<s>
It	O
is	O
the	O
spiritual	O
sequel	O
to	O
Radiant	B-Application
Silvergun	I-Application
(	O
1998	O
)	O
and	O
was	O
originally	O
released	O
in	O
Japanese	O
arcades	O
in	O
December	O
2001	O
.	O
</s>
<s>
The	O
story	O
follows	O
a	O
rebel	O
pilot	O
named	O
Shinra	O
as	O
he	O
battles	O
an	O
enemy	O
nation	O
using	O
a	O
specially	O
designed	O
fighter	O
called	O
the	O
Ikaruga	B-Application
which	O
can	O
flip	O
between	O
two	O
polarities	O
,	O
black	O
and	O
white	O
.	O
</s>
<s>
Development	O
on	O
Ikaruga	B-Application
began	O
during	O
director	O
Hiroshi	O
Iuchi	O
's	O
off-hours	O
while	O
Treasure	O
was	O
busy	O
developing	O
Sin	B-Application
and	I-Application
Punishment	I-Application
(	O
2000	O
)	O
.	O
</s>
<s>
Titled	O
"	O
Project	O
RS2	O
"	O
,	O
the	O
game	O
began	O
as	O
a	O
sequel	O
to	O
Radiant	B-Application
Silvergun	I-Application
,	O
and	O
borrows	O
many	O
elements	O
from	O
it	O
as	O
well	O
as	O
the	O
polarity	O
mechanism	O
from	O
Treasure	O
's	O
Silhouette	B-Application
Mirage	I-Application
(	O
1997	O
)	O
.	O
</s>
<s>
During	O
the	O
game	O
's	O
prototype	B-Application
stages	O
,	O
the	O
player	O
's	O
ammo	O
was	O
limited	O
.	O
</s>
<s>
In	O
tradition	O
with	O
Treasure	O
's	O
game	O
design	O
philosophy	O
,	O
Ikaruga	B-Application
was	O
intentionally	O
crafted	O
to	O
challenge	O
the	O
conventions	O
of	O
standard	O
game	O
design	O
and	O
develop	O
a	O
new	O
type	O
of	O
shooting	O
game	O
.	O
</s>
<s>
All	O
together	O
,	O
five	O
Treasure	O
staff	O
worked	O
on	O
Ikaruga	B-Application
,	O
as	O
well	O
as	O
three	O
support	O
staff	O
from	O
G.rev	O
.	O
</s>
<s>
In	O
2002	O
,	O
Ikaruga	B-Application
was	O
ported	O
to	O
the	B-Operating_System
Dreamcast	I-Operating_System
in	O
Japan	O
and	O
began	O
to	O
grow	O
a	O
cult	O
following	O
from	O
import	O
gamers	O
worldwide	O
.	O
</s>
<s>
It	O
was	O
later	O
released	O
in	O
the	O
West	O
in	O
2003	O
on	O
the	O
GameCube	B-Application
,	O
receiving	O
positive	O
reviews	O
.	O
</s>
<s>
Ikaruga	B-Application
was	O
later	O
ported	O
to	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
,	O
Microsoft	B-Application
Windows	I-Application
,	O
Nintendo	B-Application
Switch	I-Application
and	O
PlayStation	B-Operating_System
4	I-Operating_System
.	O
</s>
<s>
In	O
retrospect	O
,	O
Ikaruga	B-Application
is	O
regarded	O
by	O
critics	O
as	O
one	O
of	O
the	O
best	O
games	O
ever	O
made	O
,	O
especially	O
in	O
the	O
shoot	O
'	O
em	O
up	O
genre	O
,	O
and	O
one	O
of	O
Treasure	O
's	O
greatest	O
works	O
.	O
</s>
<s>
Ikaruga	B-Application
is	O
a	O
vertically	O
scrolling	O
shoot	O
'	O
em	O
up	O
.	O
</s>
<s>
The	O
player	O
pilots	O
the	O
Ikaruga	B-Application
fighter	O
,	O
moving	O
to	O
avoid	O
obstacles	O
and	O
other	O
danger	O
.	O
</s>
<s>
A	O
key	O
gameplay	O
feature	O
to	O
Ikaruga	B-Application
is	O
its	O
polarity	O
system	O
.	O
</s>
<s>
Ikaruga	B-Application
does	O
not	O
feature	O
any	O
pick-ups	O
or	O
power-ups	O
,	O
instead	O
,	O
the	O
player	O
can	O
only	O
rely	O
on	O
their	O
standard	O
firing	O
weapon	O
and	O
a	O
homing	O
laser	O
.	O
</s>
<s>
Home	O
console	O
ports	O
of	O
Ikaruga	B-Application
feature	O
additional	O
gameplay	O
modes	O
apart	O
from	O
the	O
standard	O
arcade	O
mode	O
.	O
</s>
<s>
If	O
certain	O
conditions	O
are	O
met	O
,	O
a	O
prototype	B-Application
mode	O
is	O
unlocked	O
which	O
limits	O
the	O
number	O
of	O
bullets	O
the	O
player	O
has	O
.	O
</s>
<s>
Shinra	O
set	O
off	O
to	O
battle	O
Horai	O
again	O
,	O
but	O
he	O
was	O
shot	O
down	O
and	O
crashed	O
in	O
a	O
remote	O
village	O
called	O
Ikaruga	B-Application
.	O
</s>
<s>
The	O
villagers	O
entrusted	O
him	O
with	O
a	O
fighter	O
plane	O
they	O
had	O
built	O
themselves	O
called	O
the	O
Ikaruga	B-Application
,	O
which	O
was	O
specially	O
designed	O
and	O
hidden	O
away	O
in	O
a	O
secret	O
underground	O
location	O
beneath	O
the	O
village	O
.	O
</s>
<s>
Development	O
of	O
Ikaruga	B-Application
began	O
while	O
Treasure	O
's	O
Sin	B-Application
and	I-Application
Punishment	I-Application
(	O
2000	O
)	O
was	O
still	O
in	O
development	O
.	O
</s>
<s>
Ikaruga	B-Application
was	O
self-funded	O
(	O
and	O
later	O
self-published	O
)	O
.	O
</s>
<s>
Since	O
company	O
resources	O
were	O
allocated	O
for	O
Sin	B-Application
and	I-Application
Punishment	I-Application
,	O
director	O
Hiroshi	O
Iuchi	O
worked	O
on	O
Ikaruga	B-Application
at	O
home	O
on	O
his	O
spare	O
time	O
and	O
developed	O
a	O
prototype	B-Application
with	O
help	O
from	O
programmer	O
Atsutomo	O
Nakagawa	O
.	O
</s>
<s>
Ikaruga	B-Application
shares	O
basic	O
shooter	O
gameplay	O
elements	O
with	O
an	O
earlier	O
Treasure	O
shooter	O
,	O
Radiant	B-Application
Silvergun	I-Application
(	O
1998	O
)	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
polarity	O
elements	O
are	O
similar	O
to	O
those	O
in	O
their	O
earlier	O
game	O
Silhouette	B-Application
Mirage	I-Application
(	O
1997	O
)	O
.	O
</s>
<s>
Another	O
source	O
of	O
inspiration	O
was	O
the	O
defense	O
system	O
in	O
Shinrei	B-Application
Jusatsushi	I-Application
Taromaru	I-Application
(	O
1997	O
)	O
for	O
the	O
Sega	B-Device
Saturn	I-Device
.	O
</s>
<s>
Iuchi	O
reused	O
sprites	O
from	O
Radiant	B-Application
Silvergun	I-Application
so	O
he	O
could	O
finish	O
the	O
prototype	B-Application
quickly	O
.	O
</s>
<s>
Gameplay	O
ideas	O
in	O
the	O
prototype	B-Application
version	O
were	O
later	O
included	O
in	O
a	O
special	O
bonus	O
mode	O
in	O
the	O
final	O
game	O
.	O
</s>
<s>
Ikaruga	B-Application
has	O
been	O
described	O
as	O
a	O
spiritual	O
sequel	O
to	O
Radiant	B-Application
Silvergun	I-Application
.	O
</s>
<s>
Originally	O
,	O
Radiant	B-Application
Silvergun	I-Application
was	O
intended	O
to	O
be	O
a	O
trilogy	O
,	O
and	O
Ikaruga	B-Application
began	O
development	O
as	O
a	O
direct	O
sequel	O
,	O
codenamed	O
"	O
Project	O
RS-2	O
"	O
.	O
</s>
<s>
The	O
concept	O
theme	O
for	O
Radiant	B-Application
Silvergun	I-Application
was	O
“	O
World	O
”	O
,	O
and	O
for	O
Ikaruga	B-Application
it	O
was	O
“	O
Will	O
”	O
.	O
</s>
<s>
In	O
keeping	O
with	O
Treasure	O
's	O
game	O
design	O
philosophy	O
,	O
Ikaruga	B-Application
was	O
intentionally	O
designed	O
to	O
challenge	O
the	O
conventions	O
of	O
standard	O
game	O
design	O
and	O
develop	O
a	O
new	O
type	O
of	O
shooting	O
game	O
.	O
</s>
<s>
Unlike	O
Radiant	B-Application
Silvergun	I-Application
,	O
the	O
scoring	O
system	O
was	O
not	O
tied	O
to	O
gameplay	O
.	O
</s>
<s>
By	O
the	O
time	O
development	O
was	O
finished	O
,	O
5	O
Treasure	O
staff	O
had	O
worked	O
on	O
the	O
game	O
,	O
as	O
well	O
as	O
3	O
support	O
staff	O
from	O
G.rev	O
which	O
was	O
raising	O
funds	O
to	O
develop	O
its	O
own	O
shooter	O
,	O
Border	B-Application
Down	I-Application
(	O
2003	O
)	O
.	O
</s>
<s>
Ikaruga	B-Application
was	O
targeted	O
to	O
Treasure	O
's	O
core	O
fanbase	O
,	O
as	O
pleasing	O
them	O
was	O
the	O
team	O
's	O
first	O
priority	O
.	O
</s>
<s>
Although	O
the	O
game	O
was	O
primarily	O
being	O
developed	O
for	O
the	O
Sega	O
NAOMI	O
arcade	O
platform	O
,	O
it	O
was	O
standard	O
for	O
NAOMI	O
games	O
to	O
be	O
ported	O
to	O
the	B-Operating_System
Dreamcast	I-Operating_System
,	O
and	O
so	O
the	O
development	O
team	O
had	O
this	O
in	O
mind	O
.	O
</s>
<s>
The	O
NAOMI	O
version	O
was	O
bug	O
checked	O
on	O
a	O
Dreamcast	B-Operating_System
,	O
so	O
porting	O
was	O
very	O
easy	O
.	O
</s>
<s>
Ikaruga	B-Application
was	O
first	O
released	O
in	O
arcades	O
in	O
Japan	O
on	O
20	O
December	O
2001	O
.	O
</s>
<s>
A	O
Dreamcast	B-Operating_System
port	O
was	O
released	O
exclusively	O
in	O
Japan	O
on	O
5	O
September	O
2002	O
.	O
</s>
<s>
Although	O
not	O
yet	O
published	O
in	O
the	O
West	O
,	O
Ikaruga	B-Application
began	O
to	O
garner	O
a	O
cult	O
following	O
in	O
North	O
America	O
among	O
import	O
gamers	O
.	O
</s>
<s>
On	O
16	O
January	O
2003	O
,	O
Infogrames	O
published	O
Ikaruga	B-Application
for	O
the	O
GameCube	B-Application
in	O
Japan	O
under	O
their	O
Atari	O
label	O
.	O
</s>
<s>
Later	O
that	O
month	O
Infogrames	O
confirmed	O
the	O
GameCube	B-Application
version	O
of	O
Ikaruga	B-Application
would	O
come	O
to	O
North	O
America	O
and	O
Europe	O
,	O
with	O
Infogrames	O
representatives	O
citing	O
the	O
popularity	O
of	O
Ikaruga	B-Application
in	O
Japan	O
and	O
growing	O
fan	O
base	O
around	O
the	O
world	O
.	O
</s>
<s>
On	O
12	O
September	O
2007	O
,	O
Microsoft	O
announced	O
they	O
were	O
planning	O
on	O
releasing	O
Ikaruga	B-Application
on	O
Xbox	B-Device
Live	I-Device
Arcade	I-Device
for	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
.	O
</s>
<s>
Treasure	O
later	O
released	O
Ikaruga	B-Application
on	O
the	O
arcade	O
distribution	O
platform	O
,	O
NESiCAxLive	B-Application
,	O
on	O
8	O
August	O
2013	O
.	O
</s>
<s>
In	O
October	O
2013	O
,	O
Treasure	O
placed	O
the	O
title	O
into	O
the	O
Steam	B-Application
Greenlight	O
process	O
to	O
bring	O
the	O
game	O
(	O
based	O
on	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
version	O
)	O
to	O
Microsoft	B-Application
Windows	I-Application
,	O
with	O
hopes	O
to	O
bring	O
their	O
other	O
titles	O
to	O
the	O
platform	O
later	O
.	O
</s>
<s>
The	O
game	O
was	O
released	O
on	O
Steam	B-Application
on	O
18	O
February	O
2014	O
.	O
</s>
<s>
It	O
was	O
also	O
published	O
by	O
Nicalis	O
for	O
the	O
Nintendo	B-Application
Switch	I-Application
on	O
29	O
May	O
2018	O
,	O
supporting	O
both	O
horizontal	O
and	O
vertical	O
screen	O
orientations	O
.	O
</s>
<s>
In	O
June	O
2018	O
,	O
Ikaruga	B-Application
was	O
also	O
released	O
on	O
the	B-Operating_System
PlayStation	I-Operating_System
4	I-Operating_System
.	O
</s>
<s>
On	O
22	O
November	O
2019	O
,	O
Nicalis	O
announced	O
that	O
physical	O
copies	O
were	O
in	O
production	O
for	O
both	O
the	O
Nintendo	B-Application
Switch	I-Application
and	O
the	B-Operating_System
PlayStation	I-Operating_System
4	I-Operating_System
.	O
</s>
<s>
Initial	O
reception	O
of	O
Ikaruga	B-Application
in	O
Japan	O
was	O
mixed	O
.	O
</s>
<s>
They	O
both	O
felt	O
Ikaruga	B-Application
was	O
a	O
brand	O
new	O
type	O
of	O
shooter	O
and	O
that	O
bringing	O
variety	O
was	O
important	O
to	O
the	O
growth	O
of	O
game	O
centers	O
.	O
</s>
<s>
The	O
original	O
Dreamcast	B-Operating_System
port	O
of	O
Ikaruga	B-Application
was	O
well	O
received	O
by	O
Greg	O
Kasavin	O
of	O
GameSpot	O
.	O
</s>
<s>
He	O
also	O
praised	O
the	O
game	O
for	O
bringing	O
back	O
a	O
dead	O
genre	O
to	O
the	O
forefront	O
,	O
saying	O
"	O
Ikaruga	B-Application
takes	O
20	O
years	O
of	O
great	O
ideas	O
in	O
game	O
design	O
and	O
somehow	O
manages	O
to	O
put	O
an	O
entirely	O
new	O
spin	O
on	O
them	O
...	O
for	O
the	O
sake	O
of	O
making	O
a	O
game	O
that	O
's	O
both	O
familiar	O
and	O
utterly	O
unique.	O
"	O
</s>
<s>
The	O
GameCube	B-Application
release	O
received	O
generally	O
favorable	O
reviews	O
by	O
western	O
critics	O
.	O
</s>
<s>
Critics	O
agreed	O
that	O
Ikarugas	B-Application
game	O
design	O
was	O
"	O
innovative	O
"	O
,	O
"	O
clever	O
"	O
,	O
and	O
"	O
unique	O
"	O
.	O
</s>
<s>
IGN	O
listed	O
Ikaruga	B-Application
as	O
their	O
Game	O
of	O
the	O
Month	O
for	O
April	O
2003	O
,	O
while	O
GameSpot	O
named	O
it	O
the	O
best	O
GameCube	B-Application
title	O
of	O
that	O
month	O
.	O
</s>
<s>
Reception	O
of	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
and	O
Windows	O
ports	O
was	O
similar	O
to	O
the	O
GameCube	B-Application
version	O
.	O
</s>
<s>
Topher	O
Cantler	O
of	O
Destructoid	O
gave	O
Ikaruga	B-Application
a	O
perfect	O
score	O
and	O
dubbed	O
it	O
a	O
"	O
work	O
of	O
art	O
"	O
.	O
</s>
<s>
Although	O
most	O
critics	O
still	O
agreed	O
that	O
Ikarugas	B-Application
unique	O
game	O
design	O
was	O
a	O
positive	O
characteristic	O
,	O
Simon	O
Parkin	O
of	O
Eurogamer	O
offered	O
a	O
counterpoint	O
that	O
its	O
fresh	O
design	O
is	O
also	O
its	O
weakness	O
,	O
in	O
that	O
it	O
stifles	O
many	O
of	O
the	O
other	O
elements	O
that	O
define	O
shoot	O
'	O
em	O
ups	O
and	O
morph	O
it	O
into	O
something	O
different	O
and	O
"	O
inscrutable.	O
"	O
</s>
<s>
Ikaruga	B-Application
continues	O
to	O
be	O
one	O
of	O
the	O
most	O
revered	O
shooters	O
of	O
all	O
time	O
.	O
</s>
<s>
The	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
,	O
Windows	O
,	O
and	O
Switch	O
ports	O
have	O
received	O
positive	O
reviews	O
.	O
</s>
<s>
IGN	O
voted	O
Ikaruga	B-Application
the	O
3rd	O
greatest	O
2D	O
shooter	O
of	O
all	O
time	O
.	O
</s>
<s>
Adam	O
Smith	O
of	O
Rock	O
,	O
Paper	O
,	O
Shotgun	O
called	O
Ikaruga	B-Application
one	O
of	O
Treasure	O
's	O
greatest	O
works	O
and	O
"	O
one	O
of	O
the	O
most	O
perfect	O
games	O
 [ he ] 	O
ever	O
played.	O
"	O
</s>
<s>
The	B-Operating_System
Dreamcast	I-Operating_System
and	O
GameCube	B-Application
versions	O
sold	O
33,860	O
physical	O
units	O
in	O
Japan	O
.	O
</s>
<s>
The	O
Xbox	B-Device
Live	I-Device
Arcade	I-Device
version	O
sold	O
137,088	O
digital	O
units	O
on	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
,	O
.	O
</s>
<s>
The	O
PC	O
version	O
has	O
sold	O
128,543	O
digital	O
units	O
on	O
Steam	B-Application
,	O
.	O
</s>
