<s>
Doom	B-Application
is	I-Application
a	O
1993	O
first-person	O
shooter	O
(	O
FPS	O
)	O
game	O
developed	O
by	O
id	O
Software	O
for	O
MS-DOS	B-Application
.	O
</s>
<s>
Players	O
assume	O
the	O
role	O
of	O
a	O
space	B-Application
marine	I-Application
,	O
popularly	O
known	O
as	O
Doomguy	O
,	O
fighting	O
their	O
way	O
through	O
hordes	O
of	O
invading	O
demons	B-Operating_System
from	O
hell	O
.	O
</s>
<s>
Id	O
began	O
developing	O
Doom	B-Application
after	O
the	O
release	O
of	O
their	O
previous	O
FPS	O
,	O
Wolfenstein	B-Application
3D	I-Application
(	O
1992	O
)	O
.	O
</s>
<s>
The	O
first	O
episode	O
,	O
comprising	O
nine	O
levels	O
,	O
was	O
distributed	O
freely	O
as	O
shareware	B-License
;	O
the	O
full	O
game	O
,	O
with	O
two	O
further	O
episodes	O
,	O
was	O
sold	O
via	O
mail	O
order	O
.	O
</s>
<s>
An	O
updated	O
version	O
with	O
an	O
additional	O
episode	O
and	O
more	O
difficult	O
levels	O
,	O
The	O
Ultimate	B-Application
Doom	I-Application
,	O
was	O
released	O
in	O
1995	O
and	O
sold	O
at	O
retail	O
.	O
</s>
<s>
Doom	B-Application
is	I-Application
one	O
of	O
the	O
most	O
significant	O
games	O
in	O
video	B-Device
game	I-Device
history	I-Device
,	O
frequently	O
cited	O
as	O
one	O
of	O
the	O
greatest	O
games	O
ever	O
made	O
.	O
</s>
<s>
It	O
sold	O
an	O
estimated	O
3.5	O
million	O
copies	O
by	O
1999	O
;	O
between	O
10	O
and	O
20	O
million	O
people	O
are	O
estimated	O
to	O
have	O
played	O
it	O
within	O
two	O
years	O
of	O
launch	O
,	O
and	O
in	O
late	O
1995	O
,	O
it	O
was	O
estimated	O
to	O
be	O
installed	O
on	O
more	O
computers	O
worldwide	O
than	O
Microsoft	O
's	O
then-new	O
operating	O
system	O
,	O
Windows	B-Application
95	I-Application
.	O
</s>
<s>
Along	O
with	O
Wolfenstein	B-Application
3D	I-Application
,	O
Doom	B-Application
helped	O
define	O
the	O
FPS	O
genre	O
and	O
inspired	O
numerous	O
similar	O
games	O
,	O
often	O
called	O
Doom	B-Application
clones	B-General_Concept
.	O
</s>
<s>
Doom	B-Application
has	O
been	O
ported	O
to	O
numerous	O
platforms	O
.	O
</s>
<s>
The	O
Doom	B-Application
franchise	O
continued	O
with	O
Doom	B-Application
II	I-Application
:	I-Application
Hell	I-Application
on	I-Application
Earth	I-Application
(	O
1994	O
)	O
and	O
expansion	O
packs	O
including	O
Master	B-Application
Levels	I-Application
for	I-Application
Doom	I-Application
II	I-Application
(	O
1995	O
)	O
.	O
</s>
<s>
The	O
source	O
code	O
was	O
released	O
in	O
1997	O
under	O
a	O
proprietary	O
license	O
,	O
and	O
then	O
later	O
in	O
1999	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
v2.0	I-License
or	I-License
later	I-License
.	O
</s>
<s>
Doom	B-Application
3	I-Application
,	O
a	O
horror	O
game	O
built	O
with	O
the	O
id	B-Application
Tech	I-Application
4	I-Application
engine	O
,	O
was	O
released	O
in	O
2004	O
,	O
followed	O
by	O
a	O
2005	O
Doom	B-Application
film	O
.	O
</s>
<s>
id	O
returned	O
to	O
the	O
fast-paced	O
action	O
of	O
the	O
classic	O
games	O
with	O
the	O
2016	O
game	O
Doom	B-Application
and	O
the	O
2020	O
sequel	O
Doom	B-Application
Eternal	I-Application
.	O
</s>
<s>
Doom	B-Application
is	I-Application
a	O
first-person	O
shooter	O
presented	O
with	O
early	O
3D	O
graphics	O
.	O
</s>
<s>
The	O
player	O
controls	O
an	O
unnamed	O
space	B-Application
marine	I-Application
—	O
later	O
termed	O
"	O
Doomguy	O
"	O
—	O
through	O
a	O
series	O
of	O
levels	O
set	O
in	O
military	O
bases	O
on	O
the	O
moons	O
of	O
Mars	B-Application
and	O
in	O
hell	O
.	O
</s>
<s>
While	O
traversing	O
the	O
levels	O
,	O
the	O
player	O
must	O
fight	O
a	O
variety	O
of	O
enemies	O
,	O
including	O
demons	B-Operating_System
and	O
possessed	O
undead	O
humans	O
,	O
while	O
managing	O
supplies	O
of	O
ammunition	O
,	O
health	O
,	O
and	O
armor	O
.	O
</s>
<s>
They	O
will	O
reactively	B-Application
fight	I-Application
each	I-Application
other	I-Application
if	O
one	O
monster	O
inadvertently	O
harms	O
another	O
,	O
though	O
most	O
monsters	O
are	O
immune	O
to	O
attacks	O
from	O
their	O
own	O
kind	O
.	O
</s>
<s>
The	O
player	O
can	O
find	O
weapons	O
and	O
ammunition	O
throughout	O
the	O
levels	O
or	O
can	O
collect	O
them	O
from	O
dead	O
enemies	O
,	O
including	O
a	O
pistol	O
,	O
a	O
chainsaw	B-Language
,	O
a	O
plasma	O
rifle	O
,	O
and	O
the	O
BFG	O
9000	O
.	O
</s>
<s>
Doom	B-Application
is	I-Application
divided	O
into	O
three	O
episodes	O
:	O
"	O
Knee-Deep	B-Application
in	I-Application
the	I-Application
Dead	I-Application
"	O
,	O
"	O
The	B-Application
Shores	I-Application
of	I-Application
Hell	I-Application
"	O
,	O
and	O
"	O
Inferno	O
"	O
.	O
</s>
<s>
A	O
fourth	O
episode	O
,	O
"	O
Thy	B-Application
Flesh	I-Application
Consumed	I-Application
"	O
,	O
was	O
added	O
in	O
an	O
expanded	O
version	O
of	O
the	O
game	O
,	O
The	O
Ultimate	B-Application
Doom	I-Application
,	O
released	O
on	O
April	O
30	O
,	O
1995	O
,	O
two	O
years	O
after	O
Doom	B-Application
and	O
one	O
year	O
after	O
Doom	B-Application
II	I-Application
.	O
</s>
<s>
In	O
the	O
future	O
,	O
an	O
unnamed	O
marine	O
(	O
known	O
as	O
the	O
"	O
Doom	B-Application
marine	O
"	O
or	O
"	O
Doom	B-Application
guy	O
"	O
)	O
is	O
posted	O
to	O
a	O
dead-end	O
assignment	O
on	O
Mars	B-Application
after	O
assaulting	O
a	O
superior	O
officer	O
who	O
ordered	O
his	O
unit	O
to	O
fire	O
on	O
civilians	O
.	O
</s>
<s>
The	O
Union	B-Application
Aerospace	I-Application
Corporation	I-Application
,	O
which	O
operates	O
radioactive	O
waste	O
facilities	O
there	O
,	O
allows	O
the	O
military	O
to	O
conduct	O
secret	O
teleportation	B-General_Concept
experiments	O
that	O
go	O
terribly	O
wrong	O
.	O
</s>
<s>
In	O
"	O
Knee-Deep	B-Application
in	I-Application
the	I-Application
Dead	I-Application
"	O
,	O
the	O
marine	O
fights	O
demons	B-Operating_System
and	O
possessed	O
humans	O
in	O
the	O
military	O
and	O
waste	O
processing	O
facilities	O
on	O
Phobos	O
.	O
</s>
<s>
In	O
"	O
The	B-Application
Shores	I-Application
of	I-Application
Hell	I-Application
"	O
,	O
he	O
fights	O
on	O
through	O
Deimos	O
research	O
facilities	O
that	O
are	O
corrupted	O
with	O
satanic	O
architecture	O
and	O
kills	O
a	O
gigantic	O
cyberdemon	O
.	O
</s>
<s>
In	O
"	O
Inferno	O
"	O
,	O
the	O
marine	O
takes	O
on	O
hell	O
itself	O
and	O
destroys	O
a	O
cybernetic	O
spider-demon	O
that	O
masterminded	O
the	O
invasion	O
of	O
the	O
moons	O
.	O
</s>
<s>
"	O
Thy	B-Application
Flesh	I-Application
Consumed	I-Application
"	O
follows	O
the	O
marine	O
's	O
initial	O
assault	O
on	O
the	O
Earth	O
invasion	O
force	O
,	O
setting	O
the	O
stage	O
for	O
Doom	B-Application
II	I-Application
:	I-Application
Hell	I-Application
on	I-Application
Earth	I-Application
.	O
</s>
<s>
In	O
May	O
1992	O
,	O
id	O
Software	O
released	O
Wolfenstein	B-Application
3D	I-Application
,	O
later	O
called	O
the	O
"	O
grandfather	O
of	O
3D	O
shooters	O
"	O
,	O
specifically	O
first-person	O
shooters	O
,	O
because	O
it	O
established	O
the	O
fast-paced	O
action	O
and	O
technical	O
prowess	O
commonly	O
expected	O
in	O
the	O
genre	O
and	O
greatly	O
increased	O
the	O
genre	O
's	O
popularity	O
.	O
</s>
<s>
Immediately	O
following	O
its	O
release	O
most	O
of	O
the	O
id	O
Software	O
team	O
began	O
work	O
on	O
a	O
set	O
of	O
episodes	O
for	O
the	O
game	O
,	O
titled	O
Spear	B-Application
of	I-Application
Destiny	I-Application
,	O
while	O
id	O
co-founder	O
and	O
lead	O
programmer	O
John	O
Carmack	O
instead	O
focused	O
on	O
technology	O
research	O
for	O
the	O
company	O
's	O
next	O
game	O
.	O
</s>
<s>
Following	O
the	O
release	O
of	O
Spear	B-Application
of	I-Application
Destiny	I-Application
in	O
September	O
1992	O
,	O
the	O
team	O
began	O
to	O
plan	O
their	O
next	O
game	O
.	O
</s>
<s>
They	O
initially	O
considered	O
making	O
another	O
game	O
in	O
the	O
Commander	B-Application
Keen	I-Application
series	O
,	O
as	O
proposed	O
by	O
co-founder	O
and	O
lead	O
designer	O
Tom	O
Hall	O
,	O
but	O
decided	O
that	O
the	O
platforming	O
gameplay	O
of	O
the	O
series	O
was	O
a	O
poor	O
fit	O
for	O
Carmack	O
's	O
fast-paced	O
3D	O
engines	O
.	O
</s>
<s>
John	O
Carmack	O
then	O
came	O
up	O
with	O
his	O
own	O
concept	O
:	O
a	O
game	O
about	O
using	O
technology	O
to	O
fight	O
demons	B-Operating_System
,	O
inspired	O
by	O
the	O
Dungeons	O
&	O
Dragons	O
campaigns	O
the	O
team	O
played	O
,	O
combining	O
the	O
styles	O
of	O
Evil	O
Dead	O
II	O
and	O
Aliens	O
.	O
</s>
<s>
The	O
concept	O
originally	O
had	O
a	O
working	O
title	O
of	O
Green	O
and	O
Pissed	O
,	O
but	O
Carmack	O
soon	O
renamed	O
it	O
Doom	B-Application
after	O
a	O
line	O
in	O
the	O
1986	O
film	O
The	O
Color	O
of	O
Money	O
:	O
What	O
you	O
got	O
in	O
there	O
?	O
'	O
</s>
<s>
Doom	B-Application
.	O
</s>
<s>
The	O
team	O
agreed	O
to	O
pursue	O
the	O
Doom	B-Application
concept	O
,	O
and	O
development	O
began	O
in	O
November	O
1992	O
.	O
</s>
<s>
They	O
also	O
decided	O
to	O
cut	O
ties	O
with	O
Apogee	O
Software	O
,	O
their	O
previous	O
publisher	O
,	O
and	O
self-publish	O
Doom	B-Application
.	O
</s>
<s>
At	O
the	O
end	O
of	O
November	O
,	O
Hall	O
delivered	O
a	O
design	O
document	O
,	O
which	O
he	O
named	O
the	O
Doom	B-Application
Bible	O
,	O
that	O
described	O
the	O
plot	O
,	O
backstory	O
,	O
and	O
design	O
goals	O
for	O
the	O
project	O
.	O
</s>
<s>
Over	O
a	O
series	O
of	O
levels	O
,	O
the	O
player	O
discovers	O
that	O
the	O
aliens	O
are	O
demons	B-Operating_System
while	O
hell	O
steadily	O
infects	O
the	O
level	O
design	O
over	O
the	O
course	O
of	O
the	O
game	O
.	O
</s>
<s>
Hall	O
spent	O
the	O
next	O
few	O
weeks	O
reworking	O
the	O
Doom	B-Application
Bible	O
to	O
work	O
with	O
Carmack	O
's	O
technological	O
ideas	O
.	O
</s>
<s>
At	O
the	O
start	O
of	O
1993	O
,	O
id	O
put	O
out	O
a	O
press	O
release	O
,	O
touting	O
Hall	O
's	O
story	O
about	O
fighting	O
off	O
demons	B-Operating_System
while	O
"	O
knee-deep	B-Application
in	I-Application
the	I-Application
dead	I-Application
"	O
.	O
</s>
<s>
Early	O
versions	O
of	O
the	O
game	O
were	O
built	O
to	O
match	O
the	O
Doom	B-Application
Bible	O
;	O
a	O
"	O
pre-alpha	O
"	O
version	O
of	O
the	O
first	O
level	O
includes	O
Hall	O
's	O
introductory	O
base	O
scene	O
.	O
</s>
<s>
Initial	O
versions	O
of	O
the	O
game	O
also	O
retain	O
"	O
arcade	O
"	O
elements	O
present	O
in	O
Wolfenstein	B-Application
3D	I-Application
,	O
like	O
score	O
points	O
and	O
score	O
items	O
,	O
but	O
those	O
were	O
removed	O
early	O
in	O
development	O
as	O
they	O
were	O
not	O
in	O
keeping	O
with	O
the	O
tone	O
of	O
the	O
game	O
.	O
</s>
<s>
Soon	O
,	O
however	O
,	O
the	O
Doom	B-Application
Bible	O
as	O
a	O
whole	O
was	O
rejected	O
.	O
</s>
<s>
Petersen	O
and	O
Romero	O
designed	O
the	O
rest	O
of	O
Doom	B-Application
levels	O
,	O
with	O
different	O
aims	O
:	O
the	O
team	O
believed	O
that	O
Petersen	O
's	O
designs	O
were	O
more	O
technically	O
interesting	O
and	O
varied	O
,	O
while	O
Romero	O
's	O
were	O
more	O
aesthetically	O
interesting	O
.	O
</s>
<s>
According	O
to	O
Romero	O
,	O
the	O
game	O
's	O
deathmatch	O
mode	O
was	O
inspired	O
by	O
fighting	O
games	O
such	O
as	O
Street	B-Application
Fighter	I-Application
II	I-Application
,	O
Fatal	B-Application
Fury	I-Application
,	O
and	O
Art	B-Application
of	I-Application
Fighting	I-Application
.	O
</s>
<s>
Doom	B-Application
was	O
programmed	O
largely	O
in	O
the	O
ANSI	O
C	O
programming	O
language	O
,	O
with	O
a	O
few	O
elements	O
in	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
Development	O
was	O
done	O
on	O
NeXT	O
computers	O
running	O
the	O
NeXTSTEP	B-Application
operating	O
system	O
.	O
</s>
<s>
Carmack	O
designed	O
this	O
system	O
so	O
that	O
fans	O
could	O
easily	O
modify	O
the	O
game	O
;	O
he	O
had	O
been	O
impressed	O
by	O
the	O
modifications	O
made	O
by	O
fans	O
of	O
Wolfenstein	B-Application
3D	I-Application
,	O
and	O
wanted	O
to	O
support	O
that	O
with	O
an	O
easily	O
swappable	O
file	O
structure	O
along	O
with	O
releasing	O
the	O
map	O
editor	O
online	O
.	O
</s>
<s>
Unlike	O
Wolfenstein	O
,	O
which	O
had	O
flat	O
levels	O
with	O
walls	O
at	O
right	O
angles	O
,	O
the	O
Doom	B-Application
engine	I-Application
allows	O
for	O
walls	O
and	O
floors	O
at	O
any	O
angle	O
or	O
height	O
,	O
though	O
two	O
traversable	O
areas	O
cannot	O
be	O
on	O
top	O
of	O
each	O
other	O
.	O
</s>
<s>
The	O
lighting	O
system	O
was	O
based	O
on	O
adjusting	O
the	O
color	O
palette	O
of	O
surfaces	O
directly	O
:	O
rather	O
than	O
calculating	O
how	O
light	O
traveled	O
from	O
light	O
sources	O
to	O
surfaces	O
using	O
ray	B-Algorithm
tracing	I-Algorithm
,	O
the	O
game	O
calculates	O
the	O
"	O
light	O
level	O
"	O
of	O
a	O
small	O
area	O
based	O
on	O
the	O
predetermined	O
brightness	O
of	O
said	O
area	O
.	O
</s>
<s>
Adrian	O
Carmack	O
was	O
the	O
lead	O
artist	O
for	O
Doom	B-Application
,	O
with	O
Kevin	O
Cloud	O
as	O
an	O
additional	O
artist	O
.	O
</s>
<s>
Adrian	O
Carmack	O
made	O
clay	O
models	O
for	O
a	O
few	O
demons	B-Operating_System
,	O
and	O
had	O
Gregor	O
Punchatz	O
build	O
latex	O
and	O
metal	O
sculptures	O
of	O
the	O
others	O
.	O
</s>
<s>
As	O
with	O
Wolfenstein	B-Application
3D	I-Application
,	O
id	O
hired	O
composer	O
Bobby	O
Prince	O
to	O
create	O
the	O
music	O
and	O
sound	O
effects	O
.	O
</s>
<s>
With	O
plans	O
to	O
self-publish	O
,	O
the	O
team	O
had	O
to	O
set	O
up	O
the	O
systems	O
to	O
sell	O
Doom	B-Application
as	O
it	O
neared	O
completion	O
.	O
</s>
<s>
Jay	O
Wilbur	O
,	O
who	O
had	O
been	O
hired	O
as	O
CEO	O
and	O
sole	O
member	O
of	O
the	O
business	O
team	O
,	O
planned	O
the	O
marketing	O
and	O
distribution	O
of	O
Doom	B-Application
.	O
</s>
<s>
He	O
believed	O
that	O
the	O
mainstream	O
press	O
was	O
uninterested	O
in	O
the	O
game	O
,	O
and	O
as	O
id	O
would	O
make	O
the	O
most	O
money	O
off	O
copies	O
they	O
sold	O
directly	O
to	O
customers	O
—	O
up	O
to	O
85	O
percent	O
of	O
the	O
planned	O
price	O
—	O
he	O
decided	O
to	O
leverage	O
the	O
shareware	B-License
market	O
as	O
much	O
as	O
possible	O
,	O
buying	O
only	O
a	O
single	O
ad	O
in	O
any	O
gaming	O
magazine	O
.	O
</s>
<s>
Instead	O
,	O
he	O
reached	O
out	O
directly	O
to	O
software	O
retailers	O
,	O
offering	O
them	O
copies	O
of	O
the	O
first	O
Doom	B-Application
episode	O
for	O
free	O
,	O
allowing	O
them	O
to	O
charge	O
any	O
price	O
for	O
it	O
,	O
in	O
order	O
to	O
spur	O
customer	O
interest	O
in	O
buying	O
the	O
full	O
game	O
directly	O
from	O
id	O
.	O
</s>
<s>
Dooms	B-Application
original	O
release	O
date	O
was	O
the	O
third	O
quarter	O
of	O
1993	O
,	O
which	O
the	O
team	O
did	O
not	O
meet	O
.	O
</s>
<s>
So	O
many	O
users	O
were	O
connected	O
to	O
the	O
first	O
FTP	B-Protocol
server	O
that	O
they	O
planned	O
to	O
upload	O
the	O
game	O
to	O
,	O
at	O
the	O
University	O
of	O
Wisconsin	O
–	O
Madison	O
,	O
that	O
even	O
after	O
the	O
network	O
administrator	O
increased	O
the	O
number	O
of	O
connections	O
while	O
on	O
the	O
phone	O
with	O
Wilbur	O
,	O
id	O
was	O
unable	O
to	O
connect	O
,	O
leaving	O
network	O
admin	O
no	O
choice	O
but	O
to	O
kick	O
all	O
other	O
users	O
off	O
to	O
allow	O
id	O
to	O
successfully	O
upload	O
the	O
game	O
.	O
</s>
<s>
Within	O
hours	O
of	O
Dooms	B-Application
release	O
,	O
university	O
networks	O
were	O
banning	O
Doom	B-Application
multiplayer	O
games	O
,	O
as	O
a	O
rush	O
of	O
players	O
overwhelmed	O
their	O
systems	O
.	O
</s>
<s>
After	O
being	O
alerted	O
by	O
network	O
administrators	O
the	O
morning	O
after	O
release	O
that	O
the	O
game	O
's	O
deathmatch	O
network	O
connection	O
setup	O
was	O
crippling	O
some	O
computer	B-Architecture
networks	I-Architecture
,	O
John	O
Carmack	O
quickly	O
released	O
a	O
patch	O
to	O
change	O
it	O
,	O
though	O
many	O
administrators	O
had	O
to	O
implement	O
Doom-specific	O
rules	O
to	O
keep	O
their	O
networks	O
from	O
crashing	O
due	O
to	O
the	O
overwhelming	O
traffic	O
.	O
</s>
<s>
In	O
1995	O
,	O
an	O
expanded	O
version	O
of	O
Doom	B-Application
developed	O
for	O
the	O
retail	O
market	O
,	O
The	O
Ultimate	B-Application
Doom	I-Application
,	O
was	O
released	O
by	O
GT	O
Interactive	O
,	O
and	O
contained	O
a	O
fourth	O
episode	O
.	O
</s>
<s>
By	O
late	O
1995	O
,	O
Doom	B-Application
was	O
estimated	O
to	O
be	O
installed	O
on	O
more	O
computers	O
worldwide	O
than	O
Microsoft	O
's	O
new	O
operating	O
system	O
,	O
Windows	B-Application
95	I-Application
.	O
</s>
<s>
According	O
to	O
Windows	B-Application
producer	O
Gabe	O
Newell	O
,	O
who	O
later	O
founded	O
the	O
game	O
company	O
Valve	O
,	O
"[id]	O
...	O
did	O
n't	O
even	O
distribute	O
through	O
retail	O
,	O
it	O
distributed	O
through	O
bulletin	B-Application
boards	I-Application
and	O
other	O
pre-internet	O
mechanisms	O
.	O
</s>
<s>
Doom	B-Application
has	O
been	O
ported	O
to	O
numerous	O
different	O
platforms	O
,	O
though	O
none	O
were	O
by	O
id	O
Software	O
.	O
</s>
<s>
The	O
first	O
port	O
of	O
Doom	B-Application
was	O
an	O
unofficial	O
port	O
to	O
Linux	B-Application
,	O
released	O
by	O
id	O
programmer	O
Dave	O
Taylor	O
in	O
1994	O
;	O
it	O
was	O
hosted	O
by	O
id	O
but	O
not	O
supported	O
or	O
made	O
official	O
.	O
</s>
<s>
Microsoft	O
attempted	O
to	O
hire	O
id	O
to	O
port	O
Doom	B-Application
to	O
Windows	B-Application
in	O
1995	O
to	O
promote	O
Windows	B-Application
as	O
a	O
gaming	O
platform	O
,	O
and	O
Microsoft	O
CEO	O
Bill	O
Gates	O
briefly	O
considered	O
buying	O
the	O
company	O
.	O
</s>
<s>
One	O
promotional	O
video	O
for	O
Windows	B-Application
95	I-Application
had	O
Gates	O
digitally	O
superimposed	O
into	O
the	O
game	O
.	O
</s>
<s>
Other	O
official	O
ports	O
of	O
the	O
game	O
were	O
released	O
for	O
Sega	B-Device
32X	I-Device
,	O
Atari	B-Device
Jaguar	I-Device
,	O
and	O
Mac	B-Application
OS	I-Application
in	O
1994	O
,	O
SNES	B-Application
and	O
PlayStation	B-Device
in	O
1995	O
,	O
3DO	B-Device
in	O
1996	O
,	O
Sega	B-Device
Saturn	I-Device
in	O
1997	O
,	O
Acorn	B-Device
Risc	I-Device
PC	I-Device
in	O
1998	O
,	O
Game	B-Device
Boy	I-Device
Advance	I-Device
in	O
2001	O
,	O
Xbox	B-Operating_System
360	I-Operating_System
in	O
2006	O
,	O
iOS	B-Application
in	O
2009	O
,	O
and	O
Nintendo	B-Application
Switch	I-Application
in	O
2019	O
.	O
</s>
<s>
Doom	B-Application
has	O
also	O
been	O
ported	O
unofficially	O
to	O
numerous	O
platforms	O
;	O
so	O
many	O
ports	O
exist	O
,	O
including	O
for	O
esoteric	O
devices	O
such	O
as	O
smart	O
thermostats	O
and	O
oscilloscopes	O
,	O
that	O
variations	O
on	O
"	O
It	O
runs	O
Doom	B-Application
"	O
or	O
"	O
Can	O
it	O
run	O
Doom	B-Application
?	O
"	O
</s>
<s>
Although	O
Petersen	O
said	O
Doom	B-Application
was	O
"	O
nothing	O
more	O
than	O
the	O
computer	O
equivalent	O
of	O
Whack-A-Mole	O
"	O
,	O
Doom	B-Application
received	O
critical	O
acclaim	O
and	O
was	O
widely	O
praised	O
in	O
the	O
gaming	O
press	O
,	O
broadly	O
considered	O
to	O
be	O
one	O
of	O
the	O
most	O
important	O
and	O
influential	O
titles	O
in	O
gaming	O
history	O
.	O
</s>
<s>
Dragon	O
gave	O
it	O
five	O
stars	O
,	O
praising	O
the	O
improvements	O
over	O
Wolfenstein	B-Application
3D	I-Application
,	O
the	O
"	O
fast-moving	O
arcade	O
shoot	O
'	O
em	O
up	O
"	O
gameplay	O
,	O
and	O
network	O
play	O
.	O
</s>
<s>
A	O
common	O
criticism	O
of	O
Doom	B-Application
was	O
that	O
it	O
was	O
not	O
a	O
true	O
3D	O
game	O
,	O
since	O
the	O
game	O
engine	O
did	O
not	O
allow	O
corridors	O
and	O
rooms	O
to	O
be	O
stacked	O
on	O
top	O
of	O
one	O
another	O
(	O
room-over-room	O
)	O
,	O
and	O
instead	O
relied	O
on	O
graphical	O
trickery	O
to	O
make	O
it	O
appear	O
that	O
the	O
player	O
character	O
and	O
enemies	O
were	O
moving	O
along	O
differing	O
elevations	O
.	O
</s>
<s>
Computer	O
Gaming	O
World	O
stated	O
in	O
February	O
1994	O
that	O
Wolfenstein	B-Application
3D	I-Application
fans	O
should	O
"	O
look	O
forward	O
to	O
a	O
delight	O
of	O
insomnia	O
"	O
,	O
and	O
"	O
Since	O
networking	O
is	O
supported	O
,	O
bring	O
along	O
a	O
friend	O
to	O
share	O
in	O
the	O
visceral	O
delights	O
"	O
.	O
</s>
<s>
A	O
longer	O
review	O
in	O
March	O
1994	O
said	O
that	O
Doom	B-Application
"	O
was	O
worth	O
the	O
wait	O
...	O
a	O
wonderfully	O
involved	O
and	O
engaging	O
game	O
"	O
,	O
and	O
its	O
technology	O
"	O
a	O
new	O
benchmark	O
"	O
for	O
the	O
gaming	O
industry	O
.	O
</s>
<s>
While	O
criticizing	O
the	O
"	O
ho-hum	O
endgame	O
"	O
with	O
a	O
too-easy	O
end	O
boss	O
,	O
he	O
concluded	O
that	O
Doom	B-Application
"	O
is	O
a	O
virtuoso	O
performance	O
"	O
.	O
</s>
<s>
Edge	O
praised	O
the	O
graphics	O
and	O
levels	O
but	O
criticized	O
the	O
"	O
simple	O
3D	O
perspective	O
maze	B-Application
adventure/shoot	O
'	O
em	O
up	O
"	O
gameplay	O
.	O
</s>
<s>
A	O
2016	O
piece	O
in	O
the	O
International	O
Business	O
Times	O
defended	O
the	O
sentiment	O
,	O
saying	O
it	O
anticipated	O
the	O
dialogue	O
systems	O
of	O
games	O
such	O
as	O
The	B-Application
Elder	I-Application
Scrolls	I-Application
V	I-Application
:	I-Application
Skyrim	I-Application
,	O
Mass	B-Application
Effect	I-Application
and	O
Undertale	B-Application
.	O
</s>
<s>
In	O
1994	O
,	O
PC	O
Gamer	O
UK	O
named	O
Doom	B-Application
the	O
third-best	O
computer	O
game	O
of	O
all	O
time	O
.	O
</s>
<s>
The	O
editors	O
wrote	O
:	O
"	O
Although	O
it	O
's	O
only	O
been	O
around	O
for	O
a	O
couple	O
of	O
months	O
,	O
Doom	B-Application
has	O
already	O
done	O
more	O
to	O
establish	O
the	O
PC	O
's	O
arcade	O
clout	O
than	O
any	O
other	O
title	O
in	O
gaming	O
history.	O
"	O
</s>
<s>
In	O
1994	O
Computer	O
Gaming	O
World	O
named	O
Doom	B-Application
Game	I-Application
of	O
the	O
Year	O
.	O
</s>
<s>
The	O
various	O
Doom	B-Application
console	O
ports	O
have	O
received	O
generally	O
favorable	O
reviews	O
.	O
</s>
<s>
Running	O
on	O
a	O
486	B-General_Concept
machine	O
(	O
essential	O
for	O
maximum	O
effect	O
)	O
,	O
Doom	B-Application
took	O
PC	O
graphics	O
to	O
a	O
totally	O
new	O
level	O
of	O
speed	O
,	O
detail	O
,	O
and	O
realism	O
,	O
and	O
provided	O
a	O
genuinely	O
scary	O
degree	O
of	O
immersion	O
in	O
the	O
gameworld.	O
"	O
</s>
<s>
In	O
1996	O
,	O
GamesMaster	O
rated	O
the	O
SNES	B-Application
version	O
7th	O
on	O
their	O
"	O
The	O
Gamesmaster	O
SNES	B-Application
Top	O
10.	O
"	O
</s>
<s>
In	O
1998	O
,	O
PC	O
Gamer	O
declared	O
it	O
the	O
34th-best	O
computer	O
game	O
ever	O
released	O
,	O
and	O
the	O
editors	O
called	O
it	O
"	O
Probably	O
the	O
most	O
imitated	O
game	O
of	O
all	O
time	O
,	O
Doom	B-Application
continued	O
what	O
Wolfenstein	B-Application
3D	I-Application
began	O
and	O
elevated	O
the	O
fledgling	O
3D-shooter	O
genre	O
to	O
blockbuster	O
status	O
"	O
.	O
</s>
<s>
In	O
2001	O
,	O
Doom	B-Application
was	O
voted	O
the	O
number	O
one	O
game	O
of	O
all	O
time	O
in	O
a	O
poll	O
among	O
over	O
100	O
game	O
developers	O
and	O
journalists	O
conducted	O
by	O
GameSpy	O
.	O
</s>
<s>
PC	O
Gamer	O
proclaimed	O
Doom	B-Application
the	O
most	O
influential	O
game	O
of	O
all	O
time	O
in	O
its	O
ten-year	O
anniversary	O
issue	O
in	O
April	O
2004	O
.	O
</s>
<s>
In	O
2004	O
,	O
readers	O
of	O
Retro	O
Gamer	O
voted	O
Doom	B-Application
as	O
the	O
ninth	O
top	O
retro	O
game	O
,	O
with	O
the	O
editors	O
commenting	O
:	O
"	O
Only	O
a	O
handful	O
of	O
games	O
can	O
claim	O
that	O
they	O
've	O
changed	O
the	O
gaming	O
world	O
,	O
and	O
Doom	B-Application
is	I-Application
perhaps	O
the	O
most	O
qualified	O
of	O
them	O
all.	O
"	O
</s>
<s>
On	O
March	O
12	O
,	O
2007	O
,	O
The	O
New	O
York	O
Times	O
reported	O
that	O
Doom	B-Application
was	O
named	O
to	O
a	O
list	O
of	O
the	O
ten	O
most	O
important	O
video	O
games	O
of	O
all	O
time	O
,	O
the	O
so-called	O
game	O
canon	O
.	O
</s>
<s>
In	O
2009	O
,	O
GameTrailers	O
ranked	O
Doom	B-Application
as	O
the	O
number	O
one	O
"	O
breakthrough	O
PC	O
game	O
"	O
.	O
</s>
<s>
That	O
year	O
Game	O
Informer	O
put	O
Doom	B-Application
sixth	O
on	O
the	O
magazine	O
's	O
list	O
of	O
the	O
top	O
200	O
games	O
of	O
all	O
time	O
,	O
stating	O
that	O
it	O
gave	O
"	O
the	O
genre	O
the	O
kick	O
start	O
it	O
needed	O
to	O
rule	O
the	O
gaming	O
landscape	O
two	O
decades	O
later	O
"	O
.	O
</s>
<s>
IGN	O
included	O
Doom	B-Application
at	O
2nd	O
place	O
in	O
the	O
Top	O
100	O
Video	O
Game	O
Shooters	O
of	O
all	O
Time	O
,	O
just	O
behind	O
Half-Life	B-Application
,	O
citing	O
the	O
game	O
's	O
"	O
feel	O
of	O
running	O
and	O
gunning	O
"	O
,	O
memorable	O
weapons	O
and	O
enemies	O
,	O
pure	O
and	O
simple	O
fun	O
,	O
and	O
its	O
spreading	O
on	O
nearly	O
every	O
gaming	O
platform	O
in	O
existence	O
.	O
</s>
<s>
In	O
2012	O
,	O
Time	O
named	O
it	O
one	O
of	O
the	O
100	O
greatest	O
video	O
games	O
of	O
all	O
time	O
as	O
"	O
it	O
established	O
the	O
look	O
and	O
feel	O
of	O
later	O
shooters	O
as	O
surely	O
as	O
Xerox	O
PARC	O
established	O
the	O
rules	O
of	O
the	O
virtual	B-Application
desktop	I-Application
"	O
,	O
adding	O
that	O
"	O
its	O
impact	O
also	O
owes	O
a	O
lot	O
to	O
the	O
gonzo	O
horror	O
sensibility	O
of	O
its	O
designers	O
,	O
including	O
John	O
Romero	O
,	O
who	O
showed	O
a	O
bracing	O
lack	O
of	O
restraint	O
in	O
their	O
deployment	O
of	O
gore	O
and	O
Satanic	O
iconography	O
"	O
.	O
</s>
<s>
Including	O
Doom	B-Application
on	O
the	O
list	O
of	O
the	O
greatest	O
games	O
of	O
all	O
time	O
,	O
GameSpot	O
wrote	O
that	O
"	O
despite	O
its	O
numerous	O
appearances	O
in	O
other	O
formats	O
and	O
on	O
other	O
media	O
,	O
longtime	O
fans	O
will	O
forever	O
remember	O
the	O
original	O
1993	O
release	O
of	O
Doom	B-Application
as	O
the	O
beginning	O
of	O
a	O
true	O
revolution	O
in	O
action	O
gaming	O
"	O
.	O
</s>
<s>
In	O
2015	O
,	O
The	O
Strong	O
National	O
Museum	O
of	O
Play	O
inducted	O
Doom	B-Application
to	O
its	O
World	O
Video	O
Game	O
Hall	O
of	O
Fame	O
.	O
</s>
<s>
In	O
2018	O
,	O
Complex	O
listed	O
the	O
game	O
#47	O
in	O
their	O
"	O
The	O
Best	O
Super	B-Application
Nintendo	I-Application
Games	O
of	O
All	O
Time.	O
"	O
</s>
<s>
In	O
2021	O
,	O
Kotaku	O
listed	O
Doom	B-Application
as	O
the	O
third	O
best	O
game	O
in	O
the	O
series	O
,	O
behind	O
Doom	B-Application
II	I-Application
and	O
Doom	B-Application
(	O
2016	O
)	O
.	O
</s>
<s>
They	O
said	O
that	O
the	O
gameplay	O
"	O
still	O
holds	O
up	O
"	O
,	O
but	O
argued	O
it	O
was	O
inferior	O
to	O
Doom	B-Application
II	I-Application
due	O
to	O
the	O
latter	O
's	O
improved	O
enemy	O
variety	O
.	O
</s>
<s>
With	O
the	O
release	O
of	O
Doom	B-Application
,	O
millions	O
of	O
users	O
installed	O
the	O
Shareware	B-License
version	O
on	O
their	O
computer	O
and	O
id	O
Software	O
quickly	O
began	O
making	O
$	O
100,000	O
daily	O
(	O
for	O
$9	O
per	O
copy	O
)	O
.	O
</s>
<s>
According	O
to	O
PC	O
Data	O
,	O
which	O
tracked	O
sales	O
in	O
the	O
United	O
States	O
,	O
by	O
April	O
1998	O
Dooms	B-Application
shareware	B-License
edition	O
had	O
yielded	O
1.36	O
million	O
units	O
sold	O
and	O
$8.74	O
million	O
in	O
revenue	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
The	O
Ultimate	B-Application
Doom	I-Application
SKU	O
reached	O
sales	O
of	O
787,397	O
units	O
by	O
September	O
1999	O
.	O
</s>
<s>
In	O
addition	O
to	O
its	O
sales	O
,	O
the	O
game	O
's	O
status	O
as	O
shareware	B-License
dramatically	O
increased	O
its	O
market	O
penetration	O
.	O
</s>
<s>
PC	O
Zones	O
David	O
McCandless	O
wrote	O
that	O
the	O
game	O
was	O
played	O
by	O
"	O
an	O
estimated	O
six	O
million	O
people	O
across	O
the	O
globe	O
"	O
,	O
and	O
other	O
sources	O
estimate	O
that	O
10	O
–	O
20	O
million	O
people	O
played	O
Doom	B-Application
within	O
24	O
months	O
of	O
its	O
launch	O
.	O
</s>
<s>
Doom	B-Application
became	O
a	O
problem	O
at	O
workplaces	O
,	O
both	O
occupying	O
the	O
time	O
of	O
employees	O
and	O
clogging	O
computer	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
Intel	O
,	O
Lotus	O
Development	O
,	O
and	O
Carnegie	O
Mellon	O
University	O
were	O
among	O
many	O
organizations	O
reported	O
to	O
form	O
policies	O
specifically	O
disallowing	O
Doom-playing	O
during	O
work	O
hours	O
.	O
</s>
<s>
At	O
the	O
Microsoft	O
campus	O
,	O
Doom	B-Application
was	O
by	O
one	O
account	O
equal	O
to	O
a	O
"	O
religious	O
phenomenon	O
"	O
.	O
</s>
<s>
Doom	B-Application
was	O
#1	O
on	O
Computer	O
Gaming	O
Worlds	O
"	O
Playing	O
Lately	O
?	O
"	O
</s>
<s>
The	O
only	O
game	O
I	O
've	O
stayed	O
up	O
72+	O
straight	O
hours	O
to	O
play	O
"	O
,	O
and	O
another	O
reported	O
that	O
"	O
Linking	O
four	O
people	O
together	O
for	O
a	O
game	O
of	O
Doom	B-Application
is	I-Application
the	O
quickest	O
way	O
to	O
destroy	O
a	O
productive	O
,	O
boring	O
evening	O
of	O
work	O
"	O
.	O
</s>
<s>
Doom	B-Application
was	O
notorious	O
for	O
its	O
high	O
levels	O
of	O
graphic	O
violence	O
and	O
satanic	O
imagery	O
,	O
which	O
generated	O
controversy	O
from	O
a	O
broad	O
range	O
of	O
groups	O
.	O
</s>
<s>
Doom	B-Application
for	O
the	O
32X	B-Device
was	O
one	O
of	O
the	O
first	O
video	O
games	O
to	O
be	O
given	O
an	O
M	O
for	O
Mature	O
rating	O
from	O
the	O
Entertainment	O
Software	O
Rating	O
Board	O
due	O
to	O
its	O
violent	O
gore	O
and	O
nature	O
.	O
</s>
<s>
Doom	B-Application
prompted	O
fears	O
that	O
the	O
then-emerging	O
virtual	B-Application
reality	I-Application
technology	O
could	O
be	O
used	O
to	O
simulate	O
extremely	O
realistic	O
killing	O
.	O
</s>
<s>
While	O
planning	O
for	O
the	O
massacre	O
,	O
Harris	O
said	O
in	O
his	O
journal	O
that	O
the	O
killing	O
would	O
be	O
"	O
like	O
playing	O
Doom	B-Application
"	O
,	O
and	O
"	O
it	O
'll	O
be	O
like	O
the	O
LA	O
riots	O
,	O
the	O
Oklahoma	O
bombing	O
,	O
World	O
War	O
II	O
,	O
Vietnam	O
,	O
Duke	B-Application
Nukem	I-Application
and	O
Doom	B-Application
all	O
mixed	O
together	O
"	O
,	O
and	O
that	O
his	O
shotgun	O
was	O
"	O
straight	O
out	O
of	O
the	O
game	O
"	O
.	O
</s>
<s>
A	O
rumor	O
spread	O
afterwards	O
that	O
Harris	O
had	O
designed	O
a	O
custom	O
Doom	B-Application
level	O
,	O
known	O
as	O
a	O
"	O
Doom	B-Application
WAD	O
"	O
that	O
looked	O
like	O
the	O
high	O
school	O
,	O
populated	O
with	O
representations	O
of	O
Harris	O
's	O
classmates	O
and	O
teachers	O
,	O
and	O
that	O
he	O
practiced	O
for	O
the	O
shootings	O
by	O
playing	O
the	O
level	O
repeatedly	O
.	O
</s>
<s>
Although	O
Harris	O
did	O
design	O
several	O
custom	O
Doom	B-Application
levels	O
(	O
which	O
later	O
became	O
known	O
as	O
the	O
"	O
Harris	O
levels	O
"	O
)	O
,	O
none	O
have	O
been	O
found	O
to	O
be	O
based	O
on	O
Columbine	O
High	O
School	O
.	O
</s>
<s>
In	O
the	O
earliest	O
release	O
versions	O
,	O
the	O
level	O
E1M4	O
:	O
Command	O
Control	O
contains	O
a	O
swastika-shaped	O
structure	O
,	O
which	O
was	O
put	O
in	O
as	O
a	O
homage	O
to	O
Wolfenstein	B-Application
3D	I-Application
.	O
</s>
<s>
Doom	B-Application
has	O
appeared	O
in	O
several	O
forms	O
in	O
addition	O
to	O
video	O
games	O
,	O
including	O
a	O
Doom	B-Application
comic	O
book	O
,	O
four	O
novels	O
by	O
Dafydd	O
Ab	O
Hugh	O
and	O
Brad	O
Linaweaver	O
(	O
loosely	O
based	O
on	O
events	O
and	O
locations	O
in	O
the	O
games	O
)	O
,	O
a	O
Doom	B-Application
board	O
game	O
and	O
a	O
live-action	O
film	O
starring	O
Karl	O
Urban	O
and	O
The	O
Rock	O
released	O
in	O
2005	O
.	O
</s>
<s>
The	O
game	O
's	O
development	O
and	O
impact	O
on	O
popular	O
culture	O
is	O
the	O
subject	O
of	O
the	O
book	O
Masters	O
of	O
Doom	B-Application
:	O
How	O
Two	O
Guys	O
Created	O
an	O
Empire	O
and	O
Transformed	O
Pop	O
Culture	O
by	O
David	O
Kushner	O
.	O
</s>
<s>
The	O
Doom	B-Application
series	I-Application
remained	O
dormant	O
between	O
1997	O
and	O
2000	O
,	O
when	O
Doom	B-Application
3	I-Application
was	O
finally	O
announced	O
.	O
</s>
<s>
A	O
retelling	O
of	O
the	O
original	O
Doom	B-Application
using	O
entirely	O
new	O
graphics	O
technology	O
and	O
a	O
slower	O
paced	O
survival	O
horror	O
approach	O
,	O
Doom	B-Application
3	I-Application
was	O
hyped	O
to	O
provide	O
as	O
large	O
a	O
leap	O
in	O
realism	O
and	O
interactivity	O
as	O
the	O
original	O
game	O
and	O
helped	O
renew	O
interest	O
in	O
the	O
franchise	O
when	O
it	O
was	O
released	O
in	O
2004	O
,	O
under	O
the	O
id	B-Application
Tech	I-Application
4	I-Application
game	O
engine	O
.	O
</s>
<s>
The	O
series	O
again	O
remained	O
dormant	O
for	O
10	O
years	O
until	O
a	O
reboot	O
,	O
simply	O
titled	O
Doom	B-Application
and	O
running	O
on	O
the	O
new	O
id	B-Operating_System
Tech	I-Operating_System
6	I-Operating_System
,	O
was	O
announced	O
with	O
a	O
beta	O
access	O
to	O
players	O
that	O
had	O
pre-ordered	O
Wolfenstein	B-Application
:	I-Application
The	I-Application
New	I-Application
Order	I-Application
.	O
</s>
<s>
The	O
project	O
initially	O
started	O
as	O
Doom	B-Application
4	I-Application
in	O
May	O
2008	O
,	O
set	O
to	O
be	O
a	O
remake	B-General_Concept
of	O
Doom	B-Application
II	I-Application
:	I-Application
Hell	I-Application
on	I-Application
Earth	I-Application
and	O
ditching	O
the	O
survival	O
horror	O
aspect	O
of	O
Doom	B-Application
3	I-Application
.	O
</s>
<s>
Development	O
completely	O
restarted	O
as	O
id	O
's	O
Tim	O
Willits	O
remarked	O
that	O
Doom	B-Application
4	I-Application
was	O
"	O
lacking	O
the	O
personality	O
of	O
the	O
long-running	O
shooter	O
franchise	O
"	O
.	O
</s>
<s>
The	O
ability	O
for	O
user-generated	O
content	O
to	O
provide	O
custom	O
levels	O
and	O
other	O
game	O
modifications	O
using	O
WAD	O
files	O
became	O
a	O
popular	O
aspect	O
of	O
Doom	B-Application
.	O
</s>
<s>
Gaining	O
the	O
first	O
large	O
mod-making	O
community	O
,	O
Doom	B-Application
affected	O
the	O
culture	O
surrounding	O
first-person	O
shooters	O
,	O
and	O
also	O
the	O
industry	O
.	O
</s>
<s>
Several	O
future	O
professional	O
game	O
designers	O
started	O
their	O
careers	O
making	O
Doom	B-Application
WADs	O
as	O
a	O
hobby	O
,	O
such	O
as	O
Tim	O
Willits	O
,	O
who	O
later	O
became	O
the	O
lead	O
designer	O
at	O
id	O
Software	O
.	O
</s>
<s>
Several	O
popular	O
movies	O
,	O
television	O
series	O
,	O
other	O
video	O
games	O
and	O
other	O
brands	O
from	O
popular	O
culture	O
have	O
been	O
turned	O
into	O
Doom	B-Application
WADs	O
by	O
fans	O
,	O
including	O
Aliens	O
,	O
Star	B-Application
Wars	I-Application
,	O
The	B-Application
Simpsons	I-Application
,	O
South	B-Application
Park	I-Application
,	O
Sailor	B-Application
Moon	I-Application
,	O
Dragon	O
Ball	O
Z	O
,	O
Pokémon	B-Application
,	O
Beavis	O
and	O
Butt-head	O
,	O
Batman	B-General_Concept
,	O
and	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
.	O
</s>
<s>
Some	O
works	O
,	O
like	O
the	O
Theme	O
Doom	B-Application
Patch	O
,	O
combined	O
enemies	O
from	O
several	O
films	O
,	O
such	O
as	O
Aliens	O
,	O
Predator	O
,	O
and	O
The	B-General_Concept
Terminator	I-General_Concept
.	O
</s>
<s>
From	O
1994	O
to	O
1995	O
,	O
WADs	O
were	O
primarily	O
distributed	O
online	O
over	O
bulletin	B-Application
board	I-Application
systems	I-Application
or	O
sold	O
in	O
collections	O
on	O
compact	O
discs	O
in	O
computer	O
shops	O
,	O
sometimes	O
bundled	O
with	O
editing	O
guide	O
books	O
.	O
</s>
<s>
FTP	B-Protocol
servers	O
became	O
the	O
primary	O
method	O
in	O
later	O
years	O
.	O
</s>
<s>
A	O
few	O
WADs	O
have	O
been	O
released	O
commercially	O
,	O
including	O
the	O
Master	B-Application
Levels	I-Application
for	I-Application
Doom	I-Application
II	I-Application
,	O
which	O
was	O
released	O
in	O
1995	O
along	O
with	O
Maximum	O
Doom	B-Application
,	O
a	O
CD	O
containing	O
1,830	O
WADs	O
that	O
had	O
been	O
downloaded	O
from	O
the	O
Internet	O
.	O
</s>
<s>
The	O
idgames	O
FTP	B-Protocol
archive	O
contains	O
more	O
than	O
18,000	O
files	O
,	O
and	O
this	O
represents	O
only	O
a	O
fraction	O
of	O
the	O
complete	O
output	O
of	O
Doom	B-Application
fans	O
.	O
</s>
<s>
Third-party	O
programs	O
were	O
also	O
written	O
to	O
handle	O
the	O
loading	O
of	O
various	O
WADs	O
,	O
since	O
all	O
commands	O
must	O
be	O
entered	O
on	O
the	O
DOS	B-Device
command	B-Application
line	I-Application
to	O
run	O
.	O
</s>
<s>
In	O
1995	O
,	O
WizardWorks	O
released	O
the	O
D	O
!	O
Zone	O
pack	O
featuring	O
hundreds	O
of	O
levels	O
for	O
Doom	B-Application
and	O
Doom	B-Application
II	I-Application
.	O
</s>
<s>
In	O
2016	O
,	O
Romero	O
published	O
two	O
new	O
Doom	B-Application
levels	O
:	O
E1M4b	O
(	O
"	O
Phobos	O
Mission	O
Control	O
"	O
)	O
and	O
E1M8b	O
(	O
"	O
Tech	O
Gone	O
Bad	O
"	O
)	O
.	O
</s>
<s>
In	O
2018	O
,	O
for	O
the	O
25th	O
anniversary	O
of	O
Doom	B-Application
,	O
Romero	O
announced	O
Sigil	B-Application
,	O
an	O
unofficial	O
Episode	O
Five	O
consisting	O
of	O
9	O
missions	O
.	O
</s>
<s>
Doom	B-Application
was	O
influential	O
and	O
dozens	O
of	O
new	O
first-person	O
shooter	O
games	O
appeared	O
following	O
Dooms	B-Application
release	O
,	O
often	O
referred	O
to	O
as	O
"	O
Doom	B-Application
clones	B-General_Concept
"	O
.	O
</s>
<s>
Some	O
of	O
these	O
were	O
cheap	O
clones	B-General_Concept
,	O
hastily	O
assembled	O
and	O
quickly	O
forgotten	O
,	O
and	O
others	O
explored	O
new	O
grounds	O
of	O
the	O
genre	O
with	O
high	O
acclaim	O
.	O
</s>
<s>
Many	O
of	O
Dooms	B-Application
closely	O
imitated	O
features	O
include	O
the	O
selection	O
of	O
weapons	O
and	O
cheat	O
codes	O
.	O
</s>
<s>
Some	O
successors	O
include	O
Apogee	O
's	O
Rise	B-Application
of	I-Application
the	I-Application
Triad	I-Application
(	O
based	O
on	O
the	O
Wolfenstein	B-Application
3D	I-Application
engine	O
)	O
and	O
Looking	O
Glass	O
Studios	O
's	O
System	B-Application
Shock	I-Application
.	O
</s>
<s>
The	O
popularity	O
of	O
Star	O
Wars-themed	O
WADs	O
is	O
rumored	O
to	O
have	O
been	O
the	O
factor	O
that	O
prompted	O
LucasArts	O
to	O
create	O
their	O
first-person	O
shooter	O
Dark	B-Application
Forces	I-Application
.	O
</s>
<s>
The	O
Doom	B-Application
engine	I-Application
was	O
licensed	O
by	O
id	O
Software	O
to	O
several	O
other	O
companies	O
,	O
who	O
released	O
their	O
own	O
games	O
using	O
the	O
technology	O
,	O
including	O
Heretic	B-Application
,	O
Hexen	B-Application
:	I-Application
Beyond	I-Application
Heretic	I-Application
,	O
Strife	B-Application
:	I-Application
Quest	I-Application
for	I-Application
the	I-Application
Sigil	I-Application
,	O
and	O
Hacx	O
:	O
Twitch	O
'	O
n	O
Kill	O
.	O
</s>
<s>
A	O
Doom-based	O
game	O
called	O
Chex	B-Application
Quest	I-Application
was	O
released	O
in	O
1996	O
by	O
Ralston	O
Foods	O
as	O
a	O
promotion	O
to	O
increase	O
cereal	O
sales	O
,	O
and	O
the	O
United	O
States	O
Marine	O
Corps	O
produced	O
Marine	B-Application
Doom	I-Application
as	O
a	O
training	O
tool	O
,	O
later	O
released	O
to	O
the	O
public	O
.	O
</s>
<s>
Some	O
Doom	B-Application
clones	B-General_Concept
were	O
n't	O
just	O
content	O
with	O
just	O
using	O
the	O
original	O
engine	O
without	O
own	O
improvements	O
by	O
develophers	O
,	O
such	O
as	O
Team17	O
's	O
1995	O
game	O
Alien	B-Application
Breed	I-Application
3D	I-Application
,	O
which	O
presents	O
capable	O
of	O
maps	O
of	O
varying	O
depths	O
with	O
platforms	O
and	O
floors	O
above	O
others	O
,	O
something	O
the	O
Doom	B-Application
engine	I-Application
was	O
not	O
capable	O
of	O
.	O
</s>
<s>
When	O
3D	O
Realms	O
released	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
in	O
1996	O
,	O
a	O
tongue-in-cheek	O
science	O
fiction	O
shooter	O
based	O
on	O
Ken	O
Silverman	O
's	O
technologically	O
similar	O
Build	B-Application
engine	I-Application
,	O
id	O
Software	O
had	O
nearly	O
finished	O
developing	O
Quake	B-Application
,	O
its	O
next-generation	O
game	O
,	O
which	O
mirrored	O
Dooms	B-Application
success	O
for	O
much	O
of	O
the	O
remainder	O
of	O
the	O
1990s	O
and	O
reduced	O
interest	O
in	O
its	O
predecessor	O
(	O
Wolfenstein	B-Application
3D	I-Application
)	O
.	O
</s>
<s>
Doom	B-Application
was	O
not	O
the	O
first	O
first-person	O
shooter	O
with	O
a	O
deathmatch	O
mode	O
;	O
Maze	B-Application
War	I-Application
,	O
an	O
FPS	O
released	O
in	O
1974	O
,	O
was	O
running	O
multiplayer	O
deathmatch	O
over	O
ethernet	O
on	O
Xerox	O
computers	O
by	O
1977	O
.	O
</s>
<s>
The	O
widespread	O
distribution	O
of	O
PC	O
systems	O
and	O
the	O
violence	O
in	O
Doom	B-Application
made	O
deathmatching	O
particularly	O
attractive	O
.	O
</s>
<s>
Two-player	O
multiplayer	O
was	O
possible	O
over	O
a	O
phone	O
line	O
by	O
using	O
a	O
modem	B-Application
,	O
or	O
by	O
linking	O
two	O
PCs	O
with	O
a	O
null-modem	O
cable	O
.	O
</s>
<s>
Because	O
of	O
its	O
widespread	O
distribution	O
,	O
Doom	B-Application
hence	O
became	O
the	O
game	O
that	O
introduced	O
deathmatching	O
to	O
a	O
large	O
audience	O
and	O
was	O
also	O
the	O
first	O
game	O
to	O
use	O
the	O
term	O
"	O
deathmatch	O
"	O
.	O
</s>
<s>
Although	O
the	O
popularity	O
of	O
the	O
Doom	B-Application
games	I-Application
dropped	O
with	O
the	O
release	O
of	O
more	O
modern	O
first-person	O
shooters	O
,	O
the	O
game	O
still	O
retains	O
a	O
strong	O
fan	O
base	O
that	O
continues	O
to	O
this	O
day	O
by	O
playing	O
competitively	O
and	O
creating	O
WADs	O
,	O
and	O
Doom-related	O
news	O
is	O
still	O
tracked	O
at	O
multiple	O
websites	O
such	O
as	O
Doomworld	O
.	O
</s>
<s>
Interest	O
in	O
Doom	B-Application
was	O
renewed	O
in	O
1997	O
,	O
when	O
the	O
source	O
code	O
for	O
the	O
Doom	B-Application
engine	I-Application
was	O
released	O
(	O
it	O
was	O
also	O
placed	O
under	O
the	O
GNU	B-License
GPL-2.0-or-later	I-License
on	O
October	O
3	O
,	O
1999	O
)	O
.	O
</s>
<s>
Fans	O
then	O
began	O
porting	O
the	O
game	O
to	O
various	O
operating	O
systems	O
,	O
even	O
to	O
previously	O
unsupported	O
platforms	O
such	O
as	O
the	B-Operating_System
Dreamcast	I-Operating_System
.	O
</s>
<s>
As	O
for	O
the	O
PC	O
,	O
over	O
50	O
different	O
Doom	B-Application
source	O
ports	O
have	O
been	O
developed	O
.	O
</s>
<s>
New	O
features	O
such	O
as	O
OpenGL	B-Application
rendering	O
and	O
scripting	B-Language
allow	O
WADs	O
to	O
alter	O
the	O
gameplay	O
more	O
radically	O
.	O
</s>
<s>
Devoted	O
players	O
have	O
spent	O
years	O
creating	O
speedruns	O
for	O
Doom	B-Application
,	O
competing	O
for	O
the	O
quickest	O
completion	O
times	O
of	O
individual	O
levels	O
and	O
the	O
whole	O
game	O
and	O
sharing	O
knowledge	O
about	O
routes	O
through	O
the	O
levels	O
and	O
how	O
to	O
exploit	O
bugs	B-Error_Name
in	O
the	O
Doom	B-Application
engine	I-Application
for	O
shortcuts	O
.	O
</s>
<s>
Doom	B-Application
was	O
one	O
of	O
the	O
first	O
games	O
to	O
have	O
a	O
speedrunning	O
community	O
,	O
which	O
has	O
remained	O
active	O
up	O
until	O
the	O
present	O
day	O
.	O
</s>
<s>
Achievements	O
include	O
the	O
completion	O
of	O
both	O
Doom	B-Application
and	O
Doom	B-Application
II	I-Application
on	O
the	O
"	O
Ultra-Violence	O
"	O
difficulty	O
setting	O
in	O
less	O
than	O
30minutes	O
each	O
.	O
</s>
<s>
In	O
addition	O
,	O
a	O
few	O
players	O
have	O
also	O
managed	O
to	O
complete	O
Doom	B-Application
II	I-Application
in	O
a	O
single	O
run	O
on	O
the	O
difficulty	O
setting	O
"	O
Nightmare	O
!	O
</s>
<s>
"	O
,	O
on	O
which	O
monsters	O
are	O
more	O
aggressive	O
,	O
launch	O
faster	O
projectiles	O
(	O
or	O
,	O
in	O
the	O
case	O
of	O
the	O
Pinky	O
Demon	B-Operating_System
,	O
simply	O
move	O
faster	O
)	O
,	O
and	O
respawn	O
roughly	O
30seconds	O
after	O
they	O
have	O
been	O
killed	O
(	O
level	O
designer	O
John	O
Romero	O
characterized	O
the	O
idea	O
of	O
such	O
a	O
run	O
as	O
"	O
[	O
just	O
having	O
to	O
be ]	O
impossible	O
"	O
)	O
.	O
</s>
<s>
One	O
notable	O
fan	O
of	O
Doom	B-Application
is	I-Application
Christoph	O
Schneider	O
from	O
the	O
German	O
rock	O
band	O
Rammstein	O
;	O
he	O
uses	O
the	O
stage	O
name	O
"	O
Doom	B-Application
"	O
which	O
was	O
inspired	O
by	O
the	O
video	O
game	O
.	O
</s>
<s>
Schneider	O
's	O
band	O
mate	O
Paul	O
Landers	O
suggested	O
the	O
name	O
"	O
Doom	B-Application
"	O
because	O
they	O
liked	O
the	O
game	O
.	O
</s>
