use it to get right back into the action after going to pick up out-of-the-way equipment.

This allows for much more complex strategy and counter-attacks, even in DM play. Each weapon has a wide variety of possible approaches to combat, each witht their own defenses.

That being said, UT has Yomi-idiotic weaponry too. The entire strategy with the sniper rifle is "point at enemy's head, fire". There is no dodging (it is instant hitscan), there is no defense but moving erratically and hoping the enemy misses. This is why I don't play "realism" games - their weaponry is undefendable. Their strategy is team-play only (proper movement/grouping and deployment) but their combat strategy is incredibly simple - try and keep a minimum amount of space around you that people could be shooting from, but try can keep a good, hard to detect avenue in front of you to shoot at. This is highly conducive to teamplay (needing people to watch your back/sides) but also makes for rather boring individual combat (hunt hunt hunt hunt hunt hunt hunt hunt hunt hunt hunt bang done).

Shogo is an interesting example of a gameplay feature that removes item whoring from FPS games - in Shogo, you can transform into a high-speed non-combat vehicle and run around. This means that you should never be behind in equipment, as you can transform to run away or to go hunt for gear. You have no excuse for some guy makeing him your bitch 'cause you've got no gear.