Challenge Design

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Challenge Design
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Challenge Design

• After a protagonist is created and given a goal,
  you will not have a game until obstacles are put
  in the way.
• These obstacles create the challenge faced by
  the player in playing the game.
• Obstacles were briefly discussed in level design,
  as they must be considered when creating and
  properly stocking a level.
• Two types of obstacles, roadblocks and traps,
  tend to be aspects of the levels themselves, and
  do not require further discussion.
• Enemies and puzzles, on the other hand, do need
  a closer examination

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Enemy Design

• As discussed earlier, enemies are opponents that
  have to be defeated through combat, avoided, or
  otherwise overcome to proceed forward in the
  game.
• Enemies are controlled through some kind of
  artificial intelligence, except in multiplayer
  games, in which case some or all enemies are
  controlled by other players.
• Since we discussed the character aspects of
  enemies in our earlier discussion of
  storytelling, we will focus on gameplay elements
  here.

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Enemy Design Artificial Intelligence

• Artificial intelligence can mean a variety of
  different things in different contexts.
• By purist definitions, a game would possess
  artificial intelligence if a game player cannot
  distinguish between characters controlled by a
  human, or by the game itself.
• In such a case, the game would be passing a
  limited version of what is called the Turing
  test.
• In actual practice, however, a game that does not
  pass this test still has artificial intelligence.

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Enemy Design Artificial Intelligence
Screen shot from Unreal Tournament 3. If you
cannot tell if an enemy or teammate is a human
or a bot, then the bots artificialintelligence
has passed the Turing test.
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Enemy Design Artificial Intelligence

• Game developers rarely use the Turing test
  definition of artificial intelligence.
• In a game, artificial intelligence refers to the
  code used to control all non player characters
  and opponents within a game.
• The reactions of the game may be totally random,
  or totally logical, but the control code is still
  referred to as the artificial intelligence of the
  game.
• As long as the right player experience is
  created, that is what counts in a game.
• Recall that this means entertaining the player!

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Enemy Design Artificial Intelligence
Even though the opponent control for Centipede
(left) and block droppercode for Tetris (right)
is simple and scripted, with a random
number generator producing some variation, both
are still considered to be the artificial
intelligence for those games.
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Enemy Design Artificial Intelligence
Screen shot from CompuChess. Without strong
artificial intelligence, a game of chess might
not be worth playing, except for beginners. More
is needed here than in Centipede or Tetris!
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Enemy DesignChallenge the Player

• Providing a reasonable challenge for the player
  must be the primary goal for the enemies in any
  game.
• However, it is generally not advisable to pin
  all your hopes on creating an enemy that can
  compete with human players relying solely on its
  synthetic intellect alone.

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Enemy DesignChallenge the Player

• Aside from a very sophisticated artificial
  intelligence, there are several ways to provide
  challenge to the player with enemies
• Outnumbering the player.
• Giving enemies abilities, advantages, resources,
  or knowledge that the player does not have.
• Assigning the players teammates or additional
  obligations that might hold them back.
• Cheating. (As long as you dont get caught!)
• Poor game design. (Do not do this!!!)

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Enemy DesignChallenge the Player
Screen shot from Doom II. It created challenges
for players by vastlyoutnumbering the player,
and providing opponents many advantages
(unlimited ammunition, seeing in the dark,
flying, and so on).
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Enemy DesignChallenge the Player
Screen shot from Warcraft III. Sometimes, the
difficulty in selecting and controlling units in
the heat of battle provides an unwanted and
frustrating challenge.
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Enemy DesignChallenge the Player

• Creating a challenging and sophisticated
  artificial intelligence can be quite difficult.
• In some games, outnumbering the player and
  providing additional abilities is not what the
  player wants or expects.
• In such cases, the artificial intelligence must
  be very good.
• Depending on the game genre and game
  characteristics, the player must be challenged in
  different ways.

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Enemy DesignChallenge the Player
Screen shot from NHL 2008. It would break player
expectations by giving opponents extra abilities
or by outnumbering the player. The
artificial intelligence must be better to
compensate for this.
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Enemy DesignChallenge the Player
Screen shot from Alpha Centauri. Since it is a
strategy game, the player expects a strong
opponent as the game is very thought intensive.
Since thegame is turn based, the game cannot
overwhelm the player by processing alone the
player can take their time and think.
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Enemy DesignChallenge the Player

• Remember that you are only to challenge the
  player up to a point.
• Keep in mind that your role is not to defeat the
  player, but rather to provide the player a good
  overall experience.
• This means that, ultimately, your enemies should
  put up a good fight to challenge the player, but
  then be overcome so that the player can win the
  game in the end.

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Enemy DesignBe Realistic

• Enemies in a game should possess artificial
  intelligence that is appropriate to their
  setting, story, and own character.
• Characters that are supposed to be smart should
  not do dumb things (usually).
• Characters that are supposed to be dumb should
  not do smart things (usually).
• The more human and realistic a character is, the
  smarter it should behave.
• Beast-like, alien, robotic, and undead characters
  can get away with more stupid actions, depending
  on the situation.

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Enemy DesignBe Realistic
Screen shot from Quake. The Zombies behave
pretty much as one would expect they lumber
towards you and take your shots until they get
close enough for an attack. Unless they are
blown to bits, they willget up and come back for
more, just like real zombies!
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Enemy DesignBe Realistic

• There are some things, however, that are so dumb
  that nothing should do it.
• For example, walking off of a cliff or not being
  able to navigate around a small obstacle.
• In these situations it is obvious to the player
  what the enemy should have done.
• Unfortunately, players seldom recognize how
  complex or difficult such obvious actions are to
  recognize and perform.
• To avoid ridicule, the enemies in a game must
  have a mastery of what is obvious to human
  players.

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Enemy DesignBe Realistic
Screen shot from Quake. The ogre was notorious
for getting stuck in doorways in many levels
with its chainsaw, and not knowing how to get
unstuck.To players, this seemed ridiculous, even
for an ogre.
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Enemy DesignBe Realistic
Screen shot from Oni. In this situation, Konoko
is being chased by Muro. A TCF officer on
Konokos side has beaten his enemy in the
background,and stands over her body for several
minutes. Why isnt he helping me?
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Enemy DesignBe Realistic
Screen shot from New World Order. Unlike most
games, the AI enemies in thisgame do not have
the benefit of infinite ammunition (for realism,
I guess). When they run out, theyll just follow
you around (for no apparent reason),until you
tire of their company and end their misery. Who
thought that up?
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Enemy DesignBe Realistic
Screen shot from Counter-Strike. In the Xbox
version, there is a singleplayer mode with AI
bots for team mates and enemies. When these
eliteterrorists and counter-terrorists fail to
navigate even the simplest ofobstacles, it
totally breaks immersion in the game.
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Enemy DesignBe Realistic

• One must be careful, however, to not make enemies
  behave too realistically.
• Games are often unreal situations set up because
  they are interesting, fun, and ultimately
  entertaining.
• For example, if an opponent realizes it has no
  chance of winning, it should run away
  indefinitely, which quickly ceases to be fun.
• In building good artificial intelligence, one
  must keep in mind the true goal of the project
  building a fun, playable game.

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Enemy DesignBe Realistic
Screen shot from Metaltech Battledrome. A
fairly decent game in its day withincredibly
annoying enemy AI. When the AI had no chance of
winning, it wouldrun away indefinitely. Chasing
down a weaponless mech for an hour to finishit
off is absolutely, positively, not fun! (I speak
from experience )
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Enemy DesignBe Realistic
Screen shot from 007 Nightfire. Realistically,
the villain should just killJames Bond and be
done with it, instead of toying around with
him. That wouldnt make for a very good game
though!
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Enemy DesignBe Unpredictable

• Humans are unpredictable. This is part of what
  makes them good opponents.
• The same should be true of the artificial
  intelligence enemies in a game.
• Players want their enemies to surprise them and
  use strategies and techniques that are
  unanticipated.
• If the player can predict with some measure of
  certainty what the game will do, the fun in the
  game quickly disappears.

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Enemy DesignBe Unpredictable
Screen shot from Starcraft. Strategy games
benefit greatly fromunpredictability. It does
not take long for a seasoned player to
recognize the same strategy over and over again.
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Enemy DesignBe Unpredictable

• Successful unpredictability can take many forms,
  depending on the game.
• Usually, this involves adding some element of
  randomness to the games artificial intelligence.
• Could be pure randomness.
• Could be a form of selection in which there are
  several valid choices of action that are chosen
  from randomly. Weights can be applied to vary
  the amount of randomness.
• In the end, the player will never know the action
  was random, and will tend to attribute it to some
  intelligence with a purpose.

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Enemy DesignBe Unpredictable
Screen shot from Unreal Tournament 3. Enemies
can act inan unpredictable fashion through
pseudo-randomly selecting a weaponto use, and
use tactics appropriate to that weapon.
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Enemy DesignBe Unpredictable

• Keep in mind that unpredictability should enhance
  the challenge presented by the artificial
  intelligence in a game.
• If things are so random that the game cannot put
  together a solid plan for defeating the player,
  you have gone too far.
• Make sure that random choices are still realistic
  given the scenario.
• If an opponent is about to win, and its
  artificial intelligence randomly selects a poor
  action, this will seem ridiculous.

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Enemy DesignPrecomputation is Good

• Good artificial intelligence to drive your
  enemies can be computationally expensive to
  provide at run-time.
• Scarce resources are also needed for graphics,
  animation, physics, networking, and other
  subsystems though.
• Precomputation should be used wherever possible
  to provide good AI cheaply.
• Scripting of sequences of actions.
• Navigation through game terrain.
• Collisions with obstacles.

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Enemy DesignPrecomputation is Good
Screen shot from Thief II. This game uses
navigation meshes to help characters navigate
terrain. By precomputing these in advance, and
usingthem in level design, character artificial
intelligence is simpler and cheaper.
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Enemy DesignTimeouts and Fallbacks

• Nothing looks worse than a character that
  repeatedly does the wrong thing over and over.
• Players will not notice them make a wrong turn,
  but they will notice continuous collisions with
  an easy to navigate obstacle.
• Every artificial intelligence system should check
  for success conditions within a reasonable amount
  of time.
• If a timeout occurs, the system should give up
  and try something different.
• At a minimum, it can fall back to interesting
  idle animations that express its confusion or
  frustration while a new plan is formulated in the
  background.

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Enemy DesignTimeouts and Fallbacks
Screen shot from Grand Theft Auto. Police were
notoriously bad at moving around stopped
vehicles to arrest the player they could easily
get stuck or run back and forth. Timing out and
falling back would have been good.
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Enemy DesignAvoid Story Interference

• If an enemy character in a game interferes with
  the games story in its pursuit of the player,
  this is unacceptable.
• Characters must be aware of events that are
  important to telling the story.
• This includes conversations, listening to
  dialogue, watching a cut-scene, and solving game
  puzzles.
• The character should know it should back off and
  not get in the way.

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Enemy DesignAvoid Story Interference
Screen shot from Oni. Konoko was having a
conversation with the scientist inthe lab coat
when she was viciously interrupted.
Unfortunately, she missedthe rest of the story.
The guard was punished appropriately.
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Enemy DesignProvide Memories

• Enemy characters in a game should remember what
  has happened to them and others during a game.
• They can then change their behaviour and dialogue
  accordingly.
• This gives the player a sense that they are
  living beings with thoughts and feelings.
• If the artificial intelligence in a game can
  learn and adapt from its memories of events, so
  much the better.

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Enemy DesignProvide Memories
Screen shot from Quake 3 Arena. Most game
characters and bots havememories. If you shoot
them and get on their bad side, they rememberit.
They will even keep grudges against each other
too!
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Enemy DesignVariety Through Data

• A variety of enemy behaviours keeps games
  interesting and entertaining.
• Providing code for each behaviour introduces
  programming, debugging, and testing headaches.
• Instead, code should provide one or a small
  handful of behaviours that are greatly
  customizable through data. This is sometimes
  called data driven design.
• Designers can then introduce a new behaviour by
  tuning these variables.
• This includes awareness, speed, tactics, weapon
  preference, field and range of view, inventory,
  strength, abilities, chatter, and so on.
• This data should be available to designers to
  assist in game balancing and adjustments.

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Enemy DesignVariety Through Data
Screen shot from Unreal Tournament. It provides
a wide variety of bot behaviours based on the
settings of a few parameters.
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Enemy DesignPutting It All Together
Movie from Far Cry, built on the Crytek Engine.
It exemplifies a lotof the goals of good game
enemy AI in action.
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Enemy DesignPutting It All Together
Video from Devastation (courtesy of TechTVs
X-Play). A good exampleof video game AI put
together the wrong way. Big time.
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Puzzle Design

• Puzzles can be a very important type of challenge
  to many games.
• Good puzzles contribute to plot, character, and
  story development.
• Bad puzzles, on the other hand, are intrusive and
  obstructionist in nature.
• Good puzzles can help establish immersion. Bad
  puzzles can throw you out of immersion just as
  quickly.

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Types of Puzzles

• The art of puzzle design lies in the ability to
  create an original set of problems and solutions
  appropriate to the game world.
• Despite similarities, there are several different
  classifications of puzzles.
• The best games will use a variety of different
  kinds of puzzles to engage the player.

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Types of Puzzles

• Ordinary use of an object.
• One of the simplest puzzles of all.
• The player simply uses an object in the way it
  would ordinarily be used.
• The challenge in these puzzles usually comes from
  finding the object, rather than figuring out what
  is needed.
• To make things interesting, sometimes these
  objects are protected by another puzzle, or an
  enemy that must be defeated first.

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Types of Puzzles
Screen shot from Doom. Collecting the keys was
critical to unlocking doorsto continue in the
game, but wasnt a very difficult problem to
figure out. Figuring out how to actually get
the keys was often a different story!
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Types of Puzzles

• Unusual use of an object.
• Unusual use takes advantage of objects secondary
  characteristics.
• It requires players to recognize that things can
  be used in ways other than their creator had
  intended.
• In this case, the trick is not so much in
  acquiring the objects to use, but in figuring out
  how to make appropriate use of them.

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Types of Puzzles
Screen shot from Splinter Cell. Sticky cams were
not only good for surveillance. A well aimed shot
to the head would knock a guard out, and the
cameracould be reused again and again! Bonus!
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Types of Puzzles
Screen shot from Psi-Ops The Mindgate
Conspiracy. In this game, guards can also be
used as handy dandy glass breakers. Sweet!
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Types of Puzzles

• Building puzzles.
• In this case, the player is required to create a
  new object out of raw materials that are
  available in the game.
• This can involve converting one object into
  another, or by combining two or more objects
  together to make something new.
• Be careful not to assume the player will know
  what to build and how to build it. Some guidance
  might be necessary here.

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Types of Puzzles
Screen shot from Maniac Mansion. One puzzle in
this game had you build a ladder by feeding a
man eating plant Pepsi. This caused the plantto
hiccup and extend itself up to the floor above.
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Types of Puzzles

• Information puzzles.
• In these puzzles, the player must supply a
  missing piece of information.
• It could be as simple as providing a password, or
  as complex as deducing the sequence of numbers to
  deactivate a bomb.
• Finding the information might require talking to
  other characters, searching through documents, or
  deducing the information based on who or what is
  requiring it.

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Types of Puzzles
Screen shot from Zork. Later in the game, you
encounter a Cyclops.Entering the name Odysseus
or Ulysses will cause the otherwise
unfriendlyCyclops to run away. You could figure
out this bit of information if youread the
prayer book, or if you recall Greek mythology
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Types of Puzzles

• Excluded middle puzzles.
• This puzzle involves creating a reliable cause
  and effect relationship.
• It requires the player to recognize an action
  will kick off a chain of events that leads to the
  desired results.
• In terms of logic, you have a causes b and c
  causes d. When the player is in a situation that
  requires d, hopefully the player will realize b
  and c are linked, and perform a.

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Types of Puzzles
Screen shot from Maniac Mansion. The chandelier
contains a key you need laterin the game. It is
made of glass and appears fragile. Elsewhere,
you discovera record with glass shattering
properties. By recording the sound to a
blanktape, and playing the tape here, you can
shatter the chandelier and get it to fall to
give you the key! A tricky excluded middle
puzzle.
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Types of Puzzles

• People puzzles.
• Involve dealing with game characters to remove
  the obstacles they present.
• Typically work by giving the character something
  they want, talking to them, or some other
  interaction.
• Timing puzzles.
• Require the player to take an action without an
  immediate desired effect, but causes something to
  happen at a particular point in the future.

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Types of Puzzles
Screen shot from Stolen. Among Anyas gadgets is
the sonic emitter. When deployed, it can later
be activated to distract guards. If timed
properly, this can lure them away from their
posts, allowing her to sneak by undetected.In a
way, both a people puzzle and a timing puzzle.
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Types of Puzzles

• Sequence puzzles.
• Rely on the player performing a series of actions
  in just the right order.
• Usually starts with the player trying a simple
  action to solve a puzzle, and something pops up
  to prevent that solution from working.
• The situation then resets.
• The player must then try again, putting something
  in place to deal with the new problem before
  restarting the sequence.
• This can become quite elaborate!

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Types of Puzzles
Screen shot from the Hitchhikers Guide to the
Galaxy 20th Anniversary Edition. Depicted here
is the result of solving the babel fish puzzle
a classic example of a sequencing puzzle.
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Types of Puzzles

• Logic or deduction puzzles.
• The player must formulate a deduction by
  examining information and ferreting out a hidden
  implication.
• Classic gaming puzzles.
• Things like the magic square, tile sliding, peg
  jumping, matchstick moving, and so on.
• These are not true action or adventure game
  puzzles, but they often find their way into these
  games in various forms.

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Types of Puzzles
Screen shot from Death Gate. In this adventure
game, you had tomanipulate a device, crafted by
Dwarves, into a certain configurationbefore you
could gain entrance to a cave. Much like a
classic puzzle game.
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Types of Puzzles

• Riddles.
• Riddles require plenty of clues and hints.
• If the player cannot get the riddle, they can get
  stuck feeling stupid, which is a bad thing.
• Dialogue puzzles.
• Dialogue puzzles require the player to follow a
  conversation down the correct path of a dialogue
  tree until the player says or does the right
  thing to remove the obstacle.

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Types of Puzzles
Screen shot from Marvel Ultimate Alliance.
Before this boss fight with M.O.D.O.K., he asks
you questions and riddles that, if answered
correctly, can make your boss fight easier. If
missed, you can still proceed, just witha harder
fight on your hands.
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Types of Puzzles
Screen shots from Law of the West. This game
consisted of traversingthrough a series of
dialogue trees and gunfights, if necessary,
depending onthe conversation. Or, if youre
like me, even when they werentso necessary
after all!
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Types of Puzzles
Screenshot from Vampire The Masquerade
Bloodlines. One of thecharacter classes in this
game is a little well, insane, allowing you to
engagein a dialogue tree with things like this
stop sign. How cool is that?
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Types of Puzzles

• Machinery puzzles.
• The player must figure out how to correctly
  operate machinery for some purpose.
• Sometimes it involves minor trial and error,
  along with a dose of logic and deduction.
• Mazes.
• Mazes used to be a staple of adventure games,
  requiring people to map them with pencil and
  paper.
• Over time, they have become a cliché, and so you
  should only create one if you have developed an
  interesting and unique twist to the idea (for
  example in mapping, navigating, and so on).

68
Types of Puzzles
Screen shot from Resident Evil 4. Inside the
building at the top of thishill is a machinery
puzzle where you have to reproduce the
correctcolour pattern on the wall.
Incidentally, theres another machinerypuzzle
behind the building too that will give you some
treasure!
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Types of Puzzles
Screen shot from Advanced Dungeons and Dragons
for the Intellivision. This classic game
consisted of navigating multiple dungeon mazes,
fightingmonsters, and looking for treasure and
items. Very good foreshadowingand hints to
enemies too in its randomized level design!
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Types of Puzzles
Screen shot from ADD Treasures of Tarmin for
the Intellivision. Another game with lots of
randomly generate mazes to navigate through,this
time from a first person perspective.
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Types of Puzzles
Screen shot from Legacy of the Ancients. Another
adventure gameheavily consisting of maze
navigation. Still a pretty fun game though!
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What Makes a Bad Puzzle?

• Good puzzle design involves looking into the
  world created and using obstacles, objects, and
  characters that would naturally occur in that
  environment.
• Puzzles that do not do this do not fit well into
  the game and break immersion.
• A puzzle requiring the player to fail first in
  order to succeed later is a bad one.
• The player should have all the tools needed to
  solve a puzzle when the time comes.

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What Makes a Bad Puzzle?

• Effects should be linked to causes. If you can
  remove an obstacle and not know why, that is
  indicative of a bad puzzle.
• Puzzles that make sense only to the designer must
  be avoided.
• Good play testing should uncover these.
• Avoid binary puzzles that yield only instant
  success or failure.
• Give the player lots of choices and let them
  explore.
• Avoid hunt the pixel problems. If something is
  important, make it reasonably hard to miss.

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What Makes a Bad Puzzle?

• Other things to avoid
• Puzzles solvable only by trial and error.
• Conceptual non sequiturs that make so little
  sense that they are only solvable by luck or by
  accident.
• Illogical or impossible spaces that cannot exist
  or cannot be mapped properly.
• Puzzles requiring outside knowledge.
• Too many backward puzzles, where the solution is
  found before the puzzle.
• Too many FedEx puzzles in which you just have to
  move objects around from place to place.

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What Makes a Good Puzzle?

• Fairness.
• The answer to every puzzle should be contained
  within the game.
• A player should be able to theoretically solve a
  puzzle on the first attempt if enough thought is
  put into it.
• Appropriateness.
• A good puzzle fits the setting and advances the
  story upon completion.
• Amplifying the theme.
• A good puzzle should work with the theme of the
  story, not against it.

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Levels of Difficulty

• There are several ways to tune the difficulty of
  a puzzle.
• Change the amount of information provided to the
  player, or how it is presented.
• Change the distance between the solution to the
  puzzle and the puzzle itself.
• Allow for alternate solutions to a puzzle to make
  it easier.
• Include red herrings to increase difficulty.
• Change how much the player is steered towards the
  puzzles solution.

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How to Design a Puzzle

• A game is broken down into levels, each with its
  own goal. By completing all goals, the game
  itself is completed.
• Each goal must have an obstacle preventing the
  player from easily reaching it.
• These obstacles can be the puzzles thatwould
  occur in the game.
• They should fit into the story and in the
  setting, and the player should have reasonable
  ways of solving them.

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How to Design a Puzzle

• The easiest way to develop puzzles in a game is
  to think about the villain.
• The villain is actively opposed to the player
  succeeding, and will be the one using obstacles
  to try to stop them.
• Think of how the villain would actually try to
  stop the player.
• Keep in mind what raw materials the villain would
  have in creating the obstacle.
• Keep in mind what the villain knows as well.

79
How to Design a Puzzle
Screen shot from Rune. This is a puzzle to cross
the lava pit, something Hel might just make you
do.
80
How to Design a Puzzle

• Player empathy is a key factor in puzzle design.
• You must be able to see things from the players
  point of view to determine what is reasonable and
  what is not.
• This will also let you see how the player would
  attempt to solve a puzzle, so the game can react
  appropriately.
• The game should be set up so that it is clear
  when the player is facing a puzzle, and when the
  player is just going in the wrong direction.
• With empathy, you can provide appropriate clues
  and steering to help the player out.