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Anatomy of a 2D Sidescroller Luis Barriga Before we start Please turn off cell-phones and pagers. Save your questions for Q&A after lecture. Turn in feedback forms before you leave. Introduction Purpose of Lecture Establish that 2D is a format and not a technology limitation.

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before we start
Before we start
  • Please turn off cell-phones and pagers.
  • Save your questions for Q&A after lecture.
  • Turn in feedback forms before you leave.
  • Purpose of Lecture
    • Establish that 2D is a format and not a technology limitation.
    • Propose the analysis of 2D games as a tool for understanding universal gameplay fundamentals.
    • Dissect the common components of 2D games as well as their evolution throughout time.
lecture at a glance
Lecture at a glance
  • On having more D’s
  • Elements of a 2D sidescroller
  • 10 Model games
on having more d s
On having more D’s
  • 2D as a technological limitation
  • Immersion vs. abstraction
  • Ambiguity in representing 3D in 2D media
  • 2D and 3D as presentation formats
on having more d s6
On having more D’s
  • 2D as a technological limitation
    • Since the mid-90’s, 3D has been seen as an improvement over 2D. “The next step”
    • 3D capable platforms are more technologically advanced, thus not using 3D is often seen as a “waste.”
    • Even in very 2-d specific platforms, rudimentary 3d engines are often seen as a tool for differentiation.
on having more d s7
On having more D’s
  • Immersion vs. abstraction
immersion vs abstraction
Immersion vs abstraction
  • We experience the real world in 3d
  • We communicate abstractions in 2d
    • Letters
    • Maps
    • Symbols
    • Charts
    • Diagrams
immersion vs abstraction9
Immersion vs abstraction
  • Spatial perception
    • The ability to mentally model/manipulate 3D images.
    • A skill that human beings develop over time (and are even tested on), it is a factor that must be considered when designing a game

An example of a spatial perception test taken from

immersion vs abstraction10
Immersion vs abstraction
  • A thought on gender
    • Psychologists have found that males have an advantage at spatial perception and object displacement. Even about finding their way around maps.
    • They’ve also found that females have an advantage at remembering landmarks.
    • I am not a psychologist.

on having more d s11
On having more D’s
  • Ambiguity in representing 3D in 2D media
ambiguity in representing 3d in 2d
Ambiguity in representing 3D in 2D
  • Technology impediment
    • Unless a less ambiguous 3d medium becomes commonplace (VR goggles, Star Wars’ Dejarik chesslike holographic display), the “tightness” of gameplay will not be the same in 3D as 2D.
    • To compensate games must often add a lot more room for error, snapping or automatic guidance.
ambiguity in representing 3d in 2d13
Ambiguity in representing 3D in 2D
  • Format difficulties
    • Making sure objects are recognizable at any angle
    • Mediation (Camera) issues (3rd person for example)
on having more d s14
On having more D’s
  • 2D and 3D as presentation formats
    • We should start looking at 3D vs 2D as a choice of formats that will enhance different types of gameplay.
    • 3D -> Immersion
    • 2D -> Abstraction + pixel level accuracy
on having more d s15
On having more D’s
  • 2D and 3D as presentation formats
    • Quite a few games have been pursued a 2D presentation on 3D platforms
      • Castlevania: Symphony of the night
      • Viewtiful Joe
      • Contra: Shattered Soldier
      • R-type Final
    • And more are sure to come ;-)
elements of a 2d sidescroller
Elements of a 2D sidescroller
  • The character
  • The environment
  • Game objects
  • Game rules
  • Mediation
elements of a 2d sidescroller19
Elements of a 2D sidescroller
  • Note
    • Although we can dissect sidescrollers into components, more often than not elements are designed in parallel. For example: designing a grappling hook toss also requires designing environment types that enable this move.
elements of a 2d sidescroller20
Elements of a 2D sidescroller
  • The character
    • From a gameplay standpoint here’s what interests us about the character:
      • Set of available actions
      • Visual footprint: shape/size, its visibility and its ratio to the screen and other objects
elements of a 2d sidescroller21
Elements of a 2D sidescroller
  • Action sets
    • Interactivity is the core of what defines games: “what do you do in the game?” vs “what is the movie about?”
    • Game characters are defined as much by their available actions as by the character’s looks.
elements of a 2d sidescroller22
Elements of a 2D sidescroller
  • Example:
    • I can shoot beams and missiles
    • I roll into a ball
    • I can freeze enemies to use them as platforms
  • Metroid’s Samus Aran
designing action sets
Designing Action Sets
  • Actions types
    • Generic (running, jumping, attacking)
    • Game-specific
  • Conventions
    • With a genre as well explored as side-scrollers, many actions have conventions associated with them
    • Feel free to ignore or work outside conventions but do so consciously (especially with core actions)
designing action sets24
Designing Action Sets
  • Example: Jumping
    • Pre-scroller fixed jump
    • Variable jump
jumping conventions26
Jumping Conventions
  • Button Assignment
    • B is action, A is jump
  • Variable jumping, Y
    • 2-tier jump
    • Gravity delay
    • Velocity reset (direct control feel)
  • Variable jumping, X
    • Direct control (character moves when directed)
    • Indirect control (changes acceleration)
running conventions
Running Conventions
  • Mainstream controls don’t always become conventions
    • Example 1: holding action button for running (Mario games)
      • Double tap d-pad became convention
      • In modern games shoulder button became convention
    • Example 2: Up + Action button for secondary action (Ninja Gaiden, Castlevania)
damage conventions
Damage conventions
  • Touch damage model
    • Character takes damage whenever coming in contact with enemy (regardless of whether the enemy is attacking or not)
  • Brawler model
    • Characters only deal damage when attacking
  • Intermediate models
    • Shinobi, Kung Fu, others. Touching an opponent leads to either mutual repulsion with no damage or a “captured” state with slow damage.
designing action sets31
Designing Action Sets
  • Game-specific actions
    • Refer to the greater vision or theme of the game to come up with suitable actions.
    • Bruce Lee: Formidable fighting and acrobatic prowess -> deep combo tree, wall flip, pole slide, etc.
    • Brother Bear: Animal vs. Nature -> Water sliding, balancing on logs.
  • Shape
  • Visibility
  • Size ratio
  • Mental models and Game Engines
    • Characters in collision engines are usually represented as a box or collections of boxes
    • The player will develop his/her own mental model for the way the game world works.
    • A good correlation between the two will lead to a feeling of “tightness” in gameplay
    • A disconnection in the two will lead to sloppy gameplay.
  • Visibility
    • Player characters need to be distinguishable not just from the background but also from all other game objects.
    • Player characters actions and reactions need to be distinguishable from each other.
  • Size Ratio
    • The size of a character cannot be judged in an isolated manner.
    • We need to consider the ratio of a character’s size to:
      • The screen
      • The character’s actions’ visual footprints
      • Other objects
size ratio vs screen
Size Ratio – vs Screen
  • A screen must fit:
    • A character centered roughly on the bottom leftmost third of the screen.
    • A character’s full jump arc
    • A complete or near-complete encounter
      • Example: a bare pit must have both of its ledges visible. A pit with an enemy threatening one of the ledges must also account for the enemy’s patrol range.
    • HUD and so on.
size ratio vs actions
Size Ratio – vs Actions
  • Ratio vs Jump
    • Jumps are usually tall enough to clear at least one character unit (so you can jump over equivalent enemies).
    • Jump should be small enough to not exceed the screen size of a centered character as it’s a convention to lock the camera through the natural arc of a jump.
size ratio vs actions40
Size Ratio – vs Actions
  • Ratio vs. Attacks
    • Aim for your attacks to extend at least around one character unit out.
  • The Environment
    • The environment can only be analyzed within the context of handling.
    • A Mario level will play very differently with Spider-man as a player character.
  • Building levels
    • There are many approaches to building levels.
    • It’s always good to prototype a level before dedicating art to it.
    • Building metrics. The character’s actions imply metrics, good levels take these into account.
building levels continued
Building levels (continued)
  • Build encounters
    • Encounters are group of environment sections and game objects that need to be considered by the player in conjunction
    • Once an encounter works, use it as a building block.
building levels continued46
Building levels (continued)
  • Build a narrative
    • Sometimes you just have a strong vision of “moments” of gameplay.
    • In these cases linking these in a narrative form and translating the narrative into a level works well.
building levels continued47
Building levels (continued)
  • Example:
    • Bears sliding down waterslide.
    • Bears getting shot off the end of the waterslide.
    • Bears landing directly into a balancing act position.
    • This led me to design a level where you slide down a long section, avoiding rocks, collecting berries, get shot off the end of the waterslide and landed on a log.
building levels continued48




Building levels (continued)
  • Metrics
building levels continued49
Building levels (continued)
  • Jump Metrics
    • Jump height
    • Jump reach
    • Jump width
  • Other Metrics
    • Landing space
    • Crawl space
game objects
Game Objects
  • What are they?
    • Game objects are everything that the player character (the subject) acts upon.
    • Enemies, breakables, collectibles, doors, etc.
game objects52
Game Objects
  • Here’s something key:
    • If your objects only provide your player with one action the game will “play itself”
    • Having dual or multiple use objects, allows the player to make choices and increases the the depth of your gameplay.
    • Examples: Samus can blast an enemy or she can freeze it and use it as a platform. Mario can hop on a turtle and leave it or he can kick the shell towards other enemies.
game objects54
Game Objects
  • Use them to magnify player character actions
    • Problem: Bruce Lee – We wanted combat to be engaging, but foot soldiers to not be very threatening (except in numbers).
    • We focused on giving enemies interesting ways to be beat up.
      • Height and direction sensitive hit animations
      • Disarms
      • Using enemies as projectiles
  • Very, very broad topic
  • Victory and defeat conditions
  • Rules governing saving and retries
  • Associated conventions
    • Falling off the bottom of the screen
    • Exiting at the rightmost end of a level
  • Come up with rules that engage the player at different levels
    • Damage model -> immediate well being of character
    • Skill tree -> strategic advancement of character
    • Time limit -> urgency for completion of goal
    • X Collectibles to do Y -> medium term objective
    • Points and currency -> long term or lateral goals (secrets unlockables, etc.)
  • Camera
    • Centering
    • Scaling
  • Views
    • Straight 2D
    • Floor-tilt view
    • Cabinet
  • Camera… what camera?
    • Believe it or not, cameras in 2D games aren’t freebies.
    • You only really notice a camera if it’s bad.
    • A good sidescroller camera focuses on what the next encounter is going to be (above and ahead of the character).
  • Centering
    • As mentioned before, focus more on what is to come than what has passed already.
    • This basically means centering the character in the lower third of the screen with the horizontal space divided 1/3 behind it and 2/3 ahead of it.
    • Also as stated before this should give the player a good view of encounters to come.
  • Scaling
    • Limited platform support in 2D platforms (SNES, Neo Geo, Game Boy Advance)
    • Sacrifices certain features (less layers, less sprites)
    • Allows you to depict larger encounters (or even multiple encounters) in their entirety by zooming the action out when needed.
views for non 3d graphic engines
Views (for non-3D graphic engines)
  • Straight-on 2D
    • Every orthogonal surface is a line (i.e. you can’t see walls, ceilings or floors)
views for non 3d graphic engines63
Views (for non-3D graphic engines)
  • Floor-tilt view
    • Same as straight-on view but “fake” the angle so the player can see the floor.
  • Cabinet view
    • The cabinet view is probably the hardest to implement.
    • It consists of a view similar to the full-on 2D view but the player can see the wall and the floor.
10 model games
10 model games
  • Not the best or most well known
  • Offer a good variety of examples for reference
  • Come up with your own set of model games
10 model games69
10 model games
  • Game: Batman
  • System: NES
  • Why?
    • Tightest wall jump in any game
    • Greatest game over music ever
10 model games71
10 model games
  • Game: Strider
  • System: Arcade/Genesis
  • Why?
    • Sloped terrain with matching leg movement
    • Wall clinging and hand over hand action
    • Gravity reversal
    • Swooshes!!
    • Shinobi or Ninja Gaiden will also work as action game templates
10 model games72
10 model games
  • Game: Metroid
  • System: NES
  • Why?
    • Interconnected levels
    • Linking of skills progression with level progression
10 model games74
10 model games
  • Game: Contra IV, the Alien Wars
  • System: SNES
  • Why?
    • Special FX
    • Bosses
10 model games75
10 model games
  • Game: Ghouls and Ghosts
  • System: Arcade, SNES, Genesis
  • Why?
    • Dynamic terrain
    • Difficulty benchmark (if your game is harder than this, you’re screwed)
10 model games76
10 model games
  • Game: Bionic Commando
  • System: NES
  • Why?
    • Example of a game that does without one of the core sidescroller mechanics (jump) successfully.
10 model games78
10 model games
  • Game: Double Dragon I
  • System: Arcade, NES, Genesis
  • Why?
    • Ok, so it’s not a 2D game (2.5D)
    • Establishes the brawler damage model as well as you need to understand it.
    • The entire series (except 5) can be looked at for progression in variations.
10 model games79
10 model games
  • Game: Mega Man
  • System: NES, SNES
  • Why?
    • Swappable action sets
10 model games80
10 model games
  • Game: Lost Vikings
  • System: SNES
  • Why?
    • Single-player multi-character puzzles
10 model games82
10 model games
  • Game: Super Mario All-Stars
  • System: SNES
  • Why?
    • Because all you need to know is probably here.

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