<s>
GoldSrc	B-Application
(	O
pronounced	O
"	O
gold	B-Application
source	I-Application
"	O
)	O
is	O
a	O
proprietary	B-Application
game	O
engine	O
developed	O
by	O
Valve	O
.	O
</s>
<s>
At	O
its	O
core	O
,	O
GoldSrc	B-Application
is	O
a	O
heavily	O
modified	O
version	O
of	O
id	O
Software	O
's	O
Quake	B-Application
engine	I-Application
.	O
</s>
<s>
It	O
originally	O
made	O
its	O
debut	O
in	O
1998	O
with	O
Half-Life	B-Application
,	O
and	O
would	O
power	O
future	O
games	O
developed	O
by	O
or	O
with	O
oversight	O
from	O
Valve	O
,	O
including	O
Half-Life	B-Application
expansions	O
,	O
Day	B-Application
of	I-Application
Defeat	I-Application
,	O
and	O
multiple	O
games	O
in	O
the	O
Counter-Strike	B-Application
series	I-Application
.	O
</s>
<s>
GoldSrc	B-Application
was	O
succeeded	O
by	O
the	O
Source	B-Application
engine	I-Application
with	O
the	O
releases	O
of	O
Half-Life	B-Application
:	O
Source	B-Application
,	O
Half-Life	B-Application
2	I-Application
,	O
and	O
Counter-Strike	B-Application
:	I-Application
Source	I-Application
in	O
2004	O
.	O
</s>
<s>
The	O
basis	O
of	O
GoldSrc	B-Application
is	O
the	O
engine	O
used	O
in	O
the	O
video	O
game	O
Quake	B-Application
,	O
albeit	O
with	O
heavy	O
modification	O
by	O
Valve	O
.	O
</s>
<s>
While	O
the	O
engine	O
served	O
as	O
the	O
basis	O
for	O
GoldSrc	B-Application
,	O
Gabe	O
Newell	O
has	O
stated	O
that	O
a	O
majority	O
of	O
the	O
code	O
used	O
in	O
the	O
engine	O
was	O
created	O
by	O
Valve	O
themselves	O
.	O
</s>
<s>
GoldSrc	B-Application
's	O
artificial	B-Application
intelligence	I-Application
systems	O
,	O
for	O
example	O
,	O
were	O
essentially	O
made	O
from	O
scratch.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx1	O
The	O
engine	O
also	O
reuses	O
code	O
from	O
other	O
games	O
in	O
the	O
Quake	B-Application
series	O
,	O
including	O
QuakeWorld	O
and	O
Quake	B-Application
II	I-Application
,	O
but	O
this	O
reuse	O
is	O
minimal	O
in	O
comparison	O
to	O
that	O
of	O
the	O
original	O
Quake	B-Application
.	O
</s>
<s>
In	O
1997	O
,	O
Valve	O
hired	O
Ben	O
Morris	O
and	O
acquired	O
,	O
a	O
tool	O
for	O
creating	O
custom	O
Quake	B-Application
maps	O
.	O
</s>
<s>
The	O
tool	O
was	O
later	O
renamed	O
to	O
Valve	B-Application
Hammer	I-Application
Editor	I-Application
and	O
became	O
the	O
official	O
mapping	O
tool	O
for	O
GoldSrc	B-Application
.	O
</s>
<s>
Prior	O
to	O
the	O
creation	O
of	O
the	O
Source	B-Application
engine	I-Application
,	O
the	O
GoldSrc	B-Application
engine	I-Application
had	O
no	O
real	O
title	O
and	O
was	O
simply	O
called	O
"	O
The	O
Half-Life	B-Application
engine	I-Application
"	O
.	O
</s>
<s>
When	O
the	O
need	O
arose	O
for	O
Valve	O
to	O
work	O
on	O
the	O
engine	O
without	O
risking	O
introducing	O
bugs	O
into	O
Half-Lifes	O
codebase	O
,	O
Valve	O
forked	B-Application
the	O
code	O
from	O
the	O
Half-Life	B-Application
engine	I-Application
,	O
creating	O
two	O
main	O
engine	O
branches	B-General_Concept
:	O
one	O
gold	O
master	B-General_Concept
branch	I-General_Concept
titled	O
"	O
GoldSrc	B-Application
"	O
and	O
the	O
other	O
"	O
Src	O
"	O
.	O
</s>
<s>
Internally	O
,	O
any	O
games	O
using	O
the	O
original	O
branch	O
were	O
referred	O
to	O
as	O
"	O
Goldsource	B-Application
"	O
to	O
differentiate	O
it	O
from	O
the	O
second	O
branch	O
,	O
which	O
evolved	O
into	O
the	O
Source	B-Application
engine	I-Application
.	O
</s>
<s>
Eventually	O
,	O
"	O
GoldSrc	B-Application
"	O
became	O
something	O
of	O
a	O
moniker	O
for	O
the	O
engine	O
and	O
was	O
adopted	O
as	O
the	O
official	O
title	O
externally	O
.	O
</s>
<s>
Valve	O
released	O
versions	O
of	O
the	O
GoldSrc	B-Application
engine	I-Application
for	O
OS	B-Operating_System
X	I-Operating_System
and	O
Linux	B-Application
in	O
2013	O
,	O
eventually	O
porting	O
all	O
of	O
their	O
first-party	O
games	O
using	O
the	O
engine	O
to	O
the	O
platforms	O
by	O
the	O
end	O
of	O
the	O
year	O
.	O
</s>
<s>
Half-Life	B-Application
seriesHalf-Life	O
was	O
Valve	O
's	O
debut	O
title	O
and	O
the	O
first	O
to	O
use	O
GoldSrc	B-Application
.	O
</s>
<s>
The	O
game	O
was	O
followed	O
up	O
with	O
two	O
expansions	O
,	O
Half-Life	B-Application
:	I-Application
Opposing	I-Application
Force	I-Application
and	O
Half-Life	B-Application
:	I-Application
Blue	I-Application
Shift	I-Application
,	O
both	O
of	O
which	O
ran	O
GoldSrc	B-Application
and	O
were	O
developed	O
by	O
Gearbox	O
Software	O
.	O
</s>
<s>
Half-Life	B-Application
:	I-Application
Decay	I-Application
,	O
an	O
expansion	O
pack	O
for	O
Half-Life	B-Application
only	O
released	O
on	O
PlayStation	B-Device
2	I-Device
,	O
was	O
released	O
in	O
2001	O
alongside	O
Half-Life	B-Application
debut	O
on	O
the	O
platform	O
.	O
</s>
<s>
Unlike	O
other	O
games	O
in	O
the	O
series	O
,	O
it	O
never	O
received	O
an	O
official	O
version	O
for	O
Windows	B-Application
,	O
however	O
an	O
unofficial	O
version	O
of	O
the	O
game	O
was	O
released	O
by	O
independent	O
developers	O
in	O
2008	O
.	O
</s>
<s>
Half-Life	B-Application
:	I-Application
Decay	I-Application
was	O
the	O
final	O
iteration	O
in	O
the	O
Half-Life	B-Application
series	O
to	O
run	O
on	O
GoldSrc	B-Application
,	O
with	O
all	O
future	O
entries	O
in	O
the	O
series	O
using	O
the	O
Source	B-Application
and	O
Source	B-Operating_System
2	I-Operating_System
engines	O
.	O
</s>
<s>
Valve	O
developed	O
several	O
games	O
using	O
the	O
GoldSrc	B-Application
engine	I-Application
,	O
many	O
of	O
which	O
were	O
based	O
on	O
original	O
user-made	O
modifications	O
.	O
</s>
<s>
Valve	O
's	O
Team	B-Application
Fortress	I-Application
Classic	I-Application
,	O
released	O
in	O
1999	O
,	O
was	O
developed	O
primarily	O
by	O
two	O
of	O
the	O
developers	O
of	O
the	O
Quake	B-Application
mod	O
Team	B-Application
Fortress	I-Application
.	O
</s>
<s>
Counter-Strike	B-Application
and	O
Day	B-Application
of	I-Application
Defeat	I-Application
were	O
also	O
originally	O
Half-Life	B-Application
modifications	O
that	O
Valve	O
purchased	O
the	O
rights	O
to	O
and	O
re-released	O
as	O
standalone	O
titles	O
.	O
</s>
<s>
Counter-Strike	B-Application
evolved	O
into	O
its	O
own	O
series	O
with	O
the	O
debut	O
of	O
the	O
Japanese	O
arcade	O
game	O
Counter-Strike	B-Application
Neo	O
in	O
2003	O
and	O
Valve	O
's	O
own	O
follow-up	O
in	O
2004	O
,	O
Counter-Strike	B-Application
:	I-Application
Condition	I-Application
Zero	I-Application
,	O
both	O
of	O
which	O
run	O
on	O
the	O
GoldSrc	B-Application
engine	I-Application
.	O
</s>
<s>
Although	O
Valve	O
's	O
further	O
installments	O
in	O
the	O
series	O
starting	O
with	O
Counter-Strike	B-Application
:	I-Application
Source	I-Application
use	O
the	O
newer	O
Source	B-Application
engine	I-Application
instead	O
,	O
Counter-Strike	B-Application
Online	I-Application
and	O
Counter-Strike	B-Application
Nexon	O
:	O
Zombies	O
,	O
two	O
spinoff	O
titles	O
released	O
by	O
Nexon	O
in	O
2008	O
and	O
2014	O
respectively	O
,	O
use	O
GoldSrc	B-Application
as	O
their	O
basis	O
.	O
</s>
<s>
The	O
GoldSrc	B-Application
engine	I-Application
was	O
also	O
used	O
for	O
a	O
variety	O
of	O
third-party	O
games	O
and	O
modifications	O
not	O
directly	O
developed	O
by	O
Valve	O
.	O
</s>
<s>
Rewolf	O
Software	O
used	O
the	O
engine	O
for	O
the	O
game	O
Gunman	B-Application
Chronicles	I-Application
in	O
2000	O
,	O
and	O
the	O
PC	O
version	O
of	O
James	B-Application
Bond	I-Application
007	I-Application
:	I-Application
Nightfire	I-Application
was	O
developed	O
by	O
Gearbox	O
Software	O
using	O
a	O
modified	O
version	O
of	O
GoldSrc	B-Application
in	O
2002	O
.	O
</s>
<s>
Unofficial	O
,	O
community-made	O
modifications	O
of	O
GoldSrc	B-Application
have	O
also	O
been	O
produced	O
.	O
</s>
<s>
Notable	O
games	O
include	O
Natural	B-Application
Selection	I-Application
,	O
Cry	B-Application
of	I-Application
Fear	I-Application
and	O
Sven	B-Application
Co-op	I-Application
,	O
with	O
Valve	O
's	O
Team	B-Application
Fortress	I-Application
Classic	I-Application
,	O
Counter-Strike	B-Application
,	O
and	O
Day	B-Application
of	I-Application
Defeat	I-Application
all	O
being	O
based	O
on	O
GoldSrc	B-Application
mods	O
of	O
the	O
same	O
names	O
.	O
</s>
<s>
Cry	B-Application
of	I-Application
Fear	I-Application
and	O
Sven	B-Application
Co-op	I-Application
''	O
have	O
since	O
been	O
released	O
for	O
free	O
as	O
standalone	O
games	O
on	O
Steam	B-Application
,	O
both	O
of	O
which	O
use	O
a	O
licensed	O
derivative	O
of	O
the	O
engine	O
with	O
their	O
own	O
customizations	O
.	O
</s>
