The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)

Study on Wiping Operation to Accelerate Human Activities on
Hidden Object Game
Tsetsegjargal Erdenebaatar(1)(Non-Member)

Tadahiro Fujimoto(1) (Member)

Kouichi Konno(1) (Member)
1) Graduate School of Science and Engineering, Iwate University
ekoshka89@gmail.com

fujitada@ iwate-u.ac.jp

konno21@iwate-u.ac.jp

Abstract
An aesthetical image composition and mysterious stories are the main components of a hidden object game(HOG) to make it enjoyable. In an HOG, players find objects hidden in an image and inquired by a list. As far as
we know, there have been insufficient studies to explore game elements such as the efficiency of game effects on
an HOG to accelerate human activities. In this paper, we propose “wiping operation” to accelerate human activities
for an HOG. In an HOG that we developed, first, an original image is transformed into a triangulated image. Then,
during game play, the quickness of the wiping action by a player makes the level of detail of the triangulation finerand rougher. We did an experiment to investigate the performance of the wiping operation. Each player in theexperiment wore a brain activity sensor to obtain a brain activity value during game play and answered aquestionnaire after game play. We show the experimental results by the questionnaire and brain activity value toverify the effectiveness of the wiping operation.

233

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)
been shown to be associated with user’s motivation and intentions for

1. Introduction

media use including various games [10]. Some suggested [11] app-

Hidden object games (HOG) are a subgenre [1, 2] of casual gaming.

based exercises are useful in impacting cognitive enhancements using

In HOG, a player must find objects that are hidden within a scene by a

the XB-01 brain activity sensor. Despite its low price and portability, it

given hint. The hint is often the names of the objects. The games have ais useful and reliable because of its robustness and efficiency [11]. Then

repetitive play, predictable storylines, enjoyments, etc. Aesthetical

our research introduces XB-01 as the brain activity sensor.

image composition and mysterious stories are used to make an HOG

An arbitrary image transformation's attractive appearance often

enjoyable. Therefore, exploring the efficiency of game effects on HOG

entertains the player visually. In some games, an object image is divided

is required to make an enjoyable HOG.

into tiles which are rearranged irregularly [12]. Typically, a target object

Measuring game enjoyment is a complicated task in the gameis blurred [13] or mosaicked [14], such as triangulation and quadrilateralresearch field. Some researchers correlated brain activity data anddivision. Triangulation is one of the typical image mosaic techniques,

questionnaire data [3, 4] to measure game enjoyment. Thus, using brain

one of the Non-Photorealistic (NPR) techniques. Jonathan [15]activity data by electroencephalographic(EEG) system proved todeveloped a system to triangulate an original image. In the digital

evaluate a game enjoyment. If player's brain is active, the gameartwork by Miguel Chevalier [16], triangulation is one of the typicalenjoyment is higher [3]. Then, if some human operation to acceleratemosaic effects with various polygonal pieces. Triangulation is a well-brain activity is able to introduce on HOG, it's operation becomes

known geometric technique used for multiple purposes such as image

effective operation to enjoy HOG.

processing, 2D/3D modeling, physical/mechanical simulation, andIn this paper, we propose a new wiping operation t on an HOG. The

graphic design. However, to accelerate human activity, triangulation

wiping operation is applied to a triangulated scene image in which a

HOG is not sufficiently evaluated.

player finds objects. This operation activates human brain and gives a

3. Proposed method

player great enjoyment. To verify the effectiveness of the wiping
operation, a brain sensor is used to measure a player’s brain activity.

To realize the wiping operation, we develop an HOG using a
triangulation algorithm [17, 18] on our game as follows:

2. Related works

1.

A hidden object game is a puzzle genre game in which players findAn original image is first transformed into an initial triangulated
image. As each triangle is large in the initial triangulated image, it

the objects from the list that are hidden within a picture. From the given

is difficult for a player to distinguish each object clearly.

English name of the list of objects, the player finds them. A hidden

2.

If a player moves hands over the triangulated image during

object game is usually used for learning a new language, such as English.

gameplay, the triangulation is refined in real time. Then, it

Playing the game to memorize a new vocabulary gave a significant

becomes easier to distinguish each object. We call this effect by

result in those researches [5, 6]. Therefore, acceleration of humanmoving hands wiping operation.

activities is necessary, since more effectiveness of HOG is required.

3.

In those games [1, 2], more minor effects are used to make their gameIf the player stops moving hands, the triangulation returns to theinitial state gradually.

enjoyable. For example, the silhouette of an object or randomly shuffled

4.

English words of an object make HOG more challenging. In another

After a certain period, the refined part returns to its initial state.
Then, it becomes harder to distinguish each object again.

way, the whole of a scene becomes black dark, and only an area on

5.

which a player moves a mouse becomes bright and visible. The player

The above 2 and 3 are repeated by the player’s hand movement
everywhere on the triangulated image.

has to find the objects while moving the mouse to see specific areas as

3.1 Wiping operation

if the player gives light to the areas the player wants to see.
Even though there are insufficient studies exploring game enjoyment

The wiping operation accelerates human activity on HOG. Thisin Hidden Object Games, Michael Sailer et al. [7] stated game design

operation refines the level of detail of a triangulated image by moving

elements address psychological needs and motivation even in non-hands over the image, that is, wiping the image as if to wipe a misted

gaming applications. At the same time, the benefits of developing awindow to see an outside scene clearer through the window. The

game based on player experience were indicated [8]. Therefore, torefinement is locally applied to only the image part, which a player

evaluate the game efficiency of human activity objectively, the Game

wiped. If a player moves hands over the image, triangles increase. Then,

Experience questionnaire [9] to measure new action on HOG is useful.

increased triangles decrease after a certain time. The demonstration of

New developments in Brain-Computer Interface (BCI) using

the game process is shown in section 3.2. In the increasing andwireless electroencephalographic (EEG) system provide recordings anddecreasing progresses, we use incremental and decremental

access to neuronal activity, enabling the computer to analyze

triangulation algorithms that reconstruct triangulation locally in efficient

information from brain waves. EEG data could be correlated to otherways.

physiological data measured during the experiment [3]. Enjoyment has
234

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)
real-time.

Triangulation
We used triangulation because of the low-cost as compared with othermethods such as the blur effect. In other words, when using a blur filter,
scaling the area takes more time than the Delaunay triangulation
algorithm.
After the game starts, a player first sees the initial triangulated image
generated by a Delaunay triangulation algorithm. The positions andkinds of existing objects are not recognizable in the initial triangulated

Figure 2: Local reconstruction of triangulation

image. During the game play, triangles are increased and decreased inreal-time. The color of each triangle of a triangulated image is given byMore points are added if the player moves hands faster. As a result,averaging the colors of the positions of the three vertex points on thethe player sees a more recognizable triangulated image. In other words,

original image. In Figure 1, (a) represents an original image, (c) shows

the triangulated image works as an approximation of the original image.

a triangulated image, and (b) shows the wireframe of the triangulated

The detail of the original image gradually emerges by the player’s hand

image.

motion, while the detail disappears after the lifetime of each point.
The triangulation is reconstructed repeatedly in real-time wheneverpoints are added and deleted during the gameplay. The initial points are
not deleted, which means that the initial triangulated image is recovered
after adding no points for a longer time, as shown in Figure 4. An
example of rough and fine triangulated images is shown in Figure 4. The
wireframes of (c) and (d) are shown in (a) and (b), respectively.

3.2 Our game
Our game story is simple. The rule of this game is to find 11 randomly
Figure 1:The triangulation of our game. (a) original image (b)placed fishes from the tank in 2 minutes. As we demonstrated in section

wireframe of triangulation (c) triangulated image after filled triangles

3.1, a player first sees the rougher triangulated image where the positions

The initial triangulated image is made using randomly generated

and kinds of objects are unrecognizable. When the player refines the

p=2000 points. In the image, the position where each object is locatedtriangulated image, the player can see where and what objects exist. The

is unknown.

finer and rougher changes in the level of detail of the triangulation are

If a player moves a hand, basically, 20 points are added in a hand

repeated by the wiping operation of the player during gameplay.

circle, whose center is the position of the hand, in each frame. For

Triangulation with fewer points looks rougher and makes objects more

example, if the updating rate is 30 frames per second, 600 points will be

unrecognizable. Therefore, a player needs to move hands more quickly

added per second. If a new point P(x,y) is added to the triangulation, as

to find objects fast. As shown in Figure 3, a finer triangulated image (c)shown in Figure 2(b), the triangulation is reconstructed locally, as shown

looks more recognizable than a rougher triangulated image (b).

in Figure 2(c). We used an incremental Delaunay triangulation
algorithm in this process. Particularly, the simple stochastic walkalgorithm [17] is used to obtain the location of the point in the(2)

triangulation. If the point already exists on the pixel coordinates (x,y)(1)

where a new point P(x,y) will be added, the new point is not added. In
this case, less than 20 points are added. If all pixel coordinates in a handcircle are occupied by the existing points, any new points are not added.
The added points have lifetime during which they remain. The added(1)

points are deleted after 0.3 seconds from the time when the points wereadded. In the deletion process, the triangulation is reconstructed using
the remaining points by the decremental Delaunay triangulation(2)algorithm, which makes the triangulated image unrecognizable again.
When the point P(x,y) is deleted, shown in Figure 2(c), from thetriangulation, the triangulation is reconstructed using local points aroundFigure 3: An example of rough and fine triangulated images. (a) An

the deleted point [18], as shown in Figure 2(a). The efficient local

original image. (b) A rough triangulated image. (c) A fine triangulated

reconstruction in adding and deleting points makes our game lively inimage.

235

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)

Figure4:
Triangulation
process. (a) wireframe of a roughtriangulated object (b) wireframeof a fine triangulated object (c) arough triangulated object (d) afine triangulated object.

is more than one target object to find, the objects are queried
one by one after each object has been found. (2) The time
indicator shows the remaining time to find target objects.
Limiting playtime excites the competitiveness of a player. The
player is usually given a task to find more than one target object
within a limited time. (3) The number of objects the player has
found is indicated.

4. Implementation
We developed our game in two environments: hand-gameand mouse-game. In hand-game, an image is projected on awall, and a player plays by moving hands in front of the wall.
The player's body movement is captured by a Kinect sensor, as
shown in Figure 5(a). In mouse-game, a player plays a game ona personal computer by holding a computer mouse, as shownin Figure 5(b).

(2)

(3)

(1)

Figure 5: Game environments (a) Hand-game (b) Mousegame

Figure 7: Interface of our game. (1) A target object to find.
(2) Time indicator. (3) Counter of found objects.

To measure brain activity, a player wears a headband with abrain sensor, XB-01 sensor, during game play, as shown in
Figure 6. We will describe it and compare both games’ results
in section 5.2.

4.2 Hand-game
The game screen is projected on the wall by a projector, as
shown in Figure 5(a). A player interacts with a game to findeach object, fish, by moving both hands in front of the projected
game screen.
First, if a player wants to find an object, fish, the player has
to refine the image to know where it exists. The player moves
hands on a specific image area where the object to find seems
to exist, which results in refining the triangulation of the area.
The Kinect sensor captures the hands' motion, andapproximately 20 points are added to each hand position as
described in Section 3.1. In the game screen, the positions of
the hands are represented by green circles, as shown in Figure
8. If the player wants to find an object, the player needs to movehands faster and not stop.
Second, if the player thinks that the object has been found ona certain position, the player grips a hand on the position as if

Figure 6: XB-01 brain sensor in a headband. A sensor must
be placed in the upper area of the left eye.

4.1 Interfaces of our gameThe main components of the interface of our game are shownin Figure 7. The components are the same in hand-game andmouse-game. They are as follows: (1) A current target object
to find is queried by showing its original image. Even if there
236

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)

to grab a real fish. The player can grip each hand.

remaining time. The local reconstruction of the triangulation by
wiping operation is replaced with the global reconstruction by
button press, and other game features are the same as thehand/mouse-games explained in sections 4.2 and 4.3. We callthe games explained in sections 4.2 and 4.3 hand/mouse-gameswith wiping operation, and the games explained in this section
hand/mouse-games without wiping operation.

(1)

5. Experiments(2)

We did an experiment to investigate the performance of our
new action, wiping operation, by showing how it accelerates
human activities on our hidden object game.
We did a survey for 26 players after playing the game.
Among them 16 players played the mouse-game while 10
players played the hand-game. 22 players were students aged
between 16 and 25, and 4 players were aged between 25 and36.

Figure 8: Interface of hand-game. Green circles (1) and (2)represent left and right hands respectively

4.3 Mouse-game
The game is playable by a mouse on a computer screen, as
shown in Figure 5(b). The green circle represents a mouseposition, as shown in Figure 9.
First, if a player cannot recognize the object to find, theplayer moves the green circle by moving the mouse over theimage area in which the object seems to exist. While the player
moves the green circle, approximately 20 points are added
around the green circle.
Secondly, if the player thinks the object has been found on acertain position, the player clicks the left button of the mouseon the position. If the object does not exist in the position, 5
seconds are reduced from the remaining time.

We asked the following questions to measure the player's
gaming skills. Table 1 shows that 22 players answered they playgames frequently: a month(7), a week(10), and daily(5).
Approximately 84% of the players have game enjoyment indaily life.
Table 1. Result of the Question “How frequently do you
play games?”
Frequency of playing game
PlayerDaily
5
Several times a week10
Several times a month7
Several times a year2
Not at all
2
Table 2 shows the players' desire for game playing. 21
players, that is, approximately 80% of the players like to playgames. This result implied the players have a taste of game tomeasure its enjoyment.

(1)

Table 2. Result of the Question “Do you like to play video
and/or computer games?”
Very
Somewhat
Not
Not
much
reallyat allPlayers
7
14
4
1

Figure 9: Interface of mouse-game. Green circle (1)represents a mouse position

The last question was asked to measure the player’s
experience in a hidden object game. Only 2 of the players had
never tried this type of game before.
Overall, the above results showed 26 players had any
experience in any type of game, which means they can value
game enjoyment.

4.4 Game without wiping operation
In order to evaluate wiping operation, we developed othertwo games for comparative experiments to the hand-game andmouse-game with wiping operation explained in sections 4.2
and 4.3. These games also use triangulated images generated
from an original image and reconstruct the triangulation.
However, the way of the reconstruction is completely different.
In these games, the game screen has a refine button. If a playerpresses the button, the triangulation is refined globally byadding new points randomly over the whole image. After
starting from an initial triangulated image, the player can press
the button anytime in the playtime and several times. Everybutton press adds new points and the triangulation is refined
gradually. One button press reduces 5 seconds from the

5.1 Questionnaire result
Enjoyment is a commonly stated reason why people playgames and why people are active. Therefore, we did a survey
using game experience questionnaire, GEQ [9], to measure theenjoyment.
Immediately after the game play, all players completed the
GEQ. The questionnaire has 7 factors: negative affect,
tension/annoyance, competence, challenge, sensory andimaginative immersion, flow, and positive affect. Each factor
consists of 2 questions and there are totally 14 questions as we
237

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)

Game factors

mentioned in Appendix. The questions measure the player’s
feeling statement by five-point scores ranging from 1 (notagreeing) to 5 (strongly agreeing).
Among 7 factors, “negative affect” and “tension/annoyance”
are negative questions. That is, lower scores mean better
evaluation. Other factors have positive questions, and higherscores mean better evaluation.
Figure 10 shows the questionnaire result of the mouse-game.
Each player played both of the mouse-games with and without
wiping operation. Then, the player filled in the questionnaire
for each game. In Figure 10, for each factor, the scores of allquestions of the factor for all players are averaged. As a whole,“negative affect” and “tension/annoyance” are given lowscores, which means that the games are given good evaluation.
Other factors are given high scores, which are higher than 3.
This also means good evaluation. After this, we consider 5factors other than “negative affect” and “tension/annoyance”.
The game with wiping operation is given higher scores than thegame without wiping operation for all factors. Especially,“competence” has larger difference, which is approximately
0.66, than as comparing other factors. The scores of“competence”, “sensory and imaginative immersion”, “flow”,
and “positive effect” are more than 4.

Negative affect

1.59
1.41

Tension/Annoyance

1.53
1.59
3.59

Challenge

3.81
3.66

Sensory and Imaginative
Immersion

4.63
4.38

Flow

4.50
4.44

Positive affect

4.69
4.59
1

2

3

4

Game Factors

2.15
2.55
2.15

Tension/Annoyance

3.65
3.4

Competence
Challenge

3.3

3.95

Sensory and Imaginative
Immersion

4.5
4.4

Flow

4.5
4.15

Positive affect

4.45
4.3
0

1

2

3

4

5

Score [1-strongly agreeing; 3-agree; 5-strongly agree]with a wiping operation

without a wiping operation

Figure 11: Questionnaire result of hand-gameComparing Figure 10 with Figure 11, the score of“tension/annoyance” in the hand-game is much higher than thatof the mouse-game. In the hand-game, players need to move
not only hands but also other body parts. We consider that someplayers felt tense. Besides, the hand-game uses a Kinect sensor
and it sometimes fails to capture a player’s hand motion exactly.
In such a case, we consider that the player felt annoyed. In
addition, the score of “competence” of the mouse-game wasmuch higher than that of the hand-game. The questions of“competence” ask the players whether they felt skillful andplayed the game successfully. Considering the play style of thehand-game by capturing the player’s hand motion using a
Kinect sensor, the hand-game must be difficult to playsuccessfully than the mouse-game which is controlled easily bya mouse.
To examine the game factor differences between the gamewithout wiping operation and with wiping operation, we
conducted the Wilcoxon signed rank test, which is a nonparametric statistical hypothesis test. Test results are shown in
Table 3. For the Wilcoxon test, a p-value is a test statistic
probability that implies a difference in the data distribution. If
the probability is below 0.05, it is indicated that there is asignificant difference in data.
Table 3 reveals a significant difference between the game withwiping operation and without wiping operation, 𝑝 = 0.031, forthe mouse game. This means players were more likely to enjoy
when they were playing a mouse-game with wiping operation.
On the other hand, the p-value, 𝑝 = 0.156, for the hand-gamedoes not show a significant difference. When some players
played the hand-game, the Kinect sensor was out of control
when they went far from the play space. We consider that, insuch a situation, the players must have been frustrated or
irritable. Thus, we infer that the Kinect sensor’s response
problem was one serious reason for the high score oftension/annoyance factor and made p-value high.

5

Score [1-strongly agreeing; 3-agree; 5-strongly agree]with a wiping operation

1.5

Negative affect

4.25

Competence0and “positive effect” are more than 4.

without a wiping operation

Figure 10: Questionnaire result of mouse-game
Figure 11 shows the questionnaire result of the hand-game.
The questionnaire was filled in after the gameplay in the same
way as the mouse-game. In the same way as the mouse-game,“negative affect” and “tension/annoyance” are given lowscores and other factors are given high scores. This means thatour games are given good evaluation. After this, we consider 5factors other than “negative affect” and “tension/annoyance”.
The game with wiping operation is given higher scores than thegame without wiping operation for all factors. Especially,“challenge” has larger difference, which is approximately 0.65,
than other factors. In the hand-game, the player moves hands
actively when moving their body parts. Thus, this play stylemight make the player improve the challenging spirit [19, 20].
The scores of “sensory and imaginative immersion”, “flow”,
238

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)

Table 3. The probability result of questionnaire result
Mouse-gamewith wiping operation, and 1 player has the same values.
Among 8 players with higher values for the game with wiping
operation, the player 9 has the highest score, 75, in the gamewith wiping operation, and also has the largest difference, 30,
between the games with and without wiping operation. The
player 2 has the second highest score, 62, in the game withwiping operation, and has the second largest difference, 21,
between the two games. The player 8 is the only player who
has higher score, 52, in the game without wiping operation, andthe difference between the two games is only 1. As a whole,most of the players tend to have higher scores in the game withwiping operation, and some players have large differences
between the two games.

Hand-game𝑝 value
Without wiping operation

0.031*

With wiping operation

0.156

𝑝 < .05

5.2 Brain activity result

Brain score

During the gameplay, the player wore a headband with a XB01 brain sensor over the left eyebrow on the forehead. The
sensor was connected to an iPhone using Bluetooth for datacollection. XB-01 measures real-time brain activity, by bloodflow volume during the exercise program. After the gameplay,
the application of XB-01 gives us one brain activity value by
the score from 0 to 100; 100 means brain activity is the highest
while 0 is the lowest.
Figure 12 and Figure 13 show the brain activity result of themouse-game and hand-game. The horizontal value represents
the players' numbers while the vertical value represents theirbrain activity values. In Figure 12, the game without wiping
operation has the maximum 53 and the minimum 18, and thegame with wiping operation has the maximum 70 and theminimum 29. Among 16 players, 4 players have higher values
for the game without wiping operation, 7 players have higher
values for the game with wiping operation, and 2 players havethe same values. Among 10 players with higher values for thegame with wiping operation, the player 13 has the highest score,70, in the game with wiping operation, and also has the largest
difference, 36, between the games with and without wiping
operation. The player 2 has the second highest score, 62, in thegame with wiping operation, and has the second largest
difference, 29, between the two games. Among 4 players withhigher values for the game without wiping operation, the player
8 has the highest score, 52, in the game without wiping
operation, and also has the largest difference, 10, between thetwo games. As a whole, large number of the players tend tohave higher scores in the game with wiping operation, andsome players have large differences between the two games.

80
70
60
50
40
30
20
10
0

75

51
42

62
53

1

2

3

54
47

50
47

48
42

41

40

4

5

42
38

6

7

47

45

41

52

8

9

10

Player number
without a wiping operation

with a wiping operation

Figure 13: Brain activity result of hand-game
Table 4 provides the probability result of the Brain activity.
The differences between the game without wiping operation
and with wiping operation on both of the mouse-game, 𝑝 =0.035, and the hand-game, 𝑝 = 0.015, are significant because
the p-values are lesser than 0.05. As a result, the wiping
operation gave more enjoyment to players while they wereplaying the game with it. From the questionnaire and brain
activity results in the experiment, the wiping operation
accelerates human activity and gives more enjoyment toplayers in hidden object games.
Table 4. The probability result of brain activity
Mouse-gameHand-game

Brain score

𝑝-value
Without wiping operation

80
70
60
50
40
30
20
10
0

54

62
52
39

33

49 47
39

70

44 47

53
38
36 34
29

52
42 45

62
52 49
46

47 47

50
34

With wiping operation

59
53

2

3

4

5

6

7

8

6. Conclusion

31This paper presented the wiping operation, to accelerate
human activity on a hidden object game. In the games to findobjects in a triangulated image by mouse and hands, the wiping
operation works well to activate human brain efficiently. By the
Wilcoxon test analysis, the brain activity data showedsignificant differences between both of the mouse and handgames without and with wiping operation and the effectivenessof wiping operation. In addition, the questionnaire result of themouse-game also showed the effectiveness of wiping operation.
However, the questionnaire result of the hand-game was not an
expective result mainly due to the limitation of the Kinect
sensor’s sensing range. Overall, the wiping operation is highly

9 10 11 12 13 14 15 16Player number
without a wiping operation

0.015*

𝑝 < .0518

10.035*

with a wiping operation

Figure 12: Brain activity result of mouse-game
In Figure 13, the game without wiping operation has the
maximum 52 and the minimum 38. The game with wiping
operation has the maximum 75, and the minimum 42. Among
10 players, 1 player has higher values for the game without
wiping operation, 6 players have higher values for the game
239

The Journal of the Society for Art and Science, Vol. 21, No. 4, pp. 233-240 (2022)

effective on HOG as we hypothesized. In the future, we needto investigate the effect of the wiping operation more. In
addition, we are planning to apply the wiping operation to othertypes of games.

[14] Y. Toyoshima, "Mosaic Quiz - guess the word ofpixelated
images,"[Online].
Available:
https://appadvice.com/app/mosaic-quiz-guess-the-wordof-pixelated-images/1211611274. [Accessed 05 03
2022].
[15] J. Puckey, "Delaunay Raster," [Online]. Available:
https://www.jonathanpuckey.com/projects/delaunayraster/. [Accessed 18 11 2019].
[16] M. Chevalier, "L'Oeil de la machine 2019," Miguel
Chevalier,
2020.
[Online].
Available:
https://www.miguel-chevalier.com/work/loeil-de-lamachine. [Accessed 03 05 2022].
[17] O. Devillers, "Improved incremental randomized
Delaunay triangulation," arXiv preprint cs/9907024,
1999.
[18] O. Devillers, "Vertex removal in two-dimensional
Delaunay triangulation:Speed-up by low degrees
optimization," Computational Geometry, vol. 44, no. 3,
pp. 169-177, 2011.
[19] A. Corcos, "Being enjoyably challenged is the key to an
enjoyable gaming experience: an experimental approachin a first-person shooter game," Socioaffective
Neuroscience & Psychology, vol. 8, no. 1, p. 1474668,
2018.
[20] J. Vahlo and V. M. Karhulahti, "Challenge types ingaming validation of video game challenge inventory(CHA)," International Journal of Human-Computer
Studies, vol. 143, p. 102473, 2020.

References[1] "G5 Games - The Secret Society® - Seek & Find Hidden
Objects," 20 04 2022. [Online]. Available:
https://g5e.com/games/the-secret-society-hiddenmystery.
[2] "G5 Games - Hidden City®: Hidden Objects &Pictures," 20 04 2022. [Online]. Available:
https://g5e.com/games/hidden-city.
[3] K. Ehm and K. Ehm, "Measuring game immersion andflow with electroencephalography," in IADISInternational Conference Interfaces and Human
Computer Interaction, 2021.
[4] M. Abujelala, C. Abellanoza, A. Sharma and F.
Makedon, "Brain-EE: Brain Enjoyment Evaluation using
Commercial EEG Headband," in PETRA '16:
Proceedings of the 9th ACM International Conference on
PErvasive Technologies Related to Assistive
Environments, Gorfu, Greece, 2016.
[5] J. Feng, Y. Ni, J. Dong, Z. Wang and S. Yan, "Purposive
hidden-object-game: Embedding human computation in
popular game," IEEE Transactions on Multimedia, vol.
14, no. 5, pp. 1496-1507, 2012.
[6] E. A. Alghamdi, "Untangling Multimedia Effects on EFL
Incidental Vocabulary Learning via Playing an Online
Hidden-Object Game," International Journal ofComputer-Assisted Language Learning and Teaching(IJCALLT), vol. 6, no. 1, pp. 24-39, 2016.
[7] M. Sailer, J. U. Hense, S. K. Mayr and H. Mandl, "Howgamification motivates: An experimental study of theeffects of specific game design elements on
psychological need satisfaction," Computers in Human
Behavior, vol. 69, pp. 371-380, 2017.
[8] J. Wiemeyer, L. Nacke, C. Moser and F. ‘Floyd’ Mueller,"Player Experience," Serious Games, pp. 243-271, 2016.
[9] W. IJsselsteijn, Y. de Kort and K. Poels, "The Game
Experience Questionnaire," Technische Universiteit
Eindhoven https://research.tue.nl/en/publications/thegame-experience-questionnaire, 2013.
[10] A. M. Ledbetter, S. H. Taylor and J. P. Mazer,"Enjoyment fosters media use frequency and determines
its relational outcomes: Toward a synthesis of uses andgratifications theory and media multiplexity theory,"
Computers in Human Behavior, vol. 54, pp. 149-157,
2016.
[11] B. P. Acevedo, N. Dattatri, J. Le, C. Lappinga and N. L.
Collins, "Cognitive Training with Neurofeedback Using
fNIRS Improves Cognitive Function in Older Adults,"
International Journal of Environmental Research andPublic Health, vol. 19, no. 9, p. 5531, 2022.
[12] "Find The Word - Reveal the the picture, guess the wordand spin the wheel! by Rohn Media GmbH," AppAdvice,[Online]. Available: https://appadvice.com/app/findword-reveal-picture-guess-word-spinwheel/624008178. [Accessed 05 03 2022].
[13] "unblur.app - Picture Quiz," Sparse creations UG, 2019.
[Online].
Available:
https://apps.apple.com/jp/app/unblur-app-picturequiz/id1423593835. [Accessed 02 2022].

Appendix
Game Experience Questionnaire

240

QuestionsGame factors

1

I was interested in the game's
story

Sensory andImaginative Immersion

2

I felt successfulCompetence3

I felt bored

Negative affect4

I found it impressive

Sensory andImaginative Immersion

5

I forgot everything around me

Flow

6

I felt frustrated

Tension/Annoyance7

I found it tiresome

Negative affect8

I felt irritable

Tension/Annoyance9

I felt skillfulCompetence10

I was fully occupied with the
game

Flow

11

I felt content

Positive affect12

I felt challenged

Challenge

13

I had to put a lot of effort into it

Challenge

14

I felt good

Positive affect