<s>
A	O
tile-matching	B-Application
video	I-Application
game	I-Application
is	O
a	O
type	O
of	O
puzzle	O
video	O
game	O
where	O
the	O
player	O
manipulates	O
tiles	O
in	O
order	O
to	O
make	O
them	O
disappear	O
according	O
to	O
a	O
matching	O
criterion	O
.	O
</s>
<s>
In	O
many	O
tile-matching	B-Application
games	I-Application
,	O
that	O
criterion	O
is	O
to	O
place	O
a	O
given	O
number	O
of	O
tiles	O
of	O
the	O
same	O
type	O
so	O
that	O
they	O
adjoin	O
each	O
other	O
.	O
</s>
<s>
That	O
number	O
is	O
often	O
three	O
,	O
and	O
these	O
games	O
are	O
called	O
match-three	B-Application
games	I-Application
.	O
</s>
<s>
The	O
core	O
challenge	O
of	O
tile-matching	B-Application
games	I-Application
is	O
the	O
identification	O
of	O
patterns	O
on	O
a	O
seemingly	O
chaotic	O
board	O
.	O
</s>
<s>
Their	O
origins	O
lie	O
in	O
puzzle	O
games	O
from	O
the	O
1980s	O
such	O
as	O
Tetris	B-Application
,	O
Chain	B-Application
Shot	I-Application
!	I-Application
</s>
<s>
(	O
SameGame	B-Application
)	O
and	O
Puzznic	B-Application
.	O
</s>
<s>
Tile-matching	B-Application
games	I-Application
were	O
made	O
popular	O
in	O
the	O
2000s	O
,	O
in	O
the	O
form	O
of	O
casual	O
games	O
distributed	O
or	O
played	O
over	O
the	O
Internet	O
,	O
notably	O
the	O
Bejeweled	B-Device
series	O
of	O
games	O
.	O
</s>
<s>
They	O
have	O
remained	O
popular	O
since	O
,	O
with	O
the	O
game	O
Candy	B-Application
Crush	I-Application
Saga	I-Application
becoming	O
the	O
most-played	O
game	O
on	O
Facebook	B-Application
in	O
2013	O
.	O
</s>
<s>
Tile-matching	B-Application
games	I-Application
cover	O
a	O
broad	O
range	O
of	O
design	O
elements	O
,	O
mechanics	O
and	O
gameplay	O
experiences	O
.	O
</s>
<s>
They	O
include	O
purely	O
turn-based	O
games	O
but	O
may	O
also	O
feature	O
arcade-style	O
action	B-Application
elements	O
such	O
as	O
time	O
pressure	O
,	O
shooting	O
or	O
hand-eye	O
coordination	O
.	O
</s>
<s>
The	O
mechanism	O
of	O
matching	O
game	O
pieces	O
to	O
make	O
them	O
disappear	O
is	O
a	O
feature	O
of	O
many	O
non-digital	O
games	O
,	O
including	O
Mahjong	B-Application
solitaire	I-Application
and	O
Solitaire	B-Algorithm
card	O
games	O
.	O
</s>
<s>
Video	O
game	O
researcher	O
Jesper	O
Juul	O
traces	O
the	O
history	O
of	O
tile-matching	B-Application
video	I-Application
games	I-Application
back	O
to	O
early	O
puzzle	O
Tetris	B-Application
and	O
Chain	B-Application
Shot	I-Application
!	I-Application
</s>
<s>
(	O
later	O
known	O
as	O
SameGame	B-Application
)	O
,	O
published	O
in	O
1984	O
and	O
1985	O
,	O
respectively	O
.	O
</s>
<s>
While	O
there	O
may	O
have	O
been	O
earlier	O
video	O
games	O
with	O
tile-matching	B-Application
mechanics	O
,	O
Juul	O
stated	O
that	O
the	O
commercial	O
success	O
of	O
both	O
Tetris	B-Application
and	O
Chain	B-Application
Shot	I-Application
!	I-Application
</s>
<s>
established	O
the	O
popularity	O
of	O
puzzle	O
games	O
,	O
leading	O
to	O
a	O
second	O
generation	O
of	O
influential	O
games	O
–	O
Puzznic	B-Application
,	O
Columns	B-Application
,	O
Dr.	B-Application
Mario	I-Application
and	O
Plotting	B-Application
–	O
which	O
were	O
published	O
in	O
1989	O
and	O
1990	O
.	O
</s>
<s>
Another	O
early	O
Mahjong-style	O
pair	O
matching	O
game	O
was	O
Shanghai	B-Device
(	O
1986	O
)	O
.	O
</s>
<s>
The	O
popularity	O
of	O
the	O
puzzle	O
genre	O
was	O
further	O
boosted	O
when	O
Nintendo	O
bundled	O
the	O
Game	B-Device
Boy	I-Device
version	O
of	O
Tetris	B-Application
with	O
the	O
Game	B-Device
Boy	I-Device
handheld	O
system	O
upon	O
its	O
North	O
American	O
and	O
European	O
releases	O
in	O
1989	O
.	O
</s>
<s>
The	O
game	O
helped	O
to	O
sell	O
the	O
handheld	O
system	O
,	O
making	O
it	O
a	O
killer	O
application	O
,	O
and	O
sold	O
over	O
35	O
million	O
copies	O
over	O
the	O
Game	B-Device
Boy	I-Device
's	O
lifetime	O
.	O
</s>
<s>
As	O
it	O
drew	O
in	O
players	O
that	O
normally	O
did	O
not	O
play	O
video	O
games	O
,	O
Tetris	B-Application
is	O
considered	O
one	O
of	O
the	O
first	O
casual	O
games	O
.	O
</s>
<s>
Games	O
building	O
on	O
Dr.	O
Mario'''s	O
mechanics	O
include	O
Puyo	B-Application
Puyo	I-Application
(	O
1991	O
)	O
,	O
Baku	B-Application
Baku	I-Application
Animal	I-Application
(	O
1995	O
)	O
and	O
Puzzle	B-Application
Fighter	I-Application
(	O
1996	O
)	O
.	O
</s>
<s>
Building	O
on	O
the	O
shooting	O
mechanic	O
introduced	O
in	O
Plotting	B-Application
,	O
Dr.	B-Application
Mario	I-Application
also	O
influenced	O
Puzzle	B-Application
Bobble	I-Application
(	O
1994	O
)	O
,	O
which	O
in	O
turn	O
inspired	O
Puzz	B-Application
Loop	I-Application
(	O
1998	O
)	O
,	O
Hexic	B-Application
and	O
Zuma	B-Application
(	O
2003	O
)	O
,	O
and	O
Luxor	B-Language
(	O
2005	O
)	O
.	O
</s>
<s>
Columns	B-Application
was	O
the	O
basis	O
of	O
a	O
line	O
of	O
development	O
of	O
tile	O
matching	O
games	O
based	O
on	O
shifting	O
or	O
swapping	O
tiles	O
.	O
</s>
<s>
It	O
includes	O
Yoshi	B-Application
's	I-Application
Cookie	I-Application
(	O
1992	O
)	O
and	O
Panel	O
de	O
Pon	O
(	O
1995	O
)	O
,	O
which	O
introduced	O
the	O
swapping	O
mechanic	O
.	O
</s>
<s>
Puzzled	B-Application
included	O
multiplayer	O
games	O
and	O
was	O
released	O
for	O
the	O
Neo	O
Geo	O
console	O
in	O
the	O
same	O
year	O
.	O
</s>
<s>
1994	O
saw	O
BreakThru	B-Application
!	I-Application
</s>
<s>
and	O
Gururin	B-Application
published	O
with	O
FlipOut	B-Application
!	I-Application
</s>
<s>
and	O
Vid	B-Application
Grid	I-Application
released	O
the	O
following	O
year	O
.	O
</s>
<s>
Hebereke	B-Application
's	I-Application
Popoitto	I-Application
was	O
released	O
in	O
1995	O
containing	O
a	O
two	O
player	O
competitive	O
game	O
.	O
</s>
<s>
Sega	B-Application
Swirl	I-Application
for	O
handheld	O
devices	O
was	O
released	O
in	O
1999	O
.	O
</s>
<s>
Microsoft	O
bundled	O
Jawbreaker	B-Language
Windows	O
Mobile	O
2003	O
.	O
</s>
<s>
Several	O
multiplayer	O
modes	O
,	O
both	O
local	O
and	O
networked	O
,	O
featured	O
in	O
early	O
tile-matching	B-Application
games	I-Application
such	O
as	O
Columns	B-Application
and	O
Dr.	B-Application
Mario	I-Application
and	O
later	O
with	O
TetriNET	B-Application
(	O
1997	O
)	O
and	O
Tetris	B-Application
Worlds	O
(	O
2001	O
)	O
.	O
</s>
<s>
The	O
first	O
of	O
what	O
eventually	O
became	O
known	O
as	O
"	O
match-three	B-Application
"	O
games	O
,	O
where	O
the	O
goal	O
is	O
to	O
create	O
clusters	O
of	O
three	O
or	O
more	O
identical	O
items	O
on	O
a	O
grid	O
,	O
was	O
Shariki	B-Application
(	O
1994	O
)	O
.	O
</s>
<s>
It	O
led	O
directly	O
to	O
the	O
successful	O
Bejeweled	B-Device
(	O
2001	O
)	O
,	O
which	O
became	O
a	O
series	O
and	O
inspired	O
similar	O
games	O
including	O
Zoo	B-Device
Keeper	I-Device
(	O
2003	O
)	O
,	O
Big	B-Application
Kahuna	I-Application
Reef	I-Application
(	O
2004	O
)	O
,	O
Jewel	B-Application
Quest	I-Application
(	O
2004	O
)	O
,	O
and	O
Chuzzle	B-Operating_System
(	O
2005	O
)	O
.	O
</s>
<s>
Tidalis	B-Application
(	O
2010	O
)	O
developed	O
the	O
idea	O
further	O
with	O
20	O
game	O
modes	O
and	O
the	O
goal	O
of	O
creating	O
the	O
longest	O
possible	O
chain	O
of	O
matching	O
colors	O
.	O
</s>
<s>
Towards	O
2010	O
,	O
new	O
trends	O
in	O
tile-matching	B-Application
games	I-Application
appeared	O
.	O
</s>
<s>
The	O
first	O
was	O
driven	O
by	O
the	O
popularity	O
of	O
mobile	B-Application
games	I-Application
.	O
</s>
<s>
Prior	O
to	O
2012	O
,	O
most	O
tile-matching	B-Application
games	I-Application
had	O
no	O
end	O
goal	O
,	O
instead	O
challenging	O
the	O
player	O
to	O
continue	O
as	O
long	O
as	O
possible	O
until	O
the	O
board	O
reached	O
a	O
state	O
where	O
no	O
turn	O
was	O
possible	O
,	O
or	O
,	O
in	O
the	O
case	O
of	O
Tetris	B-Application
,	O
where	O
tiles	O
have	O
filled	O
up	O
past	O
a	O
given	O
point	O
on	O
the	O
board	O
.	O
</s>
<s>
King	O
,	O
which	O
had	O
made	O
similar	O
tile-matching	B-Application
games	I-Application
for	O
browser-based	O
games	O
,	O
explored	O
a	O
different	O
approach	O
with	O
its	O
first	O
mobile	O
app	O
,	O
Bubble	O
Witch	O
Saga	O
,	O
which	O
had	O
puzzle-oriented	O
gameplay	O
like	O
Puzzle	B-Application
Bobble	I-Application
,	O
but	O
applied	O
finite	O
restrictions	O
on	O
the	O
number	O
of	O
moves	O
the	O
player	O
could	O
take	O
and	O
setting	O
target	O
goals	O
such	O
as	O
score	O
or	O
clearing	O
the	O
board	O
.	O
</s>
<s>
This	O
approach	O
proved	O
highly	O
successful	O
and	O
King	O
reused	O
it	O
for	O
the	O
tile-matching	B-Application
game	I-Application
Candy	B-Application
Crush	I-Application
Saga	I-Application
in	O
2012	O
,	O
itself	O
which	O
was	O
inspired	O
by	O
Bejeweled	B-Device
.	O
</s>
<s>
Candy	B-Application
Crush	I-Application
Saga	I-Application
became	O
one	O
of	O
the	O
most	O
financially	O
successful	O
mobile	B-Application
games	I-Application
,	O
and	O
established	O
a	O
new	O
type	O
of	O
tile-matching	B-Application
game	I-Application
based	O
on	O
creating	O
games	O
broken	O
up	O
into	O
levels	O
and	O
establishing	O
goals	O
to	O
reach	O
within	O
a	O
limited	O
number	O
of	O
moves	O
.	O
</s>
<s>
This	O
"	O
saga	O
"	O
approach	O
also	O
extended	O
to	O
other	O
genres	O
of	O
mobile	B-Application
games	I-Application
.	O
</s>
<s>
The	O
second	O
innovation	O
in	O
tile-matching	B-Application
games	I-Application
was	O
the	O
incorporation	O
of	O
their	O
mechanic	O
into	O
other	O
genres	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
such	O
games	O
was	O
Puzzle	B-Application
Quest	I-Application
:	I-Application
Challenge	I-Application
of	I-Application
the	I-Application
Warlords	I-Application
released	O
in	O
2008	O
.	O
</s>
<s>
While	O
based	O
on	O
a	O
Bejeweled-like	O
tile-matching	B-Application
game	I-Application
,	O
Puzzle	O
Quest	O
added	O
elements	O
of	O
a	O
computer	O
role-playing	O
game	O
atop	O
this	O
.	O
</s>
<s>
Puzzle	O
Quest	O
was	O
very	O
popular	O
and	O
led	O
to	O
numerous	O
games	O
which	O
uses	O
the	O
tile-matching	B-Application
as	O
part	O
of	O
a	O
battle	O
system	O
.	O
</s>
<s>
While	O
not	O
directly	O
influenced	O
by	O
Puzzle	O
Quest	O
,	O
Puzzle	B-Application
&	I-Application
Dragons	I-Application
in	O
2012	O
was	O
another	O
successful	O
mobile	O
title	O
that	O
used	O
the	O
tile-matching	B-Application
part	O
of	O
the	O
game	O
for	O
combat-related	O
actions	O
.	O
</s>
<s>
Both	O
Push	B-Application
Panic	I-Application
and	O
Heroes	O
of	O
Kalevala	O
arrived	O
in	O
2010	O
.	O
</s>
<s>
In	O
2011	O
New	B-Operating_System
Puzzle	I-Operating_System
Bobble	I-Operating_System
was	O
released	O
for	O
iOS	O
while	O
Bubble	B-Application
Safari	I-Application
,	O
Ruby	B-Application
Blast	I-Application
,	O
Gems	B-Application
with	I-Application
Friends	I-Application
and	O
Puzzle	B-Application
&	I-Application
Dragons	I-Application
were	O
first	O
released	O
in	O
2012	O
.	O
</s>
<s>
Juice	B-Application
Cubes	I-Application
,	O
Tower	B-Application
of	I-Application
Saviors	I-Application
,	O
Alien	B-Application
Hive	I-Application
,	O
Marvel	B-Application
Puzzle	I-Application
Quest	I-Application
,	O
Jelly	B-Application
Splash	I-Application
and	O
Doctor	B-Application
Who	I-Application
:	I-Application
Legacy	I-Application
were	O
released	O
for	O
mobile	O
devices	O
from	O
2013	O
onwards	O
.	O
</s>
<s>
In	O
2015	O
Dragon	B-Application
Ball	I-Application
Z	I-Application
:	I-Application
Dokkan	I-Application
Battle	I-Application
,	O
Ironcast	B-Application
,	O
HuniePop	B-Application
,	O
Hex	B-Application
Frvr	I-Application
and	O
Sailor	B-Application
Moon	I-Application
Drops	I-Application
were	O
all	O
released	O
.	O
</s>
<s>
By	O
2016	O
millions	O
of	O
players	O
were	O
logging	O
into	O
titles	O
such	O
as	O
Gardenscapes	B-Application
:	I-Application
New	I-Application
Acres	I-Application
.	O
</s>
<s>
The	O
genre	O
continues	O
to	O
appeal	O
to	O
gamers	O
,	O
with	O
numerous	O
titles	O
including	O
Boost	B-Device
Beast	I-Device
(	O
2017	O
)	O
,	O
Dr.	B-Application
Mario	I-Application
World	I-Application
,	O
and	O
Crystal	B-Application
Crisis	I-Application
(	O
2019	O
)	O
among	O
the	O
more	O
recent	O
.	O
</s>
<s>
A	O
new	O
style	O
of	O
tile-matching	B-Application
game	I-Application
arose	O
from	O
games	O
like	O
Triple	B-Application
Town	I-Application
(	O
2010	O
)	O
,	O
2048	B-Application
(	O
2014	O
)	O
,	O
and	O
Threes	B-Application
(	O
2014	O
)	O
,	O
typically	O
called	O
merge-style	O
games	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
2048	B-Application
,	O
players	O
are	O
given	O
random	O
blocks	O
with	O
numbers	O
2	O
or	O
4	O
on	O
them	O
,	O
and	O
much	O
match	O
two	O
blocks	O
of	O
the	O
same	O
number	O
as	O
to	O
generate	O
new	O
blocks	O
with	O
values	O
in	O
the	O
multiples	O
of	O
2	O
,	O
with	O
the	O
goal	O
to	O
try	O
to	O
get	O
a	O
block	O
with	O
the	O
value	O
2048	B-Application
(	O
211	O
)	O
or	O
higher	O
.	O
</s>
<s>
While	O
the	O
merging	O
mechanic	O
had	O
been	O
part	O
of	O
other	O
video	O
games	O
since	O
as	O
early	O
as	O
Darwin	B-Application
's	I-Application
Dilemma	I-Application
in	O
1990	O
,	O
the	O
genre	O
saw	O
a	O
boost	O
following	O
the	O
success	O
of	O
Threes	B-Application
on	O
mobile	O
platforms	O
.	O
</s>
<s>
Early	O
puzzle	O
games	O
like	O
Tetris	B-Application
were	O
timed	O
–	O
that	O
is	O
,	O
new	O
tiles	O
are	O
continuously	O
added	O
and	O
the	O
player	O
is	O
under	O
pressure	O
to	O
make	O
matches	O
before	O
the	O
board	O
fills	O
up	O
.	O
</s>
<s>
Untimed	O
(	O
turn-based	O
)	O
games	O
,	O
in	O
which	O
new	O
tiles	O
are	O
added	O
only	O
after	O
the	O
player	O
has	O
made	O
a	O
move	O
,	O
used	O
to	O
be	O
the	O
exception	O
,	O
although	O
the	O
1985	O
game	O
Chain	B-Application
Shot	I-Application
!	I-Application
</s>
<s>
The	O
addition	O
of	O
an	O
untimed	O
mode	O
to	O
Bejeweled	B-Device
!	O
</s>
<s>
With	O
the	O
introduction	O
of	O
Candy	B-Application
Crush	I-Application
Saga	I-Application
,	O
games	O
with	O
levels	O
featuring	O
limits	O
on	O
the	O
number	O
of	O
moves	O
were	O
introduced	O
.	O
</s>
<s>
In	O
the	O
latter	O
case	O
,	O
some	O
games	O
allow	O
moving	O
or	O
rotating	O
new	O
tiles	O
as	O
they	O
fall	O
down	O
from	O
the	O
top	O
of	O
the	O
playing	O
area	O
,	O
as	O
in	O
Tetris	B-Application
or	O
Dr.	B-Application
Mario	I-Application
;	O
or	O
they	O
may	O
allow	O
only	O
the	O
manipulation	O
of	O
tiles	O
that	O
have	O
already	O
fallen	O
,	O
as	O
in	O
Yoshi	O
's	O
Cookie.Panel	O
de	O
Pon	O
introduced	O
,	O
and	O
Bejeweled	B-Device
popularized	O
the	O
mechanism	O
of	O
tile	O
swapping	O
,	O
in	O
which	O
tiles	O
may	O
be	O
moved	O
by	O
exchanging	O
the	O
position	O
of	O
two	O
adjacent	O
tiles	O
.	O
</s>
<s>
Another	O
frequently	O
used	O
tile	O
manipulation	O
method	O
is	O
having	O
the	O
player	O
shoot	O
the	O
tiles	O
onto	O
the	O
board	O
,	O
such	O
as	O
in	O
Plotting	B-Application
and	O
its	O
descendants	O
including	O
Zuma	B-Application
.	O
</s>
<s>
In	O
most	O
tile-matching	B-Application
games	I-Application
,	O
players	O
obtain	O
points	O
for	O
each	O
match	O
.	O
</s>
<s>
In	O
some	O
tile	O
games	O
,	O
when	O
tiles	O
are	O
matched	O
and	O
removed	O
,	O
pieces	O
above	O
them	O
fall	O
to	O
fill	O
the	O
space	O
(	O
as	O
with	O
Bejeweled	B-Device
and	O
Candy	O
Crush	O
Saga''	O
)	O
.	O
</s>
<s>
In	O
most	O
tile-matching	B-Application
games	I-Application
,	O
new	O
tiles	O
are	O
randomly	O
added	O
to	O
the	O
board	O
continuously	O
,	O
either	O
turn	O
by	O
turn	O
or	O
in	O
real	O
time	O
.	O
</s>
<s>
Among	O
downloadable	O
casual	O
video	O
games	O
,	O
according	O
to	O
a	O
survey	O
referred	O
to	O
by	O
Juul	O
,	O
tile-matching	B-Application
games	I-Application
were	O
the	O
second	O
most	O
popular	O
game	O
type	O
in	O
2004	O
and	O
by	O
far	O
the	O
most	O
popular	O
in	O
2005	O
.	O
</s>
<s>
But	O
as	O
they	O
became	O
well	O
known	O
and	O
therefore	O
assumed	O
to	O
be	O
immediately	O
playable	O
by	O
many	O
people	O
,	O
tile-matching	B-Application
games	I-Application
migrated	O
to	O
other	O
,	O
more	O
ubiquitous	O
distribution	O
channels	O
such	O
as	O
cell	O
phones	O
and	O
smartphones	O
.	O
</s>
<s>
Despite	O
their	O
commercial	O
popularity	O
,	O
tile-matching	B-Application
games	I-Application
are	O
among	O
the	O
games	O
with	O
the	O
lowest	O
status	O
among	O
video	O
game	O
enthusiasts	O
,	O
to	O
the	O
point	O
where	O
reviewers	O
have	O
advised	O
gamers	O
not	O
to	O
be	O
ashamed	O
of	O
playing	O
them	O
.	O
</s>
<s>
It	O
may	O
also	O
be	O
because	O
,	O
as	O
casual	O
games	O
,	O
tile-matching	B-Application
games	I-Application
are	O
designed	O
to	O
be	O
easily	O
accessible	O
and	O
easy	O
to	O
play	O
,	O
which	O
conflicts	O
with	O
a	O
traditional	O
video	O
gaming	O
ethos	O
that	O
demands	O
games	O
to	O
be	O
challenging	O
and	O
punishing	O
.	O
</s>
<s>
Match-three	B-Application
games	I-Application
are	O
NP-hard	O
when	O
generalized	O
to	O
an	O
playfield	O
and	O
played	O
such	O
that	O
the	O
player	O
knows	O
in	O
advance	O
all	O
the	O
tiles	O
that	O
will	O
appear	O
,	O
with	O
no	O
random	O
chance	O
involved	O
.	O
</s>
