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Eyez: Spatial perception in videogames

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Eyez: Spatial perception in videogames

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EYEZ:
SPATIAL PERCEPTION IN VIDEOGAMES

by

Hua Chen
_______________________________________________________________

A Thesis Presented to the
FACULTY OF THE USC SCHOOL OF CINEMATIC ARTS
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF FINE ARTS
(INTERACTIVE MEDIA)

May 2011

Copyright 2011 Hua Chen

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Acknowledgements
I would like to thank the faculty, staff and students of the Interactive Media Division for their
support of Eyez. Thank you to Fox Interactive for granting me the 2010 Fox Interactive Thesis
Fellowship to fund this project. Thank you to Microsoft Research and Microsoft Game Studios for
providing me with the Windows Phone 7 devices. Thank you my advisors Chris Swain, Peter
Brinson, Kim Swift and John Hight. Chris, thank you for all your support, advisement and critical
review ever since the conceiving of this thesis in early 2010. Peter, thank you for encouraging
this idea from the beginning when it was still a primitive Torque2D prototype and all the valuable
feedback you gave me. Kim, thank you for your insightful guidance and the “Less is More” design
philosophy you shared with me. John, thank you for your expertise and instructions on game
production and creating a better user experience.
Thank you to my teammates Yang Liu, Elizabeth Swensen, Anoop Kamboj, Andrea Chang.
Yang, thank you for the beautiful animations and art assets. Elizabeth, thank you for the
well-written story and scripts. Anoop, thank you for helping me by coding some of the additional
screens. Andrea, thank you for creating the ethereal music and sound.
Thank you to the professors of the CTIN594 class: Mark Bolas, Jeremy Gibson, and Anne
Balsamo, for all the help and support you offered during this whole year.
Thanks to all the USC faculty, staff, students, graduates and friends who donated their
time to bring Eyez to life: Steve Anderson, Adrienne Capirchio, Benjamin Chang, David Hollin,
Yaojun Huang, Yang Liu (male), Daniel Ponce, Sam Pierce, Michael Sheehan.
Thank you for Dr. Zhao Chen Ding’s inspiring doctoral dissertation and Prof. Zhiyong Fu’s
extra game design assignment when I was back in Tsinghua University, China.
And finally thanks to my father Guosheng Chen and my mother Mei He. I would not have
been able to do all this without your constant love, support and encouragement.

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Table of Contents
Acknowledgements ................................................................................................ ii
List of Figures ........................................................................................................v
Abstract ................................................................................................................ vi
1 Introduction ................................................................................................ 1
1.1 Background and Concept for This Project ..................................................... 1
2 Project Description ..................................................................................... 3
2.1 Prior Art Review ........................................................................................... 3
2.2 Core Mechanics ........................................................................................... 7
2.2.1 Screen-wrapping ..................................................................................... 7
2.2.2 Screen-locking ......................................................................................... 7
2.3 Story ............................................................................................................ 8
2.4 Control Scheme ........................................................................................... 9
2.4.1 Walking ................................................................................................... 9
2.4.2 Jumping .................................................................................................. 9
2.4.3 Triggering the Eyez ability ..................................................................... 10
3 Core Game Objectives .............................................................................. 11
4 Story and User Experience Description ..................................................... 12
4.1 The Forgotten Garden ................................................................................ 12
4.1.1 Story ..................................................................................................... 12
4.1.2 User Experience .................................................................................... 12
4.2 The Lonely Peak ........................................................................................ 13
4.2.1 Story ..................................................................................................... 13
4.2.2 User Experience .................................................................................... 14
4.3 The Prison of the Past ................................................................................ 15
4.3.1 Story ..................................................................................................... 15
4.3.2 User Experience .................................................................................... 16
4.4 The Waking Worl d ...................................................................................... 16
4.4.1 Story ..................................................................................................... 16
4.4.2 User Experience .................................................................................... 17
5 Development Process ............................................................................... 18
5.1 Digital Prototyping using Torque2D Game Engine ....................................... 18

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5.2 Development using XNA Game Studio ........................................................ 19
6 Playtesting and Evaluati on ........................................................................ 22
7 Dis c u s s i on ................................................................................................ 24
7.1 Interesting findings about videogame space ................................................ 24
7.1.1 Avatar, and the sense of size and scale ................................................. 24
7.1.2 Spatial consistency, loading, navigation and maps ................................. 25
7.1.3 Cognitive Illusions ................................................................................. 26
7.1.4 Tinkering with Spatial Rules ................................................................... 26
7.1.5 Spatial Perception based on the Screen ................................................. 27
7.2 Next Steps ................................................................................................. 28
8 Conclusion ............................................................................................... 29
Glossary ............................................................................................................. 31
Bibliography ........................................................................................................ 32

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List of Figures
Figure 2.1 Portal (From http://wikipedia.org and http://thierrygagnon.com) ......... 4
Figure 2.2 Crush (From http://cinemablend.com and http://crispygamer.com) ..... 4
Figure 2.3 Echochrome (From http://pcprofessionale.it) ..................................... 5
Figure 2.4 Shift (From http://slidetoplay.com)..................................................... 5
Figure 2.5 Unfinished Swan (From http://giantsparrow.com ) ............................... 6
Figure 2.6 Miegakure (From http://marctenbosch.com/miegakure/) ..................... 6
Figure 2.7 Illustration of screen-wrapping in Pac-Man ........................................ 7
Figure 2.8 Illustration of screen-locking in Breakout ........................................... 8
Figure 2.9 Control for Walking ........................................................................... 9
Figure 2.10 Control for J u mping ..................................................................... 10
Figure 2.11 Traversing and Wall-jumping ....................................................... 10
Figure 4.1 Using a Statue to Perform Traversing .............................................. 13
Figure 4.2 How Projectiles Move in Blue-Eye Mode and Red-Eye Mode ........... 14
Figure 5.1 Screenshot of the Torque2D prototype of Eyez ................................ 18
Figure 5.2 3-view of the protagonist Mint in the WP7 version of Eyez ............... 20
Figure 5.3 Screenshot of the WP7 version of Eyez (WIP) ................................. 21
Figure 6.1 People playing Eyez on WP7 devices during the Winter Show 2010 . 23

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Abstract
Today, with the support of increasingly powerful hardware and software, we can almost
recreate photorealistic reproductions of our physical world. Many videogame developers are still
trying to design and build worlds in their games based on the spatial rules and common sense in
the physical world in order to offer more “authenticity”. Eyez is a 2D action/puzzle game where
players are required to think and play based on the spatial logic set in the game that intentionally
explores and utilizes “unauthentic” spatial perception. The goal of this project is to create new
and satisfying user experiences in game space other than just simply transferring existing
“authentic” experiences from physical space into game space. By simply adding the option for the
player to switch the game space between the Blue-Eye Mode (Screen-wrapping Mode) and the
Red-Eye Mode (Screen-locking Mode), a traditional 2D platformer game can offer a totally
different gaming experience from its peers.

Keywords
Spatial Perception, Spatial Cognition, Spatial Design, Visual Perception, Windows Phone, XNA,
Video Game, Platformer, Puzzle Game

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1 Introduction
1.1 Background and Concept for This Project
Today, videogames are reaching maturity as a new media and a new type of entertainment.
With the support of increasingly powerful hardware and software, we can almost recreate
photorealistic reproductions of our physical world. Many game developers are still trying to
design and build worlds in their games based on the spatial rules and common sense of the
physical world. Photorealistic graphics, convincing physics and other new technologies such as
seamless loading and stereoscopic displays are being implemented in more and more
videogames, all of which are the efforts of game developers to offer more “authenticity” in the
worlds of their games.
My argument is, does more “authenticity” necessarily mean better user experiences? As
Professor Mark J.P. Wolf noted: “In the areas of representational characters, narratives, and
spaces, there were the enormous precedents set by film and television imagery. It is perhaps due
to the desire to measure up to the standards of visual realism set by film and television that the
video game evolved as it has; today there are far fewer of the abstract game designs that were
once so common in the days of Qix (1981) and Tempest (1980).” (Wolf 11-23) Resemblance of a
game’s space to the real world may be important under certain circumstances, but it is definitely
not the key to great game designs and great user experiences.
Moreover, there are more things we can do than just simply design videogame spaces in
ways that resemble the real world. This potential lies in the fact that visual perception of space is
not a passive process of one-way reception but an active process of creation. Professor Donald
D. Hoffman wrote: “Perhaps the most surprising insight that has emerged from vision research is
this: Vision is not merely a matter of passive perception, it is an intelligent process of active

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construction. What you see is, invariably, what your visual intelligence constructs. Just as
scientists intelligently construct useful theories based on experimental evidence, so your visual
system intelligently constructs useful visual worlds based on images at the eyes.” (Hoffman XII)
What we call the “game space” is actually just our spatial perception of the 2D (2-dimensional) or
3D (3-dimensional) world of the videogame, mapped from the 2D image conveyed from the flat
TV or monitor screen to our mind. This perception is actually a projection, triggered by the limited
information of the 2D images on the screen and reconstructed in our mind combining our existing
knowledge about the physical world (Fermuller, Cheong, and Aloimonos 329). This intriguing fact
suggests that there is more we can do with “game space” than merely limit ourselves to common
sense and real-life “authenticity.”
From a design point of view, I believe that there are more new and interesting possibilities
for user interaction in game space other than just simply transferring existing “authentic”
experiences from physical space into game space. By manipulating what players see on the
screen, game designers can shape players’ spatial perception in their game worlds and offer
unique user experiences that can only be found in videogames. Eyez is an attempt to exemplify
this belief.

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2 Project Description
Eyez is a 2D action/puzzle game where players are required to think and play based on
the spatial logic set in the game that intentionally explores and utilizes “unauthentic” spatial
perception. Eyez features a classic 2D platformer form in which the player character can move
and jump in a 2D world that resembles a side-camera view. Super Mario Bros. 2 and Braid are
similar in terms of basic mechanics and can be used as references. Where Eyez differs from
other 2D platformer games is that not only does it let the player explore the game world based on
the player’s existing spatial literacy learned in the physical world (mapping the real world to the
inner model in the player’s mind), but it also requires the player to perceive and navigate through
the game space based on simple and unique spatial rules (the Blue-Eye Mode and the Red-Eye
Mode) that don’t exist in the real world.

2.1 Prior Art Review
I have always been interested in games that experimented with the topic of spatial
perception and have learned quite a lot playing these games. The games below are seminal in
expanding the idea of spatial perception in videogames because of—often simple—innovations
in spatial mechanics.
The most prominent game about spatial perception is Portal (PC/Mac/Xbox360/PS3.
Website: http://www.valvesoftware.com/games/portal.html. Metacritic: 90/100), a single-player
first-person action/puzzle game that provides players with unprecedented game experience
based on one simple spatial rule: objects go into one portal and come out through another portal.
Specifically, players may create a portal exiting their current space and another portal opening an

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entry point into the same space. With this simple rule, many interesting puzzles defying our
notion about the physical world are presented to players. Portal won three awards in the Game
Developers Choice Awards 2008, as well as awards from game media such as IGN and
GameSpot.
Figure 2.1 Portal (From http://wikipedia.org and http://thierrygagnon.com)
Crush (PSP. Website: http://blogs.sega.com/europe/category/crush/. Metacritic: 83/100) is
a platformer-puzzle game that plays with the perception of 2D/3D space on screen. Players can
switch the world between 2D mode and 3D mode to solve puzzles. The core mechanic of this
game is based on the fact that we can’t perceive depth on screen at certain camera angles.
(Games with similar ideas: Super Paper Mario, Fez)
Figure 2.2 Crush (From http://cinemablend.com and http://crispygamer.com)
Echochrome (PS3/PSP. Website: http://www.echochromegame.com/. Metacritic: 81/100)
is a puzzle game that plays with the fact that what we perceive as 3D space on the screen is in
reality just 2D images. The design of this game was influenced by M. C. Escher’s artwork. In

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Echochrome, by viewing things from certain perspectives, spatial inconsistency in what we
perceive as 3D space can be neutralized, so the character can move from one platform to
another separate platform.

Figure 2.3 Echochrome (From http://pcprofessionale.it)
Shift (PC. Website: http://armorgames.com/play/751/shift) is a 2D platformer in Flash that
tinkers with how people perceive space and negative space. The game is presented in black and
white, and when the character is in black (white), he can move in white (black) areas. (Games
with similar ideas: Monoverse)

Figure 2.4 Shift (From http://slidetoplay.com)

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The Unfinished Swan (PC. Website: http://giantsparrow.com/games/swan/), the product of
a University of Southern California Interactive Media Division student Ian Dallas and a finalist in
the Independent Games Festival 2009, is a first-person painting game that lets players explore a
world in pure white by splattering black ink around.

Figure 2.5 Unfinished Swan (From http://giantsparrow.com)
Miegakure (PC. Website: http://marctenbosch.com/miegakure/), a finalist of IGF2010, is a
game that deals with the mathematical concept of 4D space. If we consider 2D space to be a
slice of 3D space, then we can view 3D space as a slice of 4D space. It plays like a regular
three-dimensional platformer, but at the press of a button, one of the dimensions is exchanged
with the fourth dimension, allowing for four-dimensional movement.
Figure 2.6 Miegakure (From http://marctenbosch.com/miegakure/)

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2.2 Core Mechanics
In Eyez there are two core spatial mechanics: Screen-Wrapping and Screen-Locking.
2.2.1 Screen-wrapping
The definition of screen-wrapping is when an object goes off one edge of the screen, it will
re-enter the screen from the opposite edge. In this way, the space within the screen is still
consistent in a sense, but is now in what is referred to as a “looping” mode.
Figure 2.7 Illustration of screen-wrapping in Pac-Man
In Eyez, there are three screen modes: Normal Mode, Blue-Eye Mode (Screen-wrapping
Mode) and Red-Eye Mode (Screen-locking Mode, which will be discussed later). In Normal Mode,
the camera will keep following the protagonist Mint and none of the spatial mechanics are in
effect. When the Blue-Eye Mode is triggered on, the camera stops following Mint and the
screen-wrapping mechanics becomes active, so Mint can “traverse” through the opposite edges
of the screen. Note that screen-wrapping also applies to some other objects such as projectiles.
Detailed description is provided in Section 4.
2.2.2 Screen-locking
Screen-locking on the other hand, is where the edges of the screen prevent objects from
going through, so things inside the screen cannot go outside and vice versa. In this case, the
on-screen space and the off-screen space are actually separated.

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Figure 2.8 Illustration of screen-locking in Breakout
Very similar to the Blue-Eye Mode, when the Red-Eye Mode is triggered on, the camera
becomes static and the screen-locking mechanic starts working, so Mint can use the hard edges
of the screen to protect herself from harmful objects such as spike and enemy, or perform
wall-jump to reach higher places. Screen-locking can also bounce projectiles back, which can be
used in various puzzles. Detailed description is provided in Section 4.
2.3 Story
The Western Alliance for Knowledge and Energy, more commonly referred to as W.A.K.E,
is a global experimental technologies cooperation focused on renewable resources to fuel the
world's largest manufacturers. Much of their recent success comes from a secretive division that
runs a corporate espionage unit augmented by their reality-blending technology: Eyez.
Our protagonist Mint is the only one given two opposite Eyez implants – the Red Eye and
the Blue Eye, which allow her to move through and manipulate her environment to sabotage and
steal from the company's competitors. These implants prove excessively unstable, slowly driving
Mint mad. During one of her missions, the devices fail her catastrophically, causing her to be
incapacitated and taken into custody by W.A.K.E.
In her coma state, Mint must navigate her own psyche, repair the damage caused by the
Eyez implants, and re-emerge into wakefulness. Once awake, she must evade other W.A.K.E
agents and escape from the W.A.K.E. facility.

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2.4 Control Scheme
The control of this game is based on touch-screen gestures, so there will not be a virtual
joystick feature that is commonly used in many mobile phone games.
2.4.1 Walking
Touch the screen with one finger and drag slightly left/right to the left/right without lifting the
finger to make Mint move to the left/right. Lift the finger to make her stop moving horizontally. This
input applies when Mint is either on the ground or in the air.
Notice that you don’t have to drag right on Mint to make her walk. Also you don’t have to
drag a long distance. Just dragging slightly will do the trick.
Figure 2.9 Control for Walking
2.4.2 Jumping
Touch the screen with one finger and flick upward quickly to perform a jump. The height of
a jump will be decided by the length of the trail. Flicking upward and diagonally will make Mint
jump forward. You can control Mint’s horizontal movement in the air by dragging left or right. Tap
the screen when Mint is jumping forward to cancel her horizontal movement.

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Figure 2.10 Control for Jumping
2.4.3 Triggering the Eyez ability
Double-tap the screen to trigger on/off Mint’s Eyez ability, i.e. switch the screen space
between the Eyez Modes (Blue-Eye Mode or Red-Eye Mode) and the Normal Mode. In the Eyez
Modes the camera freezes, allowing Mint to perform actions such as traversing between opposite
edges of the screen or wall-jumping utilizing the hard edges of the screen.
Figure 2.11 Traversing and Wall-jumping

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3 Core Game Objectives
The way space gets represented and implicated in videogames is no doubt strongly
influenced and shaped by other visual arts, such as painting, television and film. However, with
the new element of user interaction and the fact that the worlds in videogames are actively
created by programming (instead of being based on footage shot in the real world by cameras),
there can be more possibilities for user experience in videogames than in other forms of visual
arts. Professor Mark J.P . Wolf has discussed about this issue: “The use of space – on-screen and
off – in video games is certainly linked to cinematic space, which was an important influence on
its development. However, through combinations of the spatial structures mentioned above
(referring to the taxonomy written in the article), video game space goes beyond cinematic space
and shows the various possibilities for organizing space within a diegetic world, as well as
broadening the sense of what a diegetic world can be.” (Wolf 22)
The concept of Eyez was inspired by existing spatial structures in classical videogames.
The core mechanics of screen-wrapping and screen-locking in Eyez can be found in early
videogames like Pac-Man and Breakout. These two spatial structures were first introduced to
deal with memory shortage, and have existed for so long that they don’t seem strange to many
game players. When I began to think of the spatial structures themselves, I found I was obsessed
by the fact that they actually changed how players construct the game space in their minds and
how they think and move in that space, which affects their gaming experience.
My goal with Eyez is to create new and satisfying user experiences in game space other
than just simply transferring existing “authentic” experiences from physical space into game
space. By simply adding the screen-wrapping and screen-locking mechanics, players are given
the ability in the game world to perform actions that can’t be done in the physical world. In this
way, a 2D platformer game can offer a totally different gaming experience from its peers.

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4 Story and User Experience Description
The XNA version of Eyez was divided into 4 chapters, with each chapter representing one
stage of the learning curve for the players.
4.1 The Forgotten Garden
4.1.1 Story
Mint opens her eyes in a strange, sun-washed world of overgrown greenery and crumbling
ruins. Her surroundings are peaceful, quiet, and safe. There is something even familiar about this
walled garden, but that familiarity is unnerving, as though she is seeing her childhood house
run-down and empty. If this were some image from her past, she wouldn't know it, as Mint
remembers nothing but her name.
Quickly, Mint realizes that she is trapped in this sanctuary. Her only escape is in the
mysterious power of the Blue Eye. With the ability to wrap space itself, she navigates walls and
strange statues to reach the garden gate and freedom where snow blows through the door on a
harsh wind and the sky grows cool and dark.
4.1.2 User Experience
Upon starting the game, a new player needs first to get familiar with the control scheme:
drag horizontally to walk and flick upward to jump. At this moment, the screen space is in the
Normal Mode, which means the camera will keep following Mint and none of the spatial
mechanics are in effect. The player then needs to control Mint to go to the exit of the first level. To
find the exit and reach it is basically the goal for each level.

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After a few running and jumping exercises, the player is required to deal with a seeming
dilemma: he/she needs to go over a wall by entering the Blue-Eye Mode. In Blue-Eye Mode, the
camera becomes static and the screen-wrapping mechanics becomes active, so the player can
“traverse” through the opposite edges of the screen.
The player then needs to solve several puzzles involving buttons and doors. “Push the
button(s) and the door will open”—is one basic pattern for many of puzzles in Eyez. This
description might sound simple, but there can be different variations of these “button-door” types
of puzzles involving the Blue-Eye Mode. Pushing multiple buttons within a certain time limit to
open the door or pushing multiple buttons in a certain order to open the door are examples of this
method.
Near the end of this chapter, a new element, a statue, will be introduced to the player. The
player can move the camera onto the statue, which will reveal a certain part of the level on the
screen enabling the player to use the Blue-Eye Mode to solve puzzles.
Figure 4.1 Using a Statue to Perform Traversing
4.2 The Lonely Peak
4.2.1 Story
Mint leaves the comforting glow of the confining garden, and steps into a dim, winter night.
After traversing the barren foothills of a snowy crag, she sees a hooded figure at the edge of her
vision. She hardly has time to acknowledge the company before the stranger runs away. Looking
for answers, Mint gives chase up the mountain. The hooded figure calls for Mint to remember her

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past, triggering the Red-Eye ability which Mint can use to protect herself as she climbs. Blurry
pieces of her past identity are catching up with Mint as she gains on the stranger.
At last, they reach the top of the mountain, near the edge of a dark, shadowy fortress.
Before the stranger can give Mint any real answers, the stranger is dragged back into the fortress
by menacing, monstrous guards.
4.2.2 User Experience
The player is introduced to the Red-Eye Mode at the beginning of this chapter. In Red-Eye
Mode, the camera becomes static and the screen-locking mechanics gets triggered on. The
player then learns to wall-jump in the Red-Eye Mode, which helps Mint go to higher places. Note
that levels in this chapter are less open than those in Chapter One, so the Blue-Eye Mode won’t
always work.
The new elements of spike and turret are then introduced to the player, and the player
needs to advance the game facing these two harmful factors. If Mint touches a spike block, she
will die and the level will be restarted. Turrets shoot out projectiles and if Mint gets hit by a
projectile, she will be hurt and the camera will be zoomed in to a certain scale. After a few
seconds Mint will recover and the camera will be zoomed out. However, if Mint gets hit by
another projectile when the camera is zoomed in, she will die and the level will be restarted. Note
that the camera zoom-in is actually a very important technique the player needs to master, as
there are puzzles that can only be solved utilizing this technique.
Figure 4.2 How Projectiles Move in Blue-Eye Mode and Red-Eye Mode

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Later in this chapter, the player learns that projectiles shot out by turrets also comply with
the spatial rules of the Blue-Eye Mode and the Red-Eye Mode. To be specific, in Blue-Eye Mode,
when a projectile goes off one edge of the screen, it will re-enter the screen from the opposite
edge; in Red-Eye Mode, when a projectile hits an edge of the screen, it will bounce back (no
matter if it’s on-screen or off-screen). This trick can be used to push buttons and open doors in
various puzzles.
4.3 The Prison of the Past
4.3.1 Story
Mint explores the fortress, searching for the captive stranger in this ominous prison.
Nightmarish guards patrol the halls and traps wait for one misguided step. This fortress demands
the use of both her Eyez powers in balance to progress.
These dangers and trials are juxtaposed against comforting language. “We are only trying
to protect you, Mint.” “This is for your own good, you'll see.” “The company is a family.” “We won't
let you hurt yourself.”
After some time wandering the corridors of this labyrinthine structure, Mint finally finds and
opens the door to the hooded stranger's cell. She finds the stranger lying in a pool of blood. As
Mint approaches, the hooded stranger changes form, becoming Mint herself.
The unknown voice comforts Mint, telling her that they tried to protect her, but her abilities
proved unstable. It continues to say that though Mint became an unreliable operative, she would
always be kept safe by the company–that they will use her to learn from their mistakes. The
words are almost kind, and perhaps some of them are correct. Perhaps it was her fault that all of
this has happened. Perhaps the company was truly trying to keep her safe.
Mint rebels against this idea, trying to recall what happened. When she finally does, the
voice warns her: “You have nowhere else to go.” The dark prison disappears in a flood of light.
Mint wakes up.

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4.3.2 User Experience
Viewing the previous two chapters like tutorials, this chapter can be a little more serious.
Puzzles in this chapter are more comprehensive and complicated. In order to go on, the player
needs to master the concepts and skills he/she learned in the previous chapters. Besides, two
new elements are implemented in this chapter.
The first one is Eyez Points (EP). EP is the resource for using Mint’s special abilities.
When the camera is in Blue-Eye Mode or Red-Eye Mode, EP will keep decreasing. While in
Normal Mode and when Mint is standing on the ground, EP will keep increasing until full. When
EP is reduced to 0, the camera will go back to Normal Mode. In this case Mint can’t use her
abilities before EP is fully recharged. With this time-limit restriction, even a simple puzzle will
become more challenging to the player.
The other is the enemy. The idea of having enemies is nothing new to common platformer
games, but the enemy in Eyez is something different. There is only one kind of enemy in this
chapter, which will just keep moving back and forth in a certain area. Just like the case with
projectiles, if Mint touches an enemy, she will get hurt and the camera will be zoomed in (and be
zoomed out after a few seconds). If Mint touches an enemy when the camera is zoomed in, she
will die and the level will be restarted. However, an enemy also has the same attribute of a statue,
which means that the player can move the camera onto a moving enemy and enter the Blue-Eye
Mode or Red-Eye Mode at the right time.
4.4 The Waking World
4.4.1 Story
Mint wakes in the bright light of a medical wing. Most of her memories have returned to her
while she was dreaming, but some details remain hazy. It is clear she has been under sedation
for some time and that the company she worked for is keeping her without her consent. Is it for
her protection? Is it for theirs? Mint still struggles to understand as she stands. As soon as she

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pulls herself away from her hospital bed, alarms begin to sound. There is no more time for
questioning herself. She has to run.
Mint races through the halls of the real world, dodging hospital technicians and security.
This is the fastest paced of all the environments so far, demanding that Mint not only work quickly
but also utilize all the abilities she has learned so far.
When at last she passes through the doors to the outside, the voice repeats the warning
from her dream: “You have nowhere else to go.”
4.4.2 User Experience
This is the climax part of the game, a “challenge mode” for the player.
In this chapter, many puzzles require the player to perform input coherently, because if the
player doesn’t, either Mint will die or there will not be enough time left. This requires the player to
think ahead in order to perform actions more accurately.

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5 Development Process
The development process of Eyez went through two stages. The first stage of the
development was based on the Torque2D Game Engine, and the second stage was on
Microsoft’s XNA Game Studio.
5.1 Digital Prototyping using Torque2D Game Engine
The first digital prototype of Eyez was made in April 2009 using the Torque2D game
engine. Since it was an experimental prototype mainly focused on game mechanics, I didn’t
spend much time on the story side, which left the story slightly ambiguous requiring several
modifications in later builds.

Figure 5.1 Screenshot of the Torque2D prototype of Eyez
I resumed this project in September 2009, and with the help of two friends I made twelve
builds within two months and submitted the game to the Independent Games Festival 2010

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(IGF2010). The Torque2D version of Eyez consists of six levels, each level focusing on one
aspect of the core mechanic. I did all the design, art and coding work, and had two friends help
with sound design, proofreading and playtesting. Though it didn’t make it to the IGF finals, I did
get some really promising feedback from the IGF judges, who encouraged me to continue on this
project.
5.2 Development using XNA Game Studio
In May 2010, after I decided to make Eyez my thesis project, I started the development of
the new prototype using Microsoft’s XNA Game Studio and chose the upcoming Windows Phone
7 (WP7) to be the target platform. There were several reasons behind this decision. First, I’ve
always wanted to learn more about programming, and XNA had been on my to-do list for a while.
Second, XNA4.0 supports WP7 game development, and it’s much easier to publish a game and
let people play it on a mobile platform like WP7 (especially when its online marketplace is not yet
overwhelmed by over 250,000 applications). Third, developing games on a mobile platform using
a more programming-centric tool like XNA (instead of common game engines like Unity3D or
Torque2D) is a big challenge to someone like me who doesn’t have a computer science
background, –and I like challenges.
The most important change in the XNA version of Eyez is that it has become a platformer
which features a side camera view instead of the top-down camera view as was the case in the
Torque2D version. This simple but fundamental change brings in the factor of “gravity” – or what
we perceive as gravity (because it is just a math simulation applied on certain 2D sprites). With
this new factor, there can be more interesting variations on the gameplay.

20
Figure 5.2 3-view of the protagonist Mint in the WP7 version of Eyez
Another substantial change is the control scheme. The Torque2D version of Eyez featured
a traditional keyboard and joystick input. However, on the WP7 platform you can only perform
input using touch-screen and accelerometer (or maybe some not-so-common input methods
such as microphone and GPS). There are many touch-screen games that feature virtual joystick
control scheme, but virtual joystick controlling just didn’t appeal to me. The touch-screen
interface is totally different from traditional button-based input devices, and simply copying the
control schemes with a joystick onto a touch-screen based platform did not seem like the best
solution to the problem. If I was going to develop Eyez on WP7, I needed to design an accessible,
user-friendly control scheme. I then spent a lot of time researching existing touch-screen based
mobile games, and with inspiration from great examples like Mirror’s Edge (iOS) I finally
designed the control scheme for the new Eyez. From all the playtesting thus far, I can tell that this
control scheme does have potential, though it still needs some fine-tuning to maximize its
usability.
There are also many other changes I made in the XNA version to address concerns from
the older PC version. In terms of game design, I simplified the core mechanics in many ways. For

21
example, in the Torque2D version the camera would zoom in or zoom out when in the Blue-Eye
Mode or Red-Eye Mode (i.e. Eyez Modes). This made the game design process more difficult,
and playtesters complained that some puzzles seemed “glitchy”. In the XNA version, the camera
will not zoom in and out when in Eyez Modes. Even when the camera zooms under certain
circumstances, the screen-wrapping and screen-locking mechanics won’t be triggered during the
zooming process. These simplifications made the user experience smoother and more satisfying.
Figure 5.3 Screenshot of the WP7 version of Eyez (WIP)

22
6 Playtesting and Evaluation
In playtesting Eyez, I looked closely at how players solved the puzzles utilizing the core
mechanics to further support the concept of this project. If, upon getting familiar with how the
spatial logic works in this game, players figured out the puzzles by themselves and enjoyed the
gaming experiences, I would know this game system, based on my belief about manipulating
players’ spatial perception in videogames to provide unique gaming experiences, was working.
Early user feedback about the Torque2D prototype proved my concept to be successful.
There were in all six participants in the early playtesting of the Torque2D prototype and five of
them have given me written feedback. All of the playtesters were my teachers and friends, and
most of them were male at age 20-30. Though the playtesters suggested various improvements
on different aspects of the game, such as adding a hint system, adjusting the time limit for
buttons to reset or getting rid of the inertia in the character movement, all of them commented
positively on the spatial mechanics. One playtester was having some difficulty with the
screen-wrapping mechanics at the beginning, but when he finally figured out what was going on,
he couldn’t stop playing and enjoyed the game. After the playtest, he admitted that the idea was
mind-blowing and he was really enjoying doing those “impossible” things inside the game.
Submission to IGF 2010 was also a very important playtest for Eyez. Almost all the judges
who played the Torque2D version of Eyez said they liked the concept, and many of them
encouraged me to do better on the execution and make it into a great game in the future. Here
are some feedbacks from the judges:
 “Great concept, but rather average execution. Let down by the art, music was plain, and
checkpoints are rather awkward. …A very interesting base idea, hope it can be turned
into a great game in the future.”

23
 “I like the core idea of the game. Ramping is one issue you should work on. You start
the player out with a new idea, and then ramp it too quickly, and don't let it brew.”
 “Really like the concept of this one, although it could do with a more intricate world and
the story integration didn't quite work for me. The spatial gimmick works really well, and
the music sets a great atmosphere.”
From this feedback, the most important thing I learned was that I need to make the
ramping of the learning curve much smoother in order to offer a better user experience.
Playtesting of the XNA version further supported my belief. Combining the new element of
“gravity”, a lot of new possibilities were brought to the game design and the user experience.
After trying the first prototype of the XNA version, a playtester who played the Torque2D version
of Eyez said it was much better as a platformer.
From the playtesting result of Eyez, I can tell that changing the notion of space for some
people can be difficult. For instance, some playtesters told me they understood the rule of the
Blue-Eye Mode, but during playtesting the game they often got themselves confused by
performing wrong movements such as traversing into walls. However, it was usually these people
that couldn’t stop playing once they truly comprehended the simple spatial rules set in the game.
Figure 6.1 People playing Eyez on WP7 devices during the Winter Show 2010

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7 Discussion
7.1 Interesting findings about videogame space
I am from a background of Architecture Design, and my experience and knowledge of
architecture helped me a lot in my research about spatial perception in videogames. To me, the
knowledge that architects can perceive buildings out of blueprints is very similar to the instance
where videogame players can perceive space out of 2D images displayed on the screen. They
are all based on the fact that we humans construct what we see in our minds, just like Professor.
Donald D. Hoffman said: “Everything you experience by sight is your construction. This is, as we
shall see, more than brute fact; it is a dictate of logic.” (Hoffman 10)
From my research and experience in this topic, I found out some intriguing facts that might
be interesting to game designers who want to explore the potential of videogame space.
7.1.1 Avatar, and the sense of size and scale
In the physical world, we tend to get the sense of size and scale of a space based on the
size of our bodies, which is common sense to architects. A room about 2.8 meters (9.18 feet)
high is the right size for most people, but will feel definitely too small for people like NBA player
Yao Ming who is 2.29 meters (7.51 feet) tall. The narrow space under a table or a bed can
become a perfect dungeon for a little child, but definitely not for grown-ups.
In the videogame space, it’s different. Since players can’t be inside the screen, we tend to
get our sense of size and scale based on the size of our avatars – that is, if there are avatars in
the game you play. Recall any games you played so far that have avatars in them, and you’ll
notice that this rule almost always works. This is the case with Eyez. In Eyez the camera will
zoom in and out, and thus the size of the environment on the screen will change accordingly. So

25
how do the players know that the environment doesn’t actually grow bigger or smaller? The
answer is that the avatar of the player (in this case, Mint) also changes in size, and the relative
size of the avatar to the environment stays the same.
Note that in certain games that do not have an avatar, such as many “Escape the Room”
games, players can still figure out the sense of size and scale. A table should be about 30 inches
tall, and a screwdriver should fit in a hand… We get all of this information based on our
understanding of the physical world.
At the same time we also need to realize that in the videogame worlds, our common sense
of size and scale about the physical world doesn’t always make sense. In the world map of Final
Fantasy VIII, a city is about the size of your avatar’s size; and when you enter a small shop in a
town, it suddenly expands to a much larger room. This type of phenomena doesn’t go along with
our existing knowledge of the real world.
7.1.2 Spatial consistency, loading, navigation and maps
One great thing about videogames in contrast to traditional media such as film and
television is that players can navigate through the space in them. Based on our common sense
about the physical world, we tend to believe that the videogame space is as consistent as is that
of the real world. When we open a door in Resident Evil, we think we arrive in another room
connected by the door. And when we jump off a cliff in Monster Hunter Tri, we believe that we fall
into the canyon below it.
This assumption of spatial consistency is taken for granted by many game players.
Unfortunately, due to the hardware and software limitation, the representations of large-scale
game space have to be separated into multiple sections, with one section being loaded and
rendered at a time. In order to help players navigate through these segments of space with a
sense of spatial consistency, maps become important tools which help construct the desired
model (mapping) of the space in players’ minds.
Since navigation in space is a complex topic, I don’t want to dig too deep into it here.
However, I do want to point out that there is a lot game designers can do about the fact that the

26
players’ sense of spatial consistency is constructed based on the mapping of separate segments
of game space. By manipulating the mapping, we can also manipulate how players perceive the
“consistent” space in videogames.
The potential of spatial consistency in game can also be explored without the loading of
different segments of game space. For example, the Blue-Eye Mode and the Red-Eye Mode in
Eyez actually changed how players think of the consistency of the game space: in the Blue-Eye
Mode the space can still be considered consistent as in a “looping” mode, and in the Red-Eye
Mode the on-screen space is inconsistent with the off-screen space.
7.1.3 Cognitive Illusions
Cognitive illusions are the visual illusions where the eye and brain make unconscious
inferences. Research has shown that the reason for cognitive illusions can be the misapplication
of existing knowledge to the information of retinal images. Psychologist Richard Gregory wrote in
his journal Knowledge in Perception and Illusion: “Errors of perception (phenomena of illusions)
can be due to knowledge being inappropriate or being misapplied. …Following Von Helmholtz’s
lead we may say that knowledge is necessary for vision because retinal images are inherently
ambiguous (for example for size, shape and distance of objects).” (Gregory 1121)
In history, artists have worked with cognitive illusions. Some famous art pieces include
Rubin Vase by Edgar Rubin and Penrose Stairs by Lionel Penrose. There have also been
videogames that played with cognitive illusions, such as Shift and Echochrome, which can be
considered the videogame versions of Rubin Vase and Penrose Stairs.
There are now at least over fifty kinds of cognitive illusions (Changizi, Hsieh, Nijhawan,
Kanai, and Shimojo 459) known to the world, and I am sure it is a valuable resource of inspiration
for game designers.
7.1.4 Tinkering with Spatial Rules
Sometimes a minor change in the spatial rules in a game can make dramatic changes in
the gaming experience.

27
Teleportation is a familiar idea that appears in many classical videogames. Portal was the
first game that made teleportation a major spatial rule in the game world and developed many
interesting puzzles around that rule. The result was that its unique gaming experience earned it a
lot of critical acclaims from major game media.
Another great example is Super Mario Galaxy. Its charming gameplay was mainly
developed around its unique sense of “gravity”, which was unlike that of any other game before.
Eyez also falls within this genre. The core mechanics of screen-wrapping and
screen-locking actually added another layer of spatial context, thus leading the player to think
and act based on the spatial rules set in the game.
7.1.5 Spatial Perception based on the Screen
Today, most videogames are using the screen as their display device. In this way, the
screen is the only “portal” that links the physical world and the game world. At any moment,
players can only visually perceive the videogame world based on the space displayed on the
screen, i.e. the on-screen space. So how the on-screen space and off-screen space get
presented and implicated affects the players’ perception of the videogame world.
Professor Mark J.P. Wolf has already discussed the difference of on-screen space and
off-screen space between videogames and film: “Just as cinematic off-screen space differed from
theatrical off-stage space that preceded it (for example, characters could walk off-screen into the
space behind the camera), the off-screen space of the video game differs from that of film. First,
unlike film, off-screen space in a video game does not have a pro-filmic referent the way a filmed
space often does. … In a video game, not only the representation of space, but its very
implication, depend on being programmed and actively created. Second, because the video
game has no default structure for its off-screen space, that space can be shaped and structured
in new ways that did not develop in film or television. And finally, the video game, as an
interactive medium, often gives the player some control over the point of view, allowing one to
choose which spaces appear on-screen or off.” (Wolf 12)

28
Besides Professor Wolf’s discussion above, I also want to point out that there are some
differences between the spatial perception in the physical world and that in the videogame world
based on the screen. One interesting fact is in the perception of depth: although we can perceive
depth based on the 2D image displayed on the screen, the 2D image itself doesn’t have any
depth, so a lot of interesting things can happen in the videogame world based on this paradox.
For example, in some 2D platformer games such as Braid, the character can jump vertically
through a platform and then falls onto the platform, which can’t be explained using our common
sense in the physical world. There are also some games that intentionally utilize this paradox,
Fez being one of them. In Fez, the player can rotate the camera 90 degrees at a time, which lets
the player realize that the game world is a 3D world. However, when the camera is not rotating
there is no depth cue in the on-screen space, and the main character Fez can actually move in a
traditional 2D platformer way.
In Eyez I also explored the use of on-screen space and off-screen space as part of the
game mechanics. By moving and zooming the camera in the game, i.e. changing the proportion
of the on-screen space in the game world, the potential of screen-wrapping and screen-locking
can be maximized and thus offer interesting gameplay experience to players.
7.2 Next Steps
For now Eyez is a single-player game. Though a multi-player component was a part of the
initial design, it was not implemented due to several limitations. However, I am very interested in
seeing how the gameplay would evolve when multiple (2~4) players can play together in co-op or
versus mode. I believe a lot of interesting gaming experiences will take place when the spatial
rules in each player’s world collide with their fellow players’.

29
8 Conclusion
People previously created and experienced videogame space based on their knowledge
about the physical space. But videogame space can be so much more than the mere
representation of the physical space. This is because the space we perceive in videogames is
actually a model we construct in our minds based on the 2D imagery information we see on the
screen. By manipulating what people see on the screen, we can manipulate people’s spatial
perception in game and thus create experiences that can only be found in videogame space.
This fact leads to a change in the notion of how we should design the space in
videogames. Today videogame development costs have skyrocketed and the major part of the
costs have been used to create more photorealistic videogame worlds for players to explore.
However, a more expensive and “authentic” videogame world doesn’t necessarily offer a better
gaming experience for its players. It’s what the players would think and what they can do in the
videogame worlds that make the difference. And since there is so much we can potentially
achieve in offering unique experiences by manipulating players’ spatial perception, game
designers should focus more on “interaction” and “innovation” rather than mere “authenticity”.
Cultivating people’s spatial literacy is something we should keep in mind when creating
interactive experiences. In the near future, interactive entertainment and virtual community
service could be seamlessly blended into our physical world. So it is crucial that people know
what they can potentially do—such as navigate, get the sense of size and scale, understand
spatial functions, etc.—with these new elements in order to enjoy a better life in a physical world
mixed with a virtual world.
Finally I also want to point out that the idea of videogame space is being developed
without limitations to the space within the traditional monitor screen. Some recent trends in the

30
videogame industry have expanded (or are expanding) the boundary of what we define as
videogame space. For example, stereoscopic display gave people the ability to see depth out of
flat screen. Augmented reality technology blurred the boundary of physical space and virtual
space by mixing them together. And the implementation of GPS in games is changing the
physical world into a giant game map. … With these new changes going on, there will be more
potential for us to explore in videogame space, and we game developers can create more
meaningful and innovative user experiences for players.

31
Glossary
Avatar A computer user's representation of himself/herself or alter ego in the
form of a 2D sprite or 3D model used in videogames.
Escape the Room A subgenre of adventure game. The object of the game is to find a way to
escape from a mysterious room. The room usually consists of a locked
door, several objects to manipulate as well as hidden clues or secret
compartments. The player must use the objects to interact with other
items in the room to reveal a way to escape.
GPS Global Positioning System
IGF Independent Games Festival
Torque2D A game engine developed by GarageGames.
XNA A set of tools with a managed runtime environment provided by Microsoft
that facilitates computer game development and management.
Wrapping The process of limiting a position to an area in computer graphics.

32
Bibliography
Changizi, Mark A., Andrew Hsieh, Romi Nijhawan, Ryota Kanai, and Shinsuke Shimojo. "Perceiving
the Present and a Systematization of Illusions." Cognitive Science. 32 (2008): 459–503. Print.
Fermuller, Cornelia, LoongFah Cheong, and Yiannis Aloimonos. "Visual Space Distortion." Biological
Cybernetics. 77.5 (1997): 323-337. Print.
Gregory, Richard L. "Knowledge in Perception and Illusion." Phil. Trans. R. Soc. B. 352 (1997):
1121-1128. Print.
Hoffman, Donald D. Visual Intelligence: How We Create What We See. 1st ed. 1 vol. New York, NY:
W. W. Norton & Company, 2000. Print.
Wolf, Mark J.P. "Inventing Space: Toward a Taxonomy of On- and Off-Screen Space in Video
Games." Film Quarterly. 51.1 (1997): 11-23. Print.

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Asset Metadata

Creator Chen, Hua (author)

Core Title Eyez: Spatial perception in videogames

School School of Cinematic Arts

Degree Master of Fine Arts

Degree Program Interactive Media

Degree Conferral Date 2011-05

Publication Date 05/03/2011

Defense Date 03/25/2011

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,platformer,puzzle game,spatial cognition,spatial design,spatial perception,video game,visual perception,Windows phone,XNA

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Swain, Christopher (committee chair), Brinson, Peter (committee member), Hight, John (committee member), Swift, Kim (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c127-15577

Unique identifier UC1100766

Identifier usctheses-c127-15577 (legacy record id)

Legacy Identifier etd-Chen-4299

Dmrecord 15577

Document Type Thesis

Rights Chen, Hua

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu