<s>
Operation	B-Application
C	I-Application
(	O
released	O
as	O
in	O
Japan	O
and	O
as	O
Probotector	B-Application
in	O
the	O
PAL	O
region	O
)	O
is	O
a	O
1991	O
run	O
and	O
gun	O
video	O
game	O
by	O
Konami	O
released	O
for	O
the	O
Game	B-Device
Boy	I-Device
.	O
</s>
<s>
It	O
is	O
a	O
sequel	O
to	O
Super	B-Application
Contra	I-Application
,	O
and	O
the	O
first	O
portable	O
installment	O
in	O
the	O
Contra	B-Application
series	I-Application
.	O
</s>
<s>
Operation	B-Application
C	I-Application
features	O
gameplay	O
and	O
graphics	O
similar	O
to	O
the	O
Nintendo	O
Entertainment	O
System	O
versions	O
of	O
Contra	B-Application
and	O
Super	B-Application
Contra	I-Application
.	O
</s>
<s>
The	O
game	O
has	O
a	O
total	O
of	O
five	O
stages	O
,	O
many	O
of	O
which	O
share	O
design	O
similarities	O
to	O
Super	B-Application
C	I-Application
(	O
the	O
NES	O
version	O
of	O
Super	B-Application
Contra	I-Application
)	O
.	O
</s>
<s>
The	O
soundtrack	O
consists	O
primarily	O
of	O
arranged	O
background	O
music	O
from	O
the	O
original	O
Contra	B-Application
,	O
with	O
the	O
exception	O
of	O
a	O
few	O
tunes	O
(	O
namely	O
the	O
Area	O
2	O
theme	O
,	O
the	O
Stage	O
Select	O
theme	O
,	O
the	O
sub-boss	O
theme	O
in	O
Area	O
3	O
,	O
and	O
the	O
ending	O
theme	O
)	O
.	O
</s>
<s>
Operation	B-Application
C	I-Application
was	O
the	O
first	O
Contra	B-Application
game	O
to	O
feature	O
auto-fire	O
as	O
a	O
default	O
feature	O
,	O
resulting	O
in	O
the	O
removal	O
of	O
the	O
Machine	O
Gun	O
power-up	O
from	O
previous	O
games	O
.	O
</s>
<s>
The	O
Laser	O
Rifle	O
is	O
also	O
removed	O
,	O
leaving	O
only	O
the	O
Spread	O
Shot	O
and	O
Fire	O
Gun	O
from	O
Super	B-Application
C	I-Application
.	O
However	O
,	O
the	O
game	O
introduces	O
a	O
new	O
Homing	O
Gun	O
that	O
fires	O
bullets	O
that	O
chase	O
after	O
enemies	O
.	O
</s>
<s>
Unlike	O
Super	B-Application
C	I-Application
,	O
the	O
Fire	O
Gun	O
does	O
not	O
have	O
chargeable	O
shots	O
,	O
while	O
the	O
Barrier	O
and	O
Rapid	O
Bullets	O
power-ups	O
are	O
not	O
featured	O
in	O
this	O
installment	O
either	O
.	O
</s>
<s>
The	O
player	O
takes	O
the	O
role	O
of	O
Bill	B-Application
Rizer	I-Application
,	O
who	O
must	O
neutralize	O
an	O
enemy	O
force	O
that	O
is	O
secretly	O
storing	O
an	O
alien	O
cell	O
in	O
their	O
base	O
.	O
</s>
<s>
As	O
with	O
the	O
previous	O
Contra	B-Application
games	O
for	O
the	O
NES	O
,	O
the	O
exact	O
details	O
of	O
the	O
game	O
's	O
settings	O
varies	O
between	O
supplemental	O
materials	O
:	O
in	O
the	O
Japanese	O
version	O
,	O
the	O
enemies	O
are	O
identified	O
as	O
the	O
army	O
of	O
an	O
unnamed	O
hostile	O
nation	O
that	O
is	O
seeking	O
to	O
use	O
an	O
alien	O
cell	O
to	O
produce	O
weapons	O
;	O
in	O
the	O
American	O
version	O
,	O
the	O
enemies	O
are	O
working	O
for	O
an	O
alien	O
entity	O
calling	O
itself	O
"	O
Black	O
Viper	O
"	O
.	O
</s>
<s>
The	O
Japanese	O
version	O
,	O
simply	O
titled	O
Contra	B-Application
,	O
allows	O
the	O
player	O
to	O
begin	O
the	O
game	O
at	O
any	O
of	O
the	O
first	O
four	O
stages	O
.	O
</s>
<s>
The	O
European	O
version	O
,	O
Probotector	B-Application
,	O
changed	O
the	O
main	O
character	O
and	O
some	O
of	O
the	O
enemies	O
into	O
robots	O
,	O
much	O
like	O
the	O
European	O
localizations	O
of	O
the	O
NES	O
installments	O
.	O
</s>
<s>
Operation	B-Application
C	I-Application
is	O
included	O
in	O
the	O
Game	B-Device
Boy	I-Device
compilation	O
Konami	O
GB	O
Collection	O
Vol	O
.	O
</s>
<s>
The	O
Japanese	O
version	O
is	O
identical	O
to	O
the	O
original	O
release	O
,	O
but	O
with	O
added	O
Super	B-Device
Game	I-Device
Boy	I-Device
border	O
support	O
.	O
</s>
<s>
While	O
the	O
version	O
of	O
the	O
game	O
included	O
with	O
the	O
European	O
compilation	O
is	O
titled	O
Probotector	B-Application
,	O
it	O
retains	O
the	O
original	O
human	O
characters	O
from	O
the	O
Japanese	O
release	O
and	O
adds	O
full	O
Game	B-Device
Boy	I-Device
Color	I-Device
support	O
.	O
</s>
<s>
The	O
game	O
is	O
included	O
in	O
the	O
2019	O
Contra	B-Application
Anniversary	O
Collection	O
for	O
PlayStation	B-Operating_System
4	I-Operating_System
,	O
Xbox	B-Device
One	I-Device
,	O
Nintendo	B-Application
Switch	I-Application
,	O
and	O
Steam	B-Application
.	O
</s>
<s>
Nintendo	O
Life	O
gave	O
the	O
game	O
an	O
8/10	O
score	O
,	O
praising	O
the	O
gameplay	O
,	O
controls	O
,	O
enemies	O
,	O
weapons	O
and	O
music	O
,	O
while	O
suggesting	O
that	O
the	O
game	O
borrowed	O
from	O
Super	B-Application
C	I-Application
a	O
bit	O
too	O
much	O
.	O
</s>
