This FAQ is by "The V", 01-06-03, Version 1.0. Copyright 2001. No part of
this document may be reproduced and distributed via means mechanical or
otherwise FOR PROFIT (this includes distribution in ANY publication that
is sold) without the consent of the author. Reproduction and distribution
for any other reason (e.g., personal use, discussion) is welcome so long
as the author is given appropriate credit. 

All games, characters, names, etc. are trademark and property of their
respective company, Capcom.

The ideas presented in this FAQ is based on the personal experience,
observations, opinions, and readings of a SFIII: Third Strike player who
has played the original SFIII and SFIII: Second Impact.  

Comments can be sent to viwong@interchange.ubc.ca


=====================================================================
                   Street Fighter III: Third Strike
                   Parrying Strategies Analysis FAQ
=====================================================================
CONTENTS:

1. Introduction
2. Parrying Types
   2.1 Damage Prevention Parrying 
   2.2 Offense Creation Parrying
3. Theoretical Optimal Strategies
   3.1 Air-to-ground Analysis
   3.2 Air-to-air Analysis
4. Deviations from Theory
   4.1 Individual Player Differences
   4.2 Character Differences
   4.3 Throws
5. Conclusion
_________________________________________________________________________
----------------
I. INTRODUCTION:
----------------
Parrying is the trademark game play mechanic of the entire SF III series
that was simplified slightly in SFIII: Third Strike. Parrying is a simple
addition; by directing the lever forward or down at an appropriate
incoming attack at the appropriate time a player is rewarded by taking no
damage from the attack at all. Perhaps it is because of its simplicity
that it is embraced by some players and despised by others. Nonetheless,
despite ones feelings toward the system, its advent does provide a new
level of strategy to the game. It is the purpose of this FAQ to discuss
some of the complexities behind parrying and its consequences on the
players and the game. The material covered is primarily with reference to
the parrying system found in Third Strike, but many of the ideas are
applicable for the other two SF III titles as well. We'll begin with an
overview on the different types of parrying people employ, namely damage
prevention and offense creation. The discussion will then move to the
theoretical optimal strategy in specific combat situations for both the
defender and the aggressor. Finally, the limitations of the theoretical
optimal strategies in real game situations will be addressed.
________________________________________________________________________
-------------------
II. PARRYING TYPES:
-------------------
When one observes players utilising parries, two distinct categories
emerge. One class often involves reducing damage and the other for
creating an opening. I
2.1 DAMAGE PREVENTION PARRYING

A damage prevention parry (DPP) is simply when a player parries to avoid
taking unnecessary damage. For example, say a Ryu player uses a Hadouken
from the opposite side of the screen and the defending Hugo player parries
it. It is clear that the Hugo player
2.2 OFFENSE CREATION PARRYING 

In contrast, for the offense creation parry (OCP), a counter attack is not
only an available option but is the objective of decision to parry
(serendipitous parries where a player suddenly finds him or herself in a
retaliatory position are not true offense creation parries, but have the
same effect of one). For example, say an Ibuki player, with the intention
of parrying, is jumping in on a Dudley player who always retaliates with a
standing hard punch. Notice that the Ibuki
player__________________________________________________________________________
------------------------------------
III. THEORETICAL OPTIMAL STRATEGIES:
------------------------------------
As hinted previously offense creation parries (OCPs) can be utilised by
both the defender and the aggressor. The question now is when should the
tactic be employed as to gain a maximum payoff? That is when is an OCP an
optimal strategy? As in most interesting games, the answer depends on the
response of the opponent. Let us look at a common situation in the SFIII,
an air to ground attack (i.e., a jump in). We will focus on the attacking
(i.e., the jumping) player. What options does the attacker have? In SFIII,
there are no air blocks which leaves the attacker with a choice between a
strike or a parry. The defending player, however, has three
options: strike, block, or parry. Let us say for simplicity that if left
unscathed each of the aggressor and defender have a value, V. If either
party is successful in dealing damage, they are rewarded with a bonus
value B. Also, since the aggressor has fewer options than the defender
(can
3.2 AIR-TO-GROUND ANALYSIS

Let us begin with a situation where both the attacker and defender strike
and we will assume that the attacker will make a successful strike half of
the time and an unsuccessful one the other half of the time. In other
words, the attacker will have his V increased by B half the time (+
B/2) and decreased half the time by the same value (- B/2). In addition,
the aggressor always accrues the C value so the payoff for the attacker
when he or she decides to strike and the defender also decides to strike
is: V + B/2 - B/2 - C. If the attacker strikes and the defender blocks and
we assume that the attacker always deals block damage (e.g., with a combo
that ends with a special or super move), then the attacker will have his
or her V increased by whatever fraction of B that gets through as block
damage minus the cost for striking. I
                                   Defender

                  ____Strike____________Block________OCP_______
                                   |             |
          Strike V + B/2 - B/2 - C |V + 1/5B - C | V - B                          
                 __________________|_____________|_____________
Attacker                           |             |
          OCP         V + B        |      V      |   V   
                                   |             |
 
Chart 1: Payoff Matrix for an Air-to-Ground Encounter.          

We can see then that the best strategy to use depends on what the defender
is doing (recall that we are focusing on the aggressor). If the defender
always strikes, then an OCP is the obvious choice, for
instance. Conversely, if the defender always blocks then striking is the
best move. What if the defender randomly performs one of the options
available? Still an OCP is the best option as there is no instance where
the aggressor would lose a B amount, but the defender will 1/3 of the time
and the other 2/3s of the time both players break even. If we switch our
attention to the defender, an OCP will be the best option if the aggressor
always strikes and blocking or parrying with either type, OCP or DPP
(though, from here on in, for simplicity I'll ignore DPPs because I'm
going to assume that the sprites are always in a postion where a
successful OCP will always lead to an opening so there is little reason to
use a DPP, but be aware that it is an option) would be best if the
aggressor always uses OCPs. If the aggressor uses strikes and OCPs at
random, then the best option for the defender is to always use an OCP as
he or she will get the + B amount half the time and break even the rest of
the time. In short, the best strategy for both parties, when in doubt, is
to always use a OCP because at worst each will break even (i.e., both
retain their V amount). It may seem that the defender could use a
substitute strategy of "always block" for "always parry" and also break
even, but this option is not stable because if confronted with an attacker
that does not adhere to an "always parry" approach, the defender will give
up B amounts; whereas, if the defender persistently uses OCPs a deviant
strategy on the part of the aggressor will result in a loss of B for the
aggressor. (Why strong players in real life do parry a lot in these
situations but not always will be addressed later). 

3.2 AIR-TO-AIR ANALYSIS

Similar analysis can be done in different situations such as air-to-air
and ground-to-ground. (I will discuss air-to-air only because
ground-to-ground interactions are very complicated as we would have to
take into consideration low and high blocks, low and high attacks, and low
and high parries). However, we will have to modify the options for the
defender and aggressor in these situations. For example, in air-to-air
confrontations both parties have no block option and there should be no
"defensive move" advantage, so we would have to remove the C value for the
aggressor and take away the block option for the defender. (However, in
ground-to-ground situations both parties will have a block option and we'd
also assume no C because there doesn
In an air-to-air confrontation then, each player has two options: strike
or parry. If both strike, then using the same symbols as before, each
should get a payoff of V + B/2 - B/2  (which, of course, is just
V) because, as before, we'll assume a successful strike half the time. If
one player uses a strike and the other uses an OCP, then the striking
player will lose the B amount and the parrying player gains the B
amount; in symbols it is V - B and V + B, respectively. Finally, if both
players use an OCP (recall we're ignoring DPPs for now), then both players
retain their V amounts. The following chart (the focus is on player 1) is
a summary.  


                                 Player 2

                  ____Strike____________OCP_________
                                   |             |
          Strike  V + B/2 - B/2    |   V - B     |                        
                 __________________|_____________|__
Player 1                           |             |
          OCP         V + B        |      V      |     
                                   |             |

Chart 2: Payoff Matrix for an Air-to-Air Encounter.

Parrying is the best move for either players in all situations (only if
our assumption of 50% strike success is true, which in real life it
isn't; why that is the case will be dealt with later). For example, if
someone always strikes, then the opponent should use an OCP (one could
also always strike back to break even; more on this option in the next
section). If someone always uses an OCP, then the opponent should always
use an OCP as well because that way each player will break even. If a
player randomly uses strikes and parries, then the opposition should
always use an OCP because half the time the parrying player will get a + B
while breaking even the rest of the time. In summary, parrying appears to
be the best option in air-to-air confrontations, but only under very
stringent assumptions (e.g., 100% parrying success). 
________________________________________________________________________
---------------------------
IV. DEVIATIONS FROM THEORY:
---------------------------
We'll see in this section that when we consider individual player and
character differences plus when we factor in throws we can account for why
players don't always parry even though it may seem like the best option
available in theory.

4.1 INDIVIDUAL PLAYER DIFFERENCES

In order to simplify analysis many assumptions were made that do not
necessarily hold true in a real gaming situation. Firstly, there was the
assumption that when a player decides to parry he or she has a 100%
success rate. Second, if a strike is parried, then the striker is always
in a position where the parrying player can take full advantage. Third, we
assumed that all strikes can be parried. Lastly, we assumed that all
characters are equal. (We'll deal with assumptions two through four in the
character differences section.) Parrying is a skill that takes much
practice to perfect. Even the best parrying players can miss a parry due
to lack of concentration, error, mood, and a variety of other reasons. In
addition, there is natural variability in parrying skill between
players. This means that in choosing whether to utilise an offense
creation or damage prevention parry or to consider other options the
player has to factor in his or her own probability (less than 100%
probability, of course) of making a successful parry. Recall in the
air-to-air situation where one player (we'll call Tim) confronts another
player (we'll call Sue) who always strikes. According to the analysis
parrying is the optimal choice, but what if Tim can only successfully
parry a hit 5% of the time? Then for Tim's skill level parrying is not the
optimal choice and he would benefit more by always striking against Sue
because at least he'll break even (theoretically) with her instead of
losing B amounts to her. I hinted in an earlier section that strike
success is not 50% in real game situations. The reason is because a
successful strike depends on various factors such as character difference,
speed of move, priority, whether the move can be parried and position. If
Tim has better priority say, he might win, for example, air-to-air battles
60% of the time which is better than successfully parrying Sue's attack 5%
of the time. In short, individual skill and otherwise likelihood of making
a successful parry will affect the choice to parry. If parrying for the
individual has a low success rate, then the alternatives available to an
individual player are better than the theoretical optimal choice.  

4.2 CHARACTER DIFFERENCES

Character differences affects whether strikes can be successfully parried
and thus affect player choices in deciding to parry. Stripping away the
cosmetics, a character in any fighting game is really simply a set of
moves. (More precisely, they are a set animations or properties
interpreted by the human player as moves with specific functions. In
contrast, the AI, for instance, has no idea that it is using moves with
functions as it simply follows a few conditional statements a preset
routine, which is one factor why the AI is so predictable and sub-optimal
in its play). The shape of the character (the sprite) gives players a
reference for their determinations of the range of a move and a reference
of when to defend and attack and what to defend and what to attack. Not
all move sets are created equal because some sets have higher priority,
different properties, and range. (interestingly, the sprite often
determines how players react to using a character at first glance; that
is, for example, they expect a large sprite like Hugo to be slow and a
small one like Ibuki to be fast, but there is nothing from a programming
perspective that forbids Hugo to be fast). It is these differences that
make up the uniqueness of each character. These individual differences
affect a player's play and decision to parry as many fighting game FAQ
writers already know (often character FAQs have a "VS specific
character" section). A character might, for instance, contain a move that
when parried may not produce the desired opening because the move does not
set the sprite in the appropriate position (e.g., parrying the very tip of
Remy's standing middle punch during a jump in). Perhaps, in such a case a
player would rather of traded hits then to have unintentionally performed
a damage prevention parry. Some move sets will have examples that can't be
parried at all (though, as far as I know there are only 2 non-throw moves
that can't be parried: Gill's Sephraic Wing and Gouki/Akuma's Kongou
Kokuretsu Zan) or are very difficult to parry, which obviously will affect
a player's decision to parry when playing against such move set
(character). Player's can use moves (the character) to throw off a
parrying player's timing. For example, while performing a chain link combo
with a specific character (only some characters can chain) the player
could stop chaining early and hope to throw off a parrying attempt. Some
character's have moves that can be used to fool a player into performing a
damage prevention parry and then attack with a move that must be parried
with different timing. An example would be Urien performing and EX
Metallic Sphere followed by EX Chariot Attack. Similarly, Ibuki's Kunai
followed by her Yami Shigure, a move that must be parried or blocked low,
is yet another trick. Notice that these tricks and tactics are character
(or move set) specific. When a parrying player is confronted with one of
these characters (or move set) and a player who can perform these tactics
(another example of player differences) then his or her playing strategy
would change because the theoretical strategies are not optimal in these
situations. 

Clearly then, given these examples, our assumptions in the previous
section that a successful offense creation parry always makes an
opening; that all moves can be parried; and all characters are equal are
not always true and in the situations where the assumptions are violated,
players will call upon different tactics.

4.3 THROWS

In order to capitalize on an opening created by an offense creation parry,
each sprite must be in close vicinity to each other - which also happens
to be the vicinity of throws. Throws are the answer to an "always
parry" strategy. Throws can't be parried and will deal damage and shift
the momentum of the match. If a player, decides on an "always
parry" approach he or she must be wary of throws and prepare to counter
("tech", in SF jargon) the opposition's throw attempt. Individual
character differences come into play again as some characters have greater
throw range, throw speed, and throw priority (e.g., special throws like
Alex's Power Bomb) than others. Consider for instance, a Hugo player with
a fully charged Gigas Breaker. This player will likely deter the
opposition's decision to jump in with an OCP. Likewise in an air-to-air
battle against say, Chun Li, who has an aerial throw, a player would have
to decide whether parrying is a good idea. Clever players can attempt to
force a damage prevention parry and dash and throw the opponent as they
are parrying. For example, Sean throws his basketball and the opponent
parries it. Sean could dash in and try a throw. The point is the very
existence of the gameplay mechanic of throws can make parrying a
sub-optimal choice in some situations. However, throws can't be utilised
always as the parrying players could deliberately jump in parrying but
just out of range of a throw and take advantage of the "missed
throw" animation or be prepared to "tech" the throw. 
_________________________________________________________________________
--------------
V. CONCLUSION:
--------------
It was this author's goal to provide a detailed analysis on parrying and
why it can be such an effective tool in the game. In addition, I wanted to
suggest, especially in the last few sections, that the game goes beyond
than just who can parry best (a common target for many critics of this
game). Each player has to consider his or her own skill level, the
specific characters in use, and be ready to utilise all resources in the
game. In addition, the player has to consider the opposing player's
tactics and strategies carefully and hopefully detect a pattern and use an
appropriate strategy against it. Although the ideas presented were not
meant to improve a person's play, I hope that the information at least
paints a clearer picture on why people play the way they do and if that
understanding helps players - well, all the better. How successful I was
with this FAQ will depend on the feedback I get from readers. Finally, as
it is this author's personal belief that Capcom's Street Fighter franchise
is coming to a close - I'd like take this time to tip my hat to a
wonderful series.

