<s>
Half-Life	B-Application
:	I-Application
Decay	I-Application
is	O
a	O
multiplayer-only	O
expansion	O
pack	O
for	O
Valve	O
's	O
first-person	O
shooter	O
Half-Life	B-Application
.	O
</s>
<s>
Developed	O
by	O
Gearbox	O
Software	O
and	O
published	O
by	O
Sierra	O
On-Line	O
,	O
Decay	O
was	O
released	O
as	O
part	O
of	O
the	O
PlayStation	B-Device
2	I-Device
version	O
of	O
Half-Life	B-Application
in	O
2001	O
.	O
</s>
<s>
It	O
is	O
the	O
third	O
expansion	O
pack	O
for	O
Half-Life	B-Application
,	O
and	O
like	O
its	O
predecessors	O
,	O
Decay	O
returns	O
to	O
the	O
setting	O
and	O
timeline	O
of	O
the	O
original	O
story	O
,	O
albeit	O
portraying	O
the	O
story	O
from	O
the	O
viewpoint	O
of	O
a	O
different	O
set	O
of	O
protagonists	O
:	O
two	O
female	O
scientists	O
working	O
in	O
the	O
Black	O
Mesa	O
Research	O
Facility	O
.	O
</s>
<s>
A	O
number	O
of	O
reviews	O
stated	O
that	O
the	O
game	O
simply	O
felt	O
like	O
little	O
more	O
than	O
an	O
extra	O
add-on	O
for	O
the	O
PlayStation	B-Device
2	I-Device
version	O
of	O
Half-Life	B-Application
.	O
</s>
<s>
As	O
is	O
the	O
case	O
with	O
the	O
other	O
games	O
in	O
the	O
Half-Life	B-Application
series	O
,	O
Decay	O
is	O
a	O
first-person	O
shooter	O
.	O
</s>
<s>
However	O
,	O
Decay	O
differs	O
from	O
Half-Life	B-Application
and	O
its	O
first	O
two	O
expansion	O
packs	O
,	O
Opposing	B-Application
Force	I-Application
and	O
Blue	B-Application
Shift	I-Application
,	O
in	O
that	O
it	O
is	O
designed	O
for	O
cooperative	O
multiplayer	O
gameplay	O
.	O
</s>
<s>
When	O
not	O
in	O
use	O
,	O
a	O
character	O
has	O
sufficient	O
artificial	B-Application
intelligence	I-Application
to	O
defend	O
themselves	O
,	O
but	O
otherwise	O
does	O
not	O
move	O
from	O
where	O
they	O
have	O
been	O
left	O
by	O
the	O
player	O
.	O
</s>
<s>
In	O
Half-Life	B-Application
,	O
players	O
usually	O
fight	O
alone	O
and	O
only	O
occasionally	O
encounter	O
friendly	O
non-player	O
characters	O
who	O
assist	O
them	O
,	O
such	O
as	O
security	O
guards	O
and	O
scientists	O
.	O
</s>
<s>
An	O
array	O
of	O
enemy	O
characters	O
from	O
Half-Life	B-Application
populate	O
the	O
game	O
,	O
including	O
alien	O
lifeforms	O
such	O
as	O
headcrabs	O
and	O
Vortigaunts	O
,	O
as	O
well	O
as	O
human	O
soldiers	O
sent	O
in	O
to	O
contain	O
the	O
alien	O
threat	O
.	O
</s>
<s>
Although	O
developed	O
after	O
Opposing	B-Application
Force	I-Application
,	O
no	O
non-player	O
characters	O
or	O
weapons	O
from	O
the	O
earlier	O
expansion	O
appear	O
in	O
Decay	O
.	O
</s>
<s>
The	O
game	O
is	O
unique	O
in	O
the	O
context	O
of	O
the	O
Half-Life	B-Application
series	O
in	O
that	O
it	O
is	O
the	O
only	O
game	O
divided	O
into	O
separate	O
missions	O
,	O
each	O
with	O
a	O
specific	O
objective	O
to	O
pursue	O
,	O
instead	O
of	O
consisting	O
of	O
a	O
single	O
unbroken	O
narrative	O
.	O
</s>
<s>
Should	O
players	O
successfully	O
complete	O
the	O
game	O
's	O
nine	O
missions	O
with	O
"	O
A	O
"	O
grades	O
on	O
every	O
level	O
,	O
they	O
are	O
given	O
access	O
to	O
a	O
bonus	O
cooperative	O
mission	O
,	O
in	O
which	O
they	O
can	O
play	O
as	O
a	O
pair	O
of	O
Vortigaunts	O
,	O
as	O
well	O
as	O
the	O
ability	O
to	O
play	O
through	O
the	O
PlayStation	B-Device
2	I-Device
version	O
of	O
the	O
original	O
Half-Life	B-Application
as	O
a	O
Vortigaunt	O
.	O
</s>
<s>
Decay	O
is	O
set	O
in	O
the	O
same	O
location	O
and	O
timeframe	O
as	O
Half-Life	B-Application
.	O
</s>
<s>
Half-Life	B-Application
takes	O
place	O
at	O
a	O
laboratory	O
called	O
the	O
Black	O
Mesa	O
Research	O
Facility	O
,	O
situated	O
in	O
a	O
remote	O
desert	O
in	O
New	O
Mexico	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>
Like	O
the	O
previous	O
expansions	O
,	O
Decay	O
shows	O
the	O
story	O
of	O
Half-Life	B-Application
from	O
the	O
perspective	O
of	O
a	O
different	O
set	O
of	O
protagonists	O
.	O
</s>
<s>
In	O
Decay	O
,	O
players	O
assume	O
the	O
roles	O
of	O
Colette	O
Green	O
and	O
Gina	O
Cross	O
,	O
two	O
doctors	O
who	O
work	O
in	O
the	O
same	O
labs	O
as	O
Freeman	O
,	O
analyzing	O
anomalous	B-Application
materials	I-Application
and	O
specimens	O
retrieved	O
from	O
Xen	O
in	O
prior	O
teleportation	B-General_Concept
experiments	O
.	O
</s>
<s>
Decay	O
begins	O
with	O
Gina	O
Cross	O
and	O
Colette	O
Green	O
arriving	O
at	O
the	O
Anomalous	B-Application
Materials	I-Application
Labs	O
at	O
Black	O
Mesa	O
and	O
reporting	O
to	O
Dr.	O
Keller	O
,	O
who	O
is	O
readying	O
the	O
day	O
's	O
analysis	O
of	O
an	O
unknown	O
specimen	O
.	O
</s>
<s>
The	O
satellite	O
,	O
which	O
is	O
launched	O
by	O
Freeman	O
in	O
Half-Life	B-Application
,	O
is	O
used	O
in	O
tandem	O
with	O
ground-based	O
equipment	O
to	O
significantly	O
weaken	O
the	O
effects	O
of	O
the	O
resonance	O
cascade	O
.	O
</s>
<s>
The	O
unlockable	O
vortigaunt	O
mission	O
provides	O
background	O
information	O
explaining	O
how	O
the	O
orange	O
crystals	O
used	O
by	O
the	O
rift-sealing	O
machine	O
in	O
Half	B-Application
Life	I-Application
:	I-Application
Decay	I-Application
are	O
acquired	O
and	O
used	O
by	O
the	O
Nihilanth	O
during	O
the	O
final	O
boss	O
battle	O
in	O
Half	B-Application
Life	I-Application
.	O
</s>
<s>
A	O
cooperative	O
Half-Life	B-Application
game	O
was	O
first	O
alluded	O
to	O
by	O
publisher	O
Sierra	O
On-Line	O
in	O
November	O
2000	O
with	O
the	O
announcement	O
of	O
a	O
PlayStation	B-Device
2	I-Device
version	O
of	O
Half-Life	B-Application
.	O
</s>
<s>
At	O
the	O
time	O
,	O
however	O
,	O
it	O
was	O
unclear	O
how	O
a	O
cooperative	O
version	O
of	O
Half-Life	B-Application
would	O
be	O
implemented	O
;	O
the	O
developers	O
,	O
Gearbox	O
Software	O
,	O
were	O
still	O
experimenting	O
with	O
finding	O
the	O
most	O
balanced	O
number	O
of	O
players	O
to	O
build	O
a	O
cooperative	O
game	O
around	O
.	O
</s>
<s>
By	O
E3	O
2001	O
,	O
the	O
game	O
had	O
acquired	O
the	O
title	O
Decay	O
,	O
named	O
after	O
the	O
scientific	O
concept	O
of	O
exponential	O
decay	O
for	O
consistency	O
with	O
the	O
scientific	O
names	O
used	O
by	O
previous	O
Half-Life	B-Application
titles	O
.	O
</s>
<s>
While	O
the	O
E3	O
convention	O
only	O
provided	O
a	O
demonstration	O
of	O
the	O
main	O
Half-Life	B-Application
PlayStation	B-Device
2	I-Device
game	O
,	O
further	O
details	O
were	O
released	O
relating	O
to	O
Decays	O
premise	O
and	O
story	O
,	O
as	O
well	O
as	O
confirming	O
that	O
the	O
cooperative	O
mode	O
was	O
to	O
be	O
designed	O
for	O
two	O
players	O
.	O
</s>
<s>
These	O
new	O
models	O
were	O
updated	O
versions	O
of	O
Gearbox	O
's	O
High	O
Definition	O
pack	O
for	O
Blue	B-Application
Shift	I-Application
,	O
featuring	O
higher	O
numbers	O
of	O
polygons	B-General_Concept
and	O
animation	O
features	O
such	O
as	O
facial	O
expressions	O
.	O
</s>
<s>
The	O
enhanced	O
models	O
were	O
around	O
twice	O
as	O
detailed	O
as	O
those	O
in	O
the	O
High	O
Definition	O
pack	O
,	O
which	O
itself	O
was	O
of	O
a	O
much	O
higher	O
quality	O
than	O
the	O
original	O
models	O
in	O
Half-Life	B-Application
.	O
</s>
<s>
On	O
August	O
18	O
,	O
2001	O
,	O
Sierra	O
announced	O
that	O
Decay	O
was	O
nearly	O
complete	O
,	O
and	O
would	O
be	O
submitted	O
to	O
PlayStation	B-Device
2	I-Device
manufacturer	O
Sony	O
for	O
verification	O
within	O
days	O
.	O
</s>
<s>
The	O
entire	O
Half-Life	B-Application
for	O
PlayStation	B-Device
2	I-Device
package	O
achieved	O
gold	O
status	O
on	O
October	O
30	O
,	O
2001	O
,	O
and	O
the	O
game	O
was	O
released	O
on	O
November	O
14	O
,	O
2001	O
.	O
</s>
<s>
In	O
October	O
2005	O
,	O
work	O
was	O
begun	O
by	O
a	O
group	O
of	O
Ukrainian	O
developers	O
to	O
port	O
Decay	O
over	O
to	O
Windows	B-Application
,	O
as	O
a	O
modification	O
for	O
both	O
the	O
old	O
World	O
Opponent	O
Network	O
and	O
current	O
Steam	B-Application
versions	O
of	O
Half-Life	B-Application
.	O
</s>
<s>
The	O
port	O
relied	O
on	O
the	O
discovery	O
of	O
a	O
method	O
that	O
allowed	O
Decays	O
PS2	B-Device
game	O
files	O
to	O
be	O
converted	O
to	O
Windows	B-Application
version	O
of	O
the	O
game	O
.	O
</s>
<s>
The	O
port	O
was	O
received	O
well	O
by	O
the	O
journalists	O
in	O
the	O
industry	O
;	O
GameSpy	O
site	O
Planet	O
Half-Life	B-Application
noted	O
that	O
it	O
was	O
a	O
shame	O
that	O
an	O
official	O
PC	O
version	O
of	O
Decay	O
never	O
emerged	O
,	O
while	O
British	O
journalist	O
Alec	O
Meer	O
stated	O
that	O
it	O
was	O
"	O
fantastic	O
to	O
have	O
this	O
short	O
but	O
sweet	O
lost	O
Half-Life	B-Application
episode	O
on	O
PC	O
at	O
last	O
,	O
and	O
it	O
even	O
has	O
something	O
the	O
PS2	B-Device
version	O
didn't—online	O
play	O
"	O
.	O
</s>
<s>
Allgame	O
described	O
Decay	O
as	O
an	O
"	O
added	O
bonus	O
"	O
for	O
the	O
PlayStation	B-Device
2	I-Device
version	O
of	O
Half-Life	B-Application
,	O
but	O
noted	O
that	O
as	O
the	O
game	O
was	O
designed	O
for	O
two	O
players	O
,	O
it	O
significantly	O
suffered	O
when	O
a	O
single	O
player	O
attempts	O
to	O
play	O
it	O
by	O
switching	O
between	O
two	O
characters	O
,	O
a	O
point	O
that	O
both	O
GameSpy	O
and	O
GameSpot	O
agreed	O
on	O
.	O
</s>
<s>
While	O
The	O
Electric	O
Playground	O
reviewer	O
Steve	O
Smith	O
stated	O
that	O
the	O
control	O
scheme	O
for	O
the	O
PlayStation	B-Device
2	I-Device
version	O
of	O
Half-Life	B-Application
"	O
is	O
about	O
the	O
best	O
we	O
have	O
seen	O
on	O
the	O
PS2	B-Device
or	O
any	O
console	O
"	O
,	O
he	O
concluded	O
that	O
although	O
Decay	O
was	O
a	O
"	O
nice	O
add-on	O
"	O
,	O
it	O
was	O
"	O
no	O
reason	O
to	O
buy	O
this	O
port	O
"	O
.	O
</s>
