Anatomy of a 2D Sidescroller

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Anatomy of a 2D Sidescroller

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Title: Anatomy of a 2D Sidescroller

1
Anatomy of a 2D Sidescroller

Luis Barriga

2
Before we start

Please turn off cell-phones and pagers.
Save your questions for QA after lecture.
Turn in feedback forms before you leave.

3
Introduction

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.

4
Lecture at a glance

On having more Ds
Elements of a 2D sidescroller
10 Model games

5
On having more Ds

2D as a technological limitation
Immersion vs. abstraction
Ambiguity in representing 3D in 2D media
2D and 3D as presentation formats

6
On having more Ds

2D as a technological limitation
Since the mid-90s, 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.

7
On having more Ds

Immersion vs. abstraction

8
Immersion vs abstraction

We experience the real world in 3d
We communicate abstractions in 2d
Letters
Maps
Symbols
Charts
Diagrams

9
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 http//www.exn.ca/brain/tests/
10
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.
Theyve also found that females have an advantage
at remembering landmarks.
I am not a psychologist.
http//www.unn.ac.uk/academic/ss/psychology/resour
ce/py095/LECTURE7.HTM
http//www.psychology.mcmaster.ca/3l03sun/2000-200
1W/spatial/0_Group_Game_FinalReport2.htm
http//psychology.unn.ac.uk/nick/HPlec06.htm

11
On having more Ds

Ambiguity in representing 3D in 2D media

12
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.

13
Ambiguity in representing 3D in 2D

Format difficulties
Making sure objects are recognizable at any
angle
Mediation (Camera) issues (3rd person for
example)

14
On having more Ds

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

15
On having more Ds

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 -)

16
On having more Ds
17
On having more Ds
18
Elements of a 2D sidescroller

The character
The environment
Game objects
Game rules
Mediation

19
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.

20
Elements of a 2D sidescroller

The character
From a gameplay standpoint heres 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

21
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 characters looks.

22
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
Metroids Samus Aran

23
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)

24
Designing Action Sets

Example Jumping
Pre-scroller fixed jump
Variable jump

25
Jumping conventions
26
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)

27
Running Conventions

Mainstream controls dont 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)

28
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.

29
Damage conventions
30
Damage conventions
31
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.

32
Designing Action Sets
33
Visuals

Shape
Visibility
Size ratio

34
Visuals

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.

35
Visuals
36
Visuals

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.

37
Visuals

Size Ratio
The size of a character cannot be judged in an
isolated manner.
We need to consider the ratio of a characters
size to
The screen
The characters actions visual footprints
Other objects

38
Size Ratio vs Screen

A screen must fit
A character centered roughly on the bottom
leftmost third of the screen.
A characters 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 enemys
patrol range.
HUD and so on.

39
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 its a
convention to lock the camera through the natural
arc of a jump.

40
Size Ratio vs Actions

Ratio vs. Attacks
Aim for your attacks to extend at least around
one character unit out.

41
Environment
42
Environment

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.

43
Environment
44
Environment

Building levels
There are many approaches to building levels.
Its always good to prototype a level before
dedicating art to it.
Building metrics. The characters actions imply
metrics, good levels take these into account.

45
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.

46
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.

47
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.

48
Building levels (continued)

Metrics

49
Building levels (continued)

Jump Metrics
Jump height
Jump reach
Jump width
Other Metrics
Landing space
Crawl space

50
Building levels (continued)
51
Game Objects

What are they?
Game objects are everything that the player
character (the subject) acts upon.
Enemies, breakables, collectibles, doors, etc.

52
Game Objects

Heres 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.

53
Game Objects
54
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

55
Rules

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

56
Rules

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.)

57
Mediation

Camera
Centering
Scaling
Views
Straight 2D
Floor-tilt view
Cabinet

58
Camera

Camera what camera?
Believe it or not, cameras in 2D games arent
freebies.
You only really notice a camera if its bad.
A good sidescroller camera focuses on what the
next encounter is going to be (above and ahead of
the character).

59
Camera

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.

60
Centering
61
Camera

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.

62
Views (for non-3D graphic engines)

Straight-on 2D
Every orthogonal surface is a line (i.e. you
cant see walls, ceilings or floors)

63
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.

64
Views

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.