CRSG: A Serious Game for Teaching Code Review
The application of code review in a development environment is
essential, but this skill is not taught very often in an educational
context despite its wide usage. To streamline the teaching pro-
cess of code review, we propose a browser based "Code Review
Serious Game" (CRSG) with high accessibility, progressive level
diculty and an evolvable foundation for prospective improve-
ments or changes. The application is built as a serious game to
reinforce the learning experience of its users by immersing them in
its story and theme, helping them learn while having fun. The eec-
tiveness of the game components are measured with a case study
of 132 students of 2 software engineering courses. The promis-
ing result of this case study suggests CRSG can indeed be used
eectively to teach code review. The demo video for the game can
be accessed at https://youtu.be/FLnr3p4bhOg, and CRSG itself at:
•Social and professional topics →Software engineering ed-
•Applied computing →Interactive learning envi-
code review, software engineering education, serious games, teach-
ing code review
ACM Reference Format:
Kaan Ünlü, Barış Ardıç, and Eray Tüzün. 2020. CRSG: A Serious Game for
Teaching Code Review. In Proceedings of the 28th ACM Joint European Soft-
ware Engineering Conference and Symposium on the Foundations of Software
Engineering (ESEC/FSE ’20), November 8–13, 2020, Virtual Event, USA. ACM,
New York, NY, USA, 5pages. https://doi.org/10.1145/3368089.3417932
The usefulness of proper code review is undeniable for increas-
ing code quality since it is centered around checking for code de-
]. However, despite its merit and popularity in the indus-
], it is hard to streamline this process since it has no denitive
guideline to adhere to (eg. what to look for while reviewing code
may change even among dierent organizations). Also, the teaching
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of code review in Computer Science curricula is not wide-spread [
As such, it is quite important to nd a way for teaching code review
in an accessible, streamlined and possibly customizable manner that
can be followed easily to work in a number of dierent scenarios.
The following are the scenarios where the teaching of code review
•Individual learning (e.g independent developers)
Professional learning (such as during orientation sessions
for new employees)
•Education (At schools, as early as coding is introduced)
We extended a browser based "Code Review Serious Game" (CSRG)
by Ardıç et al. [
]. Current version aims to teach its players the
concept of code review along with code review ethic and code
examples in the form of playable game levels to create working
experience on the subject while having fun as a way to address
this problem of teaching code review. Such a tool would potentially
have a user-base beyond what is mentioned above, eg. catering to
researchers who wish to conduct experiments about code review.
Another advantage of it would be its potential for extensibility; the
base game can be modied to t the standards of a certain company,
or be specialized for certain programming languages over others.
2 GAME DESIGN
This section consists of 3 main pieces. Subsection 2.1, Game Flow, is
a short description of the planned player experience, and the main
gameplay loop behind it. Subsection 2.2, Design Highlights and
Components, is a list of the more vital elements in the game (such as
the game levels), how they are structured, and why so. Subsection
2.3, Implementation Approach, deals with why certain front and
back-end methods have been used during the implementation of
2.1 Game Flow
The game has a tutorial, a practice level and 4 actual game levels.
The tutorial has a number of code segment examples where each
has a single defect in it, together with its classication, description,
reason, and how the author could x it. The practice level is like an
interactive manual that teaches the mechanics of the game to the
player. The game levels themselves are larger code segments with
numerous code defects planted in them. The player has to nd all
of them, along with their classications, to be able to complete the
2.2 Design Highlights and Components
This section explains the important components in the application
which either contribute to the teaching process or improve the user
experience while playing.
ESEC/FSE ’20, November 8–13, 2020, Virtual Event, USA Kaan Ünlü, Barış Ardıç, and Eray Tüzün
Story and Emotional Palee.
Creative director for the video
game Journey, Jenova Chen, during his 2013 GDC [
] talk mentions
the presence and importance of emotional palettes in creating a
product, and especially a game: An emotional palette refers to what
kind of audience a game attracts by giving what kind of emotions
to them. This could be a sense of achievement, empowerment,
socialization, relaxation etc.
Following Jenova Chen’s principles, an emotional palette is es-
tablished for the game. As learning code review (CR) without much
stress and having fun while learning it is the primary objective of
the game, a theme of exploration felt tting for it, and the serious
game is built around this concept.
To achieve this, Star Trek [
] was taken as an example. In most
episodes of the classic Star Trek series, some problem would occur,
but through science, bravery and kindness the crew would be able to
beat any hardships that came across their way, and learn more about
themselves and the galaxy that surrounded them. Remembering
this, with the famous catchphrase of the series: “Space: the nal
frontier. These are the voyages of the starship Enterprise. Its ve-
year mission: to explore strange new worlds. To seek out new life
and new civilizations. To boldly go where no one has gone before!”,
it was decided that the exploration theme would take a turn for
“space exploration”, and a protagonist that would have to help x
their way through their problems using the subject of the game,
CR, to explore space, where no one had gone before.
Stella is an eort at the gamication of this serious game
beyond visual and auditory eects, to pull the players into the de-
signed theme with interactivity to possibly help them experience
the content in a ow state as per Csikszentmihalyi’s denition [
a personality the player can interact with. This personality can be
used by the player as if navigating a dialogue screen often seen
in popular Role Playing Games (such as Pokémon [
], or Fire Em-
]) to both learn tidbits about code review ethic and also
to get tips about the mechanics of the game and a narration of its
Figure 1: A game level with the Stella modal zoomed onto.
This dialogue panel is made so that it automatically appears when
the main menu/level map is opened for the rst time or a game
level is opened at any time. The panel (ocially called a modal) can
be closed/disabled at-will by clicking outside of it. Clicking on the
modal instead will advance Stella’s dialogue. At any time during
the game in any level or in the level map, the player can click the
“log” button on the screen to re-access the modal in case they have
accidentally missed it, or wish to re-read some or all of it.
In the narration of the game, Stella calls this dialogue modal her
“log”, quite similar to the captain’s log seen in series such as Star
Trek, and uses it to describe her journey, and explain the notes she
has taken on CR in the form of CR ethic/group-work advice.
In its creation, attention is given to ease of understanding and
use: To keep the UI decluttered, there’s no exit button for Stella’s
log, but the cursor changes shape to a “?” inside the modal, and
a pointing hand outside of it. The use of these two nonstandard
cursors suggest that clicking in and outside have dierent functions
(as described earlier). The modals include the portrait of Stella
in a few variations, to give the log some character in addition to
its functionality; it shakes and stutters as if viewed from a cheap
camera/screen. One other visual feature of the log is the text in
it. It is made in a way that going to the next entry will make the
modal write with a typewriter animation (so, owing letter by letter
quickly) and give out a keyboard sound, to give the feel that this
is Stella writing in her log. It is expected for this addition to be
eective in pulling the player into the game’s theme.
The CR ethic tips that come from Stella are a blend of the tips
that come from Thoughtbot’s Guides  and our experiences.
In explaining how crowd-sourcing in the
form of a game allowed the 2009 “oating duck island” asco to
be fully uncovered in a very short time, Jane McGonigal draws
attention to mankind’s attraction to reactivity: “The game interface
made it easy to take action and see your impact right away. When
you examined a document, you had a panel of bright, shiny buttons
to press depending on what you’d found.” [
]. Keeping this in
mind, it would make sense to make intended player interactions
more visually appealing and convenient to use than the rest of the
screen and keep a record of the player’s achievements, such as their
scores in a leaderboard, to better keep them invested with the game.
Visual responsiveness is aimed for in the creation of CRSG.
some of this responsiveness, largely due to its instability in regard
to zoom levels across dierent computers and browsers. However,
the game still has a number of responsive elements that provide the
player with feedback about their progress in the game: The player
can ask for hints in any level, and a pop-up will come up from the
bottom of the page telling them a single hint specic to that level;
clicking the hint button again will cause a dierent hint to pop up.
When the player submits their answers in a level, their answers are
lit up in green (the answer is correct), yellow (the correct lines are
marked but the stated defect type is incorrect) and red (the answer
To further emphasize the emotional palette
of the game, the UI of the game is made so that it looks like the
player controlling Stella’s journey through space. Utmost attention
is given to the construction of these UI components to be neither
barren, nor overwhelming, providing enough information clearly
while not being too busy .
Refer to Figure 2 as the components are explained below.
Level numbers and descriptions do not pop-up as tooltips that
can be missed, but are instead given under or over space stations
in white font without any background. This way, individual levels
and what they mean are instantly revealed and are easy to read,
but the text does not detract from the appearance of the map, nor
does the UI feel too cluttered.
Each space station has a gap in their middle where the button
for the corresponding level resides. This space is made part of the
CRSG: A Serious Game for Teaching Code Review ESEC/FSE ’20, November 8–13, 2020, Virtual Event, USA
Figure 2: The level selection screen of the game.
theme by making them travel relays: Relays Stella has to help repair
using CR to be able to travel to the next station/level. To indicate the
hardness of the level the player wishes to go into, each successive
relay is shaped like a polygon of increasing number of vertices (The
tutorial has 3 vertices, the practice level has 4, 1st level has 5 etc).
Also, the mouse cursor is changed into Stella’s spaceship, the Crane,
to add further into the atmosphere.
There’s music controller on the bottom of the screen, which
auto-plays music to increase immersion, but can be stopped, or its
sound level adjusted at-will.
The tutorial is made to ameliorate the steep learning
curve of CR that comes from the lack of its formality by teaching the
players via denitions and examples with solutions. In its current
version, it houses 10 dierent code segments, each with a distinctly
dierent code defect in it. The player can read the denition on
any example to see what the type of the defect is alongside that
type’s explanation. To make the learning experience smoother, for
those who learn better with shapes, the two main defect classes,
evolvability and functional defects, are denoted on the tutorial
screen with the shape of a brain and a wrench respectively in
addition to the text. For those who learn better with colour, dierent
defect sets have unique colours to them.
Figure 3: The tutorial of the game after seeing the defect and
its explanation in an example.
The player can click the “show the solution” button to see the
solution of the shown example defect. When they do, they then see
the “see the defect” button. This button reverses the shown solution
back to its original way so that the player can compare the defect
and the solution at their own pace without having to reload the
page and come to the defect they were looking at each time. Also,
when the“ show the solution” button is clicked, the defect on that
example and how it can be avoided/xed is explained where the
denition of the defect type is given before seeing the solution.
There are four in-game helpers. These are
game components aiming to help smooth the learning experience of
the player like the tutorial, but without having them leave the level
they’re playing, unlike the tutorial. While they are not as descriptive
as the tutorial by themselves, they work well in tandem to explain
the player some aspects of CR they might not have understood
without needing to disrupt the gameplay.
Figure 4: The editor screen, where all levels are played.
Refer to Figure 4 of the editor screen above for the descriptions
of the in-game helpers. These 4 helpers are:
This is one of the tabs on the bottom left of the editor
screen. It houses the taxonomy tree of code defects, and concise
denitions for all defect types listed below it. These defect types
are coloured in the same way as they were in the tutorial to help
those that learn with colour better. Also, to help those with reading
and concentration problems, each defect type is separated from one
another by cells of alternating shades.
This is another one of the tabs on the bottom left
of the editor screen. It has in it a numbered list of items to check
while reviewing code. It is structured in a way that the reviewer
is encouraged to review the code starting from more easier to
see defects and move on to more contextual, harder to see (and
sometimes more situational to the used programming language)
ones. It is also structured in alternating cells like the guide to make
it more readable.
This is a button on the bottom left part of the ed-
itor screen. When clicked, the browser asks in a pop-up whether the
player really wishes to see the answers or not to prevent accidental
clicks, and if terminated armatively, shows the correct defects on
the top left part of the editor screen and switches the bottom left
tab to the description tab, changing its contents to the explanations
of the defects listed above. This way, the player not only sees the
correct defects, but also has a chance to read the reason behind
ESEC/FSE ’20, November 8–13, 2020, Virtual Event, USA Kaan Ünlü, Barış Ardıç, and Eray Tüzün
them. These explanations are also structured in alternating cells
like the guide to make its reading easier on the eyes.
This is an entire level, level 0 to be exact. It
describes through comments how the scoring, defect selecting,
submitting, seeing answers etc. are done via comments in the editor
to the right side of the editor screen. It also encourages the player
to try the defect selecting system out by explicitly pointing out
parts on the code segment to be selected. This part of the game is
integrated to the theme by giving it the avour of a CR machine’s
user manual Stella nds in her ship to help her in her journey.
Granted that they are following the instructions in this tutorial
level, the players have a great opportunity to familiarise themselves
with the various helpers on the editor page using this level.
2.3 Implementation Approach
The three main goals this game strives to provide its players/learners
are, as per the introduction, a streamlined learning process, high
accessibility, and an experience that can be tailored for dierent
standards. CRSG satises these constraints with its level design,
and browser based implementation. Below is how they manage to
satisfy these constraints, and how they aect the use of components
in the game, where relevant.
Level Design Philosophy.
The levels should become harder not
at once, but step by step, to allow the player to grow step by step
together with it, and not feel overwhelmed. In CRSG, similar to
how the checklist is structured, the levels are designed in a way that
they become progressively harder as levels progress: The earlier
levels are more likely to have more physically obvious defects
(such as bracket or indentation mistakes), while the later levels
are way more likely to be dominated by defects that require the
code and the language it was written (this was Java in our case) in
to be understood clearly to be found out and diagnosed (such as
algorithm/performance or memory management defects).
With such progression implemented into the game, the players
are expected to need only the rst half of the guide and checklist
in the earlier levels, and the rest of these components in the later
levels (conveniently so, since both of these components are ordered
roughly with this progression in mind), essentially splitting the
reading load they might have into more digestible chunks.
Web Based Development.
To satisfy the premise of accessibil-
ity, web based development is assumed for this game. This means
anyone who wishes to play the game and has the web address for
it can get on playing it without nearly any investment on their part
(such as payment for a physical copy, hard disk space for installa-
tion, steady and high-speed internet etc). This is because the game
runs directly on the client side and communicates with Google
Firebase  cloud service for authentication and data retention.
One downside of this approach is the limits of HTML/ CSS/
high level programming languages that are made for building games,
certain dynamic embellishments for the UI and user pipeline short-
cuts had to be cut from the nal version of the game, pushing the
development instead for a more minimalist design.
The use of frameworks have been avoided to make the evolv-
ability higher for developers that wish to edit the game for their
3 CASE STUDY AND EVALUATION
We have developed CRSG in order to be able to conduct CR related
lab sessions on a number of courses which either focus on technical
skills regarding programming, or soft skills and perspectives regard-
ing the industry. We conducted video conference based sessions for
Object Oriented Software Engineering and Application Lifecycle
Management courses consisting of 52 and 80 students respectively.
Moreover, we were able to conduct a survey after these sessions
where we asked the students to evaluate the usefulness and their
enjoyment of the game components on a 5 point Likert scale. Table
1 presents the averages for each component and overall enjoyment.
Stella’s lower usefulness score can be explained with her log lack-
ing substance that can be directly used in game (and instead having
real-life advice in it). It could possibly be improved by introducing
a mini-quiz into her log screen about code review.
Table 1: BY COMPONENT STUDENT EVALUATIONS
Component Average (1 to 5) Standard Deviation
Overall Enjoyment 3.64 0.89
Stella 2.43 1.03
Guide 3.52 1.13
Checklist 3.40 1.18
Tutorial 3.65 1.01
Practice Level 3.67 1.10
Answer Explanations 3.71 1.09
Hints 3.17 1.15
4 RELATED WORK
There are 2 major studies in the literature that are concerned with
teaching CR practices directly. Anukarna by Atal et al. [
] is a
decision making focused web based game which conveys the best
practices regarding the CR process by following a scenario which
demonstrates the required resources and outcomes of the process.
] developed a desktop game that presents a CR ow
in which the users play the role of the reviewer by nding defects
that are planted into a given code piece that is similar to our design.
However, the scope of this work is very limited since it misses
quality of life features like syntax highlighting or evaluation on
a large user base. To the best of our knowledge, neither of these
works are open source or available for public use.
5 CONCLUSIONS AND FUTURE WORK
In this paper, we have introduced CRSG, a serious game that aims
to teach code review related practices, and presented our design by
breaking down the game to its components since, our base design
is supported with many components that could help users learn on
their own. Such auxiliary components helped create a more com-
plete and useful gameplay experience. After the design, we discuss
how this game can be utilized as is or adapted while providing
results regarding our experiences with students in software engi-
neering courses. We aim to further improve CRSG by introducing
two other multiplayer game modes. One of which will incorporate
the role of the author into our game ow to better represent the
code review workows and another one to enable users to conduct
reviews as a group.
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