<s>
Half-Life	B-Application
:	I-Application
Opposing	I-Application
Force	I-Application
is	O
an	O
expansion	O
pack	O
for	O
the	O
first-person	O
shooter	O
game	O
Half-Life	B-Application
.	O
</s>
<s>
Opposing	O
Force	O
was	O
the	O
first	O
expansion	O
for	O
Half-Life	B-Application
and	O
was	O
announced	O
in	O
April	O
1999	O
.	O
</s>
<s>
Lead	O
designer	O
Randy	O
Pitchford	O
noted	O
that	O
he	O
believed	O
Gearbox	O
was	O
selected	O
to	O
develop	O
Opposing	O
Force	O
because	O
Valve	O
,	O
the	O
creators	O
of	O
Half-Life	B-Application
,	O
wanted	O
to	O
concentrate	O
on	O
their	O
future	O
projects	O
.	O
</s>
<s>
Opposing	O
Force	O
returns	O
to	O
the	O
same	O
setting	O
as	O
Half-Life	B-Application
,	O
but	O
instead	O
portrays	O
the	O
events	O
from	O
the	O
perspective	O
of	O
a	O
U.S.	O
Marine	O
,	O
one	O
of	O
the	O
enemy	O
characters	O
in	O
the	O
original	O
game	O
.	O
</s>
<s>
Opposing	O
Force	O
was	O
received	O
well	O
by	O
critics	O
,	O
with	O
many	O
describing	O
it	O
as	O
the	O
new	O
benchmark	O
title	O
for	O
expansion	O
packs	O
,	O
in	O
a	O
similar	O
fashion	O
to	O
how	O
Half-Life	B-Application
revolutionized	O
the	O
first-person	O
shooter	O
genre	O
.	O
</s>
<s>
As	O
an	O
expansion	O
pack	O
for	O
Half-Life	B-Application
,	O
Opposing	O
Force	O
is	O
a	O
first-person	O
shooter	O
.	O
</s>
<s>
The	O
overall	O
gameplay	O
of	O
Opposing	O
Force	O
does	O
not	O
significantly	O
differ	O
from	O
that	O
of	O
Half-Life	B-Application
.	O
</s>
<s>
Opposing	O
Force	O
also	O
features	O
an	O
extended	O
multiplayer	O
,	O
incorporating	O
the	O
various	O
new	O
environments	O
and	O
weapons	O
into	O
the	O
original	O
deathmatch	O
mode	O
used	O
in	O
Half-Life	B-Application
.	O
</s>
<s>
After	O
release	O
,	O
a	O
new	O
capture	B-Application
the	I-Application
flag	I-Application
mode	O
with	O
additional	O
levels	O
,	O
items	O
and	O
powerups	B-Operating_System
,	O
was	O
created	O
by	O
Gearbox	O
.	O
</s>
<s>
Three	O
types	O
of	O
Marines	O
are	O
featured	O
in	O
the	O
game	O
:	O
the	O
soldier	O
will	O
simply	O
provide	O
fire	O
support	O
for	O
the	O
player	O
with	O
a	O
submachine	O
gun	O
,	O
shotgun	O
or	O
machine	O
gun	O
,	O
the	O
combat	O
medic	O
is	O
capable	O
of	O
healing	O
the	O
player	O
and	O
other	O
non-player	O
characters	O
,	O
while	O
the	O
engineer	B-Language
can	O
cut	O
through	O
doors	O
and	O
remove	O
obstacles	O
,	O
allowing	O
the	O
player	O
and	O
their	O
squad	O
to	O
proceed	O
unhindered	O
.	O
</s>
<s>
A	O
selection	O
of	O
enemies	O
from	O
Half-Life	B-Application
populate	O
the	O
game	O
,	O
including	O
alien	O
creatures	O
such	O
as	O
headcrabs	O
and	O
Vortigaunts	O
.	O
</s>
<s>
Opposing	O
Force	O
is	O
set	O
in	O
the	O
same	O
location	O
and	O
timeframe	O
as	O
that	O
of	O
Half-Life	B-Application
,	O
taking	O
place	O
at	O
a	O
remote	O
New	O
Mexico	O
laboratory	O
called	O
the	O
Black	O
Mesa	O
Research	O
Facility	O
.	O
</s>
<s>
In	O
Half-Life	B-Application
,	O
the	O
player	O
takes	O
on	O
the	O
role	O
of	O
Gordon	O
Freeman	O
,	O
a	O
scientist	O
involved	O
in	O
an	O
accident	O
that	O
opens	O
an	O
inter-dimensional	O
portal	O
to	O
the	O
borderworld	O
of	O
Xen	O
,	O
allowing	O
the	O
alien	O
creatures	O
of	O
Xen	O
to	O
attack	O
the	O
facility	O
.	O
</s>
<s>
Opposing	O
Force	O
,	O
however	O
,	O
shows	O
the	O
events	O
of	O
Half-Life	B-Application
from	O
the	O
perspective	O
of	O
a	O
different	O
protagonist	O
.	O
</s>
<s>
Shephard	O
makes	O
it	O
to	O
the	O
Lambda	O
Complex	O
alive	O
,	O
and	O
briefly	O
sees	O
Gordon	O
Freeman	O
as	O
the	O
latter	O
teleports	B-General_Concept
to	O
Xen	O
in	O
the	O
final	O
stages	O
of	O
Half-Life	B-Application
.	O
</s>
<s>
To	O
escape	O
the	O
teleportation	B-General_Concept
chamber	O
,	O
Shephard	O
is	O
forced	O
to	O
enter	O
a	O
separate	O
portal	O
,	O
briefly	O
taking	O
him	O
to	O
Xen	O
before	O
depositing	O
him	O
in	O
an	O
entirely	O
different	O
area	O
of	O
the	O
facility	O
.	O
</s>
<s>
Half-Life	B-Application
:	I-Application
Opposing	I-Application
Force	I-Application
was	O
announced	O
by	O
developer	O
Gearbox	O
Software	O
on	O
April	O
15	O
,	O
1999	O
.	O
</s>
<s>
In	O
their	O
press	O
release	O
,	O
founder	O
Randy	O
Pitchford	O
stated	O
that	O
"	O
our	O
number	O
one	O
goal	O
is	O
to	O
preserve	O
the	O
integrity	O
of	O
Half-Life	B-Application
and	O
provide	O
new	O
experiences	O
that	O
expand	O
upon	O
the	O
sensation	O
of	O
the	O
original	O
"	O
.	O
</s>
<s>
In	O
a	O
later	O
interview	O
,	O
Pitchford	O
stated	O
that	O
he	O
believed	O
that	O
Valve	O
offered	O
Gearbox	O
the	O
chance	O
to	O
make	O
a	O
Half-Life	B-Application
expansion	O
was	O
from	O
a	O
wish	O
"	O
to	O
focus	O
on	O
their	O
future	O
titles	O
"	O
.	O
</s>
<s>
In	O
addition	O
,	O
Pitchford	O
commented	O
that	O
Valve	O
and	O
Gearbox	O
had	O
agreed	O
not	O
to	O
"	O
severely	O
modify	O
"	O
the	O
game	O
engine	O
used	O
by	O
Half-Life	B-Application
and	O
Opposing	O
Force	O
as	O
it	O
"	O
risks	O
breaking	O
all	O
of	O
the	O
wonderful	O
work	O
"	O
that	O
the	O
game	O
's	O
custom	O
content	O
community	O
was	O
creating	O
.	O
</s>
<s>
Several	O
other	O
designers	O
subsequently	O
joined	O
the	O
project	O
in	O
September	O
1999	O
,	O
with	O
collective	O
experience	O
from	O
the	O
development	O
of	O
Daikatana	B-Application
,	O
Quake	B-Application
II	I-Application
,	O
Doom	B-Application
and	O
Shadow	B-Application
Warrior	I-Application
.	O
</s>
<s>
Gearbox	O
later	O
released	O
a	O
multiplayer	O
update	O
in	O
May	O
2000	O
,	O
adding	O
a	O
capture	B-Application
the	I-Application
flag	I-Application
mode	O
,	O
along	O
with	O
various	O
items	O
to	O
accompany	O
the	O
new	O
mode	O
.	O
</s>
<s>
Opposing	O
Force	O
was	O
later	O
released	O
on	O
Valve	O
's	O
Steam	B-Application
content	I-Application
delivery	I-Application
system	O
.	O
</s>
<s>
Opposing	O
Force	O
was	O
published	O
as	O
part	O
of	O
Sierra	O
's	O
Half-Life	B-Application
:	O
Generation	O
compilation	O
in	O
2002	O
,	O
<ref>{{cite web|url=Half-Life: Generation|publisher=MobyGames|access-date=April 1, 2016}}</ref>	O
and	O
as	O
part	O
of	O
Valve	O
and	O
Electronic	O
Arts	O
 '	O
Half	B-Application
Life	I-Application
1	I-Application
:	O
Anthology	O
on	O
September	O
26	O
,	O
2005	O
.	O
</s>
<s>
Although	O
figures	O
for	O
sales	O
on	O
Steam	B-Application
have	O
not	O
been	O
released	O
,	O
Opposing	O
Force	O
eventually	O
sold	O
over	O
1.1	O
million	O
copies	O
at	O
retail.Computer	O
and	O
Video	O
Games	O
reviewer	O
Kim	O
Randell	O
noted	O
that	O
"	O
Gearbox	O
has	O
obviously	O
gone	O
to	O
great	O
pains	O
to	O
provide	O
a	O
similar	O
experience	O
to	O
the	O
original	O
"	O
.	O
</s>
<s>
Erik	O
Wolpaw	O
,	O
writing	O
for	O
GameSpot	O
,	O
noted	O
that	O
as	O
most	O
expansion	O
packs	O
were	O
mediocre	O
,	O
"	O
it	O
's	O
appropriate	O
that	O
Gearbox	O
Software	O
's	O
Opposing	O
Force	O
,	O
the	O
official	O
expansion	O
for	O
the	O
genre-redefining	O
Half-Life	B-Application
,	O
in	O
turn	O
sets	O
a	O
new	O
standard	O
of	O
quality	O
for	O
future	O
action-game	O
mission	O
packs	O
"	O
.	O
</s>
<s>
Although	O
criticizing	O
some	O
elements	O
of	O
the	O
artificial	B-Application
intelligence	I-Application
and	O
describing	O
some	O
of	O
the	O
new	O
models	O
as	O
"	O
merely	O
window	O
dressing	O
"	O
,	O
the	O
review	O
concluded	O
that	O
Opposing	O
Force	O
was	O
an	O
"	O
impassioned	O
application	O
of	O
creative	O
design	O
"	O
.GamePro	O
stated	O
that	O
"	O
Gearbox	O
has	O
done	O
one	O
hell	O
of	O
a	O
job	O
in	O
creating	O
not	O
just	O
an	O
add-on	O
for	O
Half-Life	B-Application
,	O
but	O
a	O
continuation	O
of	O
a	O
masterpiece	O
"	O
,	O
praising	O
both	O
level	O
design	O
and	O
story	O
elements	O
,	O
but	O
noted	O
that	O
it	O
was	O
a	O
little	O
too	O
short	O
.	O
</s>
<s>
However	O
,	O
some	O
critics	O
dissented	O
on	O
the	O
idea	O
that	O
Opposing	O
Force	O
was	O
as	O
influential	O
as	O
other	O
reviewers	O
made	O
out.PC	O
Zone	O
stated	O
that	O
"	O
the	O
taste	O
left	O
in	O
the	O
mouth	O
is	O
a	O
bitter	O
one	O
"	O
,	O
noting	O
that	O
"	O
Opposing	O
Force	O
is	O
a	O
few	O
excellent	O
ideas	O
strung	O
together	O
by	O
pedestrian	O
Half-Life	B-Application
padding	O
"	O
,	O
but	O
concluded	O
that	O
"	O
it	O
was	O
still	O
a	O
good	O
weekend	O
's	O
worth	O
of	O
entertainment	O
"	O
.	O
</s>
<s>
The	O
editors	O
of	O
PC	O
Gamer	O
US	O
presented	O
Opposing	O
Force	O
with	O
their	O
1999	O
"	O
Best	O
Expansion	O
Pack	O
"	O
award	O
,	O
and	O
nominated	O
it	O
as	O
1999	O
's	O
overall	O
best	O
game	O
of	O
the	O
year	O
,	O
although	O
it	O
lost	O
the	O
latter	O
prize	O
to	O
Homeworld	B-Application
.	O
</s>
