<s>
Doom	B-General_Concept
WAD	I-General_Concept
is	O
the	O
default	O
format	O
of	O
package	O
files	O
for	O
the	O
video	O
game	O
Doom	B-Application
and	O
its	O
sequel	O
Doom	B-Application
II	I-Application
:	I-Application
Hell	I-Application
on	I-Application
Earth	I-Application
,	O
that	O
contain	O
sprites	O
,	O
levels	O
,	O
and	O
game	O
data	O
.	O
</s>
<s>
Immediately	O
after	O
its	O
release	O
in	O
1993	O
,	O
Doom	B-Application
attracted	O
a	O
sizeable	O
following	O
of	O
players	O
who	O
created	O
their	O
own	O
mods	O
for	O
WAD	O
files	O
—	O
packages	O
containing	O
new	O
levels	O
or	O
graphics	O
—	O
and	O
played	O
a	O
vital	O
part	O
in	O
spawning	O
the	O
mod-making	O
culture	O
which	O
is	O
now	O
commonplace	O
for	O
first-person	O
shooter	O
games	O
.	O
</s>
<s>
Thousands	O
of	O
WADs	O
have	O
been	O
created	O
for	O
Doom	B-Application
,	O
ranging	O
from	O
single	O
custom	O
levels	O
to	O
full	O
original	O
games	O
;	O
most	O
of	O
these	O
can	O
be	O
freely	O
downloaded	O
over	O
the	O
Internet	O
.	O
</s>
<s>
When	O
developing	O
Doom	B-Application
,	O
id	O
Software	O
was	O
aware	O
that	O
many	O
players	O
had	O
tried	O
to	O
create	O
custom	O
levels	O
and	O
other	O
modifications	O
for	O
their	O
previous	O
game	O
,	O
Wolfenstein	B-Application
3D	I-Application
.	O
</s>
<s>
John	O
Carmack	O
,	O
lead	O
programmer	O
at	O
id	O
Software	O
,	O
designed	O
the	O
Doom	B-Application
internals	O
from	O
the	O
ground	O
up	O
to	O
allow	O
players	O
to	O
extend	O
the	O
game	O
.	O
</s>
<s>
The	O
idea	O
of	O
making	O
Doom	B-Application
easily	O
modifiable	O
was	O
primarily	O
backed	O
by	O
Carmack	O
,	O
a	O
well-known	O
supporter	O
of	O
copyleft	B-License
and	O
the	O
hacker	O
ideal	O
of	O
people	O
sharing	O
and	O
building	O
upon	O
each	O
other	O
's	O
work	O
,	O
and	O
by	O
John	O
Romero	O
,	O
who	O
had	O
hacked	O
games	O
in	O
his	O
youth	O
and	O
wanted	O
to	O
allow	O
other	O
gamers	O
to	O
do	O
the	O
same	O
.	O
</s>
<s>
Immediately	O
after	O
the	O
initial	O
shareware	B-License
release	O
of	O
Doom	B-Application
on	O
December	O
10	O
,	O
1993	O
,	O
players	O
began	O
working	O
on	O
various	O
tools	O
to	O
modify	O
the	O
game	O
.	O
</s>
<s>
On	O
January	O
26	O
,	O
1994	O
,	O
Brendon	O
Wyber	O
released	O
the	O
first	O
public	O
domain	O
version	O
of	O
the	O
Doom	B-Application
Editing	O
Utility	O
(	O
DEU	O
)	O
program	O
on	O
the	O
Internet	O
,	O
a	O
program	O
created	O
by	O
Doom	B-Application
fans	O
which	O
made	O
it	O
possible	O
to	O
create	O
entirely	O
new	O
levels	O
.	O
</s>
<s>
It	O
was	O
made	O
possible	O
by	O
Matt	O
Fell	O
's	O
release	O
of	O
the	O
Unofficial	O
Doom	B-Application
specifications	O
.	O
</s>
<s>
Shortly	O
thereafter	O
,	O
Doom	B-Application
players	O
became	O
involved	O
with	O
further	O
enhancing	O
DEU	O
.	O
</s>
<s>
Yadex	O
,	O
a	O
fork	O
of	O
DEU	O
5.21	O
for	O
Unix	B-Application
systems	I-Application
running	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
was	O
later	O
released	O
under	O
the	O
GNU/GPL	B-License
license	O
.	O
</s>
<s>
Carmack	O
additionally	O
released	O
the	O
source	O
code	O
for	O
the	O
utilities	O
used	O
to	O
create	O
the	O
game	O
,	O
but	O
these	O
were	O
programmed	O
in	O
Objective-C	B-Language
,	O
for	O
NeXT	O
workstations	O
,	O
and	O
were	O
therefore	O
not	O
directly	O
usable	O
the	O
mass	O
userbase	O
of	O
IBM	O
PC	O
compatible	O
.	O
</s>
<s>
Jeff	O
Bird	O
is	O
credited	O
with	O
creating	O
the	O
first	O
custom	O
WAD	O
for	O
Doom	B-Application
,	O
called	O
Origwad	O
,	O
on	O
March	O
7	O
,	O
1994	O
.	O
</s>
<s>
Even	O
though	O
WADs	O
modified	O
Doom	B-Application
by	O
replacing	O
graphics	O
and	O
audio	O
,	O
the	O
amount	O
of	O
customization	O
was	O
somewhat	O
limited	O
;	O
much	O
of	O
the	O
game	O
's	O
behavior	O
,	O
including	O
the	O
timing	O
and	O
strength	O
of	O
weapons	O
and	O
enemies	O
,	O
was	O
hard-coded	O
in	O
the	O
Doom	B-Application
executable	B-Application
file	I-Application
and	O
impossible	O
to	O
alter	O
in	O
WADs	O
.	O
</s>
<s>
DeHackEd	B-Application
,	O
a	O
Doom	B-Application
editing	O
program	O
created	O
by	O
Greg	O
Lewis	O
,	O
addressed	O
this	O
by	O
letting	O
users	O
modify	O
parameters	O
inside	O
of	O
the	O
Doom	B-Application
executable	B-Application
itself	O
,	O
allowing	O
for	O
a	O
greater	O
degree	O
of	O
customization	O
.	O
</s>
<s>
Around	O
1994	O
and	O
1995	O
,	O
WADs	O
were	O
distributed	O
primarily	O
through	O
BBSs	O
and	O
via	O
CD	B-Device
collections	O
found	O
in	O
computer	O
shops	O
or	O
bundled	O
together	O
with	O
instruction	O
guides	O
for	O
level	O
creation	O
,	O
while	O
in	O
later	O
years	O
Internet	O
FTP	B-Protocol
servers	O
became	O
the	O
primary	O
method	O
for	O
obtaining	O
these	O
works	O
.	O
</s>
<s>
Although	O
the	O
Doom	B-Application
software	O
license	O
required	O
that	O
no	O
profit	O
be	O
made	O
from	O
custom	O
WADs	O
,	O
and	O
Shawn	O
Green	O
objected	O
to	O
people	O
selling	O
their	O
WADs	O
for	O
money	O
,	O
some	O
WAD	O
sets	O
and	O
shovelware	O
bundles	O
were	O
nonetheless	O
obtainable	O
for	O
a	O
price	O
at	O
certain	O
outlets	O
.	O
</s>
<s>
During	O
this	O
time	O
,	O
id	O
Software	O
was	O
working	O
on	O
their	O
next	O
game	O
,	O
Quake	B-Application
,	O
using	O
new	O
technology	O
,	O
but	O
started	O
projects	O
picking	O
up	O
the	O
most	O
talented	O
WAD	O
makers	O
from	O
the	O
Doom	B-Application
community	O
to	O
create	O
official	O
expansions	O
and	O
to	O
compete	O
with	O
the	O
unauthorized	O
collection	O
CDs	B-Device
.	O
</s>
<s>
The	O
team	O
produced	O
the	O
21	O
Master	B-Application
Levels	I-Application
,	O
which	O
,	O
on	O
December	O
26	O
,	O
1995	O
,	O
were	O
released	O
on	O
a	O
CD	B-Device
along	O
with	O
Maximum	O
Doom	B-Application
,	O
a	O
collection	O
of	O
1,830	O
WADs	O
that	O
had	O
been	O
downloaded	O
from	O
the	O
Internet	O
.	O
</s>
<s>
In	O
1996	O
,	O
Final	B-Application
Doom	I-Application
,	O
a	O
package	O
of	O
two	O
32-level	O
megawads	O
created	O
by	O
TeamTNT	O
,	O
was	O
released	O
as	O
an	O
official	O
id	O
Software	O
product	O
.	O
</s>
<s>
Various	O
first-person	O
shooter	O
games	O
released	O
at	O
the	O
time	O
use	O
the	O
Doom	B-Application
engine	I-Application
under	O
a	O
commercial	O
license	O
from	O
id	O
Software	O
,	O
as	O
such	O
essentially	O
being	O
custom	O
WADs	O
packaged	O
with	O
the	O
Doom	B-Application
engine	I-Application
,	O
such	O
as	O
Hacx	O
:	O
Twitch	O
'	O
n	O
Kill	O
(	O
1997	O
)	O
.	O
</s>
<s>
Tim	O
Willits	O
,	O
who	O
contributed	O
two	O
levels	O
to	O
Master	B-Application
Levels	I-Application
for	I-Application
Doom	I-Application
II	I-Application
,	O
later	O
became	O
the	O
lead	O
designer	O
at	O
id	O
Software	O
.	O
</s>
<s>
Dario	B-Application
Casali	I-Application
,	O
author	O
of	O
a	O
quarter	O
of	O
Final	B-Application
Doom	I-Application
,	O
was	O
hired	O
by	O
Valve	O
to	O
work	O
on	O
Half-Life	B-Application
.	O
</s>
<s>
Sverre	O
Kvernmo	O
,	O
designer	O
of	O
five	O
levels	O
in	O
Master	B-Application
Levels	I-Application
for	I-Application
Doom	I-Application
II	I-Application
and	O
member	O
of	O
TeamTNT	O
,	O
was	O
hired	O
by	O
Ion	O
Storm	O
for	O
Daikatana	B-Application
.	O
</s>
<s>
Iikka	O
Keränen	O
,	O
author	O
of	O
several	O
Doom	B-General_Concept
WADs	I-General_Concept
and	O
later	O
Quake	B-Application
mods	O
,	O
was	O
hired	O
by	O
Ion	O
Storm	O
to	O
create	O
levels	O
for	O
Anachronox	B-Application
and	O
Daikatana	B-Application
,	O
and	O
by	O
Looking	O
Glass	O
Studios	O
to	O
create	O
levels	O
for	O
Thief	B-Application
II	I-Application
:	I-Application
The	I-Application
Metal	I-Application
Age	I-Application
.	O
</s>
<s>
John	O
Anderson	O
(	O
level	O
designer	O
)	O
,	O
also	O
known	O
as	O
"	O
Dr.	O
Sleep	O
"	O
,	O
author	O
of	O
five	O
levels	O
in	O
Master	B-Application
Levels	I-Application
for	I-Application
Doom	I-Application
II	I-Application
and	O
E4M7	O
in	O
The	O
Ultimate	B-Application
Doom	I-Application
,	O
later	O
worked	O
on	O
Blood	B-Application
,	O
Unreal	B-Application
,	O
and	O
Daikatana	B-Application
.	O
</s>
<s>
He	O
later	O
contributed	O
to	O
the	O
Unreal	B-Application
series	O
.	O
</s>
<s>
Around	O
1997	O
,	O
interest	O
in	O
Doom	B-General_Concept
WADs	I-General_Concept
began	O
to	O
decline	O
,	O
as	O
attention	O
was	O
drawn	O
to	O
newer	O
games	O
with	O
more	O
advanced	O
technology	O
and	O
more	O
customizable	O
design	O
,	O
including	O
id	O
Software	O
's	O
own	O
Quake	B-Application
and	O
Quake	B-Application
II	I-Application
.	O
</s>
<s>
On	O
December	O
23	O
,	O
1997	O
,	O
id	O
Software	O
released	O
the	O
source	O
code	O
to	O
the	O
Doom	B-Application
engine	I-Application
,	O
initially	O
under	O
a	O
restrictive	O
license	O
.	O
</s>
<s>
On	O
October	O
3	O
,	O
1999	O
,	O
it	O
was	O
released	O
again	O
under	O
the	O
terms	O
of	O
the	O
GNU	B-License
GPL-2.0-or-later	I-License
.	O
</s>
<s>
With	O
the	O
source	O
code	O
available	O
,	O
it	O
became	O
possible	O
for	O
programmers	O
to	O
modify	O
any	O
aspect	O
of	O
the	O
game	O
,	O
remove	O
technical	O
limitations	O
and	O
bugs	B-Error_Name
,	O
and	O
add	O
entirely	O
new	O
features	O
.	O
</s>
<s>
These	O
engine	O
modifications	O
,	O
or	O
Doom	B-Application
source	O
ports	O
,	O
have	O
since	O
become	O
the	O
target	O
for	O
much	O
of	O
the	O
WAD	O
editing	O
activity	O
,	O
and	O
with	O
the	O
decline	O
of	O
MS-DOS	B-Application
,	O
using	O
a	O
source	O
port	O
became	O
the	O
only	O
feasible	O
way	O
to	O
play	O
Doom	B-Application
for	O
most	O
people	O
.	O
</s>
<s>
Several	O
source	O
ports	O
are	O
in	O
active	O
development	O
,	O
and	O
Doom	B-Application
retains	O
a	O
strong	O
following	O
of	O
WAD	O
creators	O
.	O
</s>
<s>
WADs	O
may	O
have	O
a	O
level	O
pack	O
in	O
the	O
form	O
of	O
an	O
episode	O
,	O
replacing	O
nine	O
levels	O
,	O
and	O
sometimes	O
in	O
the	O
form	O
of	O
a	O
megawad	O
,	O
which	O
replaces	O
15	O
or	O
more	O
levels	O
in	O
the	O
game	O
(	O
27	O
in	O
Doom	B-Application
,	O
32	O
in	O
Doom	B-Application
II	I-Application
,	O
36	O
in	O
The	O
Ultimate	B-Application
Doom	I-Application
)	O
.	O
</s>
<s>
Bloom	B-Application
is	O
a	O
Doom	B-Application
II	I-Application
and	O
Blood	B-Application
crossover	O
released	O
by	O
Bloom	B-Application
Team	O
in	O
2021	O
.	O
</s>
<s>
Eternal	O
Doom	B-Application
is	I-Application
a	O
32-level	O
megawad	O
for	O
Doom	B-Application
II	I-Application
created	O
by	O
Team	O
Eternal	O
and	O
TeamTNT	O
.	O
</s>
<s>
Eternal	O
Doom	B-Application
received	O
media	O
attention	O
in	O
2020	O
,	O
when	O
through	O
further	O
modding	O
,	O
it	O
was	O
played	O
through	O
Doom	B-Application
Eternal	I-Application
.	O
</s>
<s>
Going	O
Down	O
is	O
a	O
32-level	O
megawad	O
for	O
Doom	B-Application
II	I-Application
released	O
in	O
2013	O
,	O
and	O
a	O
winner	O
in	O
that	O
year	O
's	O
Cacowards	O
.	O
</s>
<s>
Icarus	O
:	O
Alien	O
Vanguard	O
is	O
a	O
32-level	O
megawad	O
for	O
Doom	B-Application
II	I-Application
created	O
by	O
TeamTNT	O
and	O
released	O
on	O
March	O
22	O
,	O
1996	O
.	O
</s>
<s>
It	O
was	O
developed	O
as	O
a	O
freeware	B-License
release	O
after	O
TNT	B-Application
:	I-Application
Evilution	I-Application
was	O
picked	O
up	O
by	O
id	O
Software	O
to	O
be	O
released	O
as	O
part	O
of	O
Final	B-Application
Doom	I-Application
.	O
</s>
<s>
Memento	O
Mori	O
is	O
a	O
32-level	O
megawad	O
for	O
Doom	B-Application
II	I-Application
created	O
by	O
two	O
members	O
of	O
The	O
Innocent	O
Crew	O
,	O
Denis	O
and	O
Thomas	O
Möller	O
,	O
along	O
with	O
other	O
authors	O
,	O
including	O
Tom	O
Mustaine	O
and	O
both	O
Dario	O
and	O
Milo	O
Casali	O
.	O
</s>
<s>
Requiem	O
is	O
a	O
32-level	O
megawad	O
for	O
Doom	B-Application
II	I-Application
created	O
by	O
the	O
same	O
people	O
that	O
worked	O
on	O
the	O
previously	O
released	O
Memento	O
Mori	O
series	O
,	O
in	O
addition	O
to	O
some	O
new	O
mappers	O
that	O
worked	O
specifically	O
on	O
this	O
project	O
.	O
</s>
<s>
After	O
the	O
positive	O
response	O
,	O
he	O
released	O
Sigil	B-Application
,	O
a	O
complete	O
9-level	O
episode	O
,	O
in	O
May	O
2019	O
.	O
</s>
<s>
Action	O
Doom	B-Application
2	I-Application
:	O
Urban	O
Brawl	O
is	O
a	O
2008	O
indie	O
game	O
developed	O
by	O
"	O
Scuba	O
Steve	O
"	O
Browning	O
with	O
the	O
ZDoom	O
source	O
port	O
.	O
</s>
<s>
The	O
game	O
features	O
cel-shaded	O
graphics	O
reminiscent	O
of	O
a	O
comic	O
book	O
,	O
and	O
is	O
played	O
in	O
the	O
style	O
of	O
a	O
beat	B-Application
'	I-Application
em	I-Application
up	I-Application
,	O
with	O
some	O
gunplay	O
present	O
as	O
well	O
.	O
</s>
<s>
Batman	B-General_Concept
Doom	B-Application
is	I-Application
a	O
32-level	O
total	O
conversion	O
created	O
by	O
ACE	O
Team	O
Software	O
and	O
released	O
in	O
April	O
1999	O
.	O
</s>
<s>
It	O
contains	O
modified	O
game	O
behavior	O
along	O
with	O
new	O
weapons	O
,	O
items	O
,	O
and	O
characters	O
from	O
the	O
world	O
of	O
the	O
comic	O
book	O
superhero	O
Batman	B-General_Concept
.	O
</s>
<s>
Chex	B-Application
Quest	I-Application
is	O
a	O
5-level	O
total	O
conversion	O
released	O
in	O
1996	O
by	O
Digital	O
Café	O
so	O
that	O
Doom	B-Application
could	O
be	O
approved	O
for	O
younger	O
audiences	O
.	O
</s>
<s>
This	O
was	O
originally	O
packaged	O
in	O
Chex	O
cereal	O
boxes	O
as	O
a	O
prize	O
,	O
though	O
Chex	B-Application
Quest	I-Application
was	O
later	O
put	O
up	O
as	O
freeware	B-License
on	O
the	O
Internet	O
after	O
the	O
promotion	O
ended	O
.	O
</s>
<s>
Chex	B-Application
Quest	I-Application
received	O
two	O
sequels	O
,	O
Chex	B-Application
Quest	I-Application
2	O
:	O
Flemoids	O
Take	O
Chextropolis	O
and	O
Chex	B-Application
Quest	I-Application
3	O
,	O
released	O
in	O
1997	O
and	O
2008	O
,	O
respectively	O
,	O
both	O
of	O
which	O
contained	O
five	O
levels	O
and	O
were	O
released	O
as	O
freeware	B-License
.	O
</s>
<s>
Doom	B-Application
64	I-Application
:	O
Retribution	O
is	O
a	O
remake	O
of	O
Doom	B-Application
64	I-Application
,	O
the	O
Nintendo	B-Operating_System
64	I-Operating_System
version	O
of	O
Doom	B-Application
,	O
which	O
differs	O
drastically	O
from	O
its	O
DOS	O
version	O
.	O
</s>
<s>
Doom	B-Application
64	I-Application
:	O
Retribution	O
contains	O
different	O
levels	O
,	O
graphics	O
,	O
and	O
audio	O
based	O
on	O
the	O
Nintendo	B-Operating_System
64	I-Operating_System
game	O
.	O
</s>
<s>
Grezzo	B-Application
2	I-Application
is	O
a	O
2012	O
total	O
conversion	O
developed	O
by	O
Italian	O
game	O
designer	O
Nicola	O
Piro	O
,	O
notable	O
for	O
plagiarizing	O
other	O
games	O
and	O
Doom	B-Application
mods	I-Application
,	O
and	O
for	O
its	O
vulgar	O
,	O
blasphemous	O
content	O
.	O
</s>
<s>
Sonic	O
Robo	O
Blast	O
2	O
is	O
a	O
Doom	B-Application
modification	O
that	O
uses	O
the	O
Doom	B-Application
Legacy	O
source	O
port	O
to	O
completely	O
change	O
the	O
game	O
from	O
a	O
first-person	O
shooter	O
to	O
a	O
third-person	O
platformer	O
based	O
on	O
Sonic	O
the	O
Hedgehog	O
.	O
</s>
<s>
Void	O
is	O
a	O
single-level	O
modification	O
based	O
on	O
the	O
2000	O
game	O
American	B-Application
McGee	I-Application
's	I-Application
Alice	I-Application
,	O
which	O
was	O
itself	O
made	O
by	O
former	O
id	O
Software	O
employee	O
American	O
McGee	O
.	O
</s>
<s>
D	O
!	O
Zone	O
–	O
Created	O
by	O
WizardWorks	O
,	O
an	O
expansion	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>
Origwad	O
–	O
Created	O
by	O
Jeff	O
Bird	O
and	O
released	O
on	O
March	O
7	O
,	O
1994	O
,	O
it	O
is	O
notable	O
for	O
being	O
the	O
first	O
custom	O
WAD	O
to	O
be	O
released	O
for	O
Doom	B-Application
.	O
</s>
<s>
The	O
Harris	O
levels	O
–	O
Doom	B-Application
and	O
Doom	B-Application
II	I-Application
levels	O
created	O
by	O
Eric	O
Harris	O
,	O
one	O
of	O
the	O
two	O
perpetrators	O
of	O
the	O
Columbine	O
High	O
School	O
massacre	O
,	O
believed	O
to	O
have	O
surfaced	O
on	O
the	O
Internet	O
in	O
1996	O
or	O
1997	O
,	O
but	O
were	O
taken	O
down	O
by	O
the	O
FBI	O
after	O
the	O
1999	O
massacre	O
.	O
</s>
<s>
Downloads	O
for	O
the	O
levels	O
Deathmatching	O
in	O
Bricks	O
(	O
BRICKS.WAD	O
)	O
,	O
Hockey.wad	O
(	O
HOCKEY.WAD	O
)	O
,	O
KILLER	O
(	O
KILLER.WAD	O
)	O
,	O
Mortal	O
Kombat	O
Doom	B-Application
(	O
FIGHTME.WAD	O
)	O
,	O
Outdoors	O
(	O
outdoors.wad	O
)	O
,	O
Station	O
(	O
STATION.WAD	O
)	O
,	O
and	O
UAC	O
Labs	O
(	O
UACLABS.WAD	O
)	O
have	O
been	O
found	O
in	O
the	O
years	O
since	O
.	O
</s>
<s>
Its	O
creator	O
,	O
B.P.R.D	O
,	O
created	O
multiple	O
sequels	O
,	O
and	O
a	O
version	O
of	O
Nuts	O
was	O
made	O
in	O
Dusk	B-Application
.	O
</s>
<s>
Lilith	O
–	O
A	O
wad	O
created	O
in	O
2017	O
that	O
uses	O
glitches	B-Error_Name
in	O
the	O
Zdoom	O
sourceport	O
to	O
create	O
graphical	O
and	O
musical	O
distortion	O
,	O
and	O
changes	O
in	O
enemy	O
behavior	O
,	O
resulting	O
in	O
a	O
"	O
glitchcore	O
nightmare.	O
"	O
</s>
<s>
Freedoom	O
is	O
a	O
project	O
aiming	O
to	O
create	O
a	O
free	B-Application
replacement	O
(	O
modified	O
BSD	B-Operating_System
License	I-Operating_System
)	O
for	O
the	O
set	O
of	O
graphics	O
,	O
music	O
,	O
sound	O
effects	O
,	O
and	O
levels	O
(	O
and	O
miscellaneous	O
other	O
resources	O
)	O
used	O
by	O
Doom	B-Application
.	O
</s>
<s>
Since	O
the	O
Doom	B-Application
engine	I-Application
is	O
free	B-Application
software	I-Application
,	O
it	O
can	O
be	O
distributed	O
along	O
with	O
the	O
new	O
resources	O
,	O
in	O
effect	O
providing	O
a	O
full	O
game	O
that	O
is	O
free	B-Application
and	O
with	O
full	O
third	O
party	O
WAD	O
.	O
</s>
<s>
Freedoom	O
does	O
not	O
require	O
any	O
source	O
port	O
to	O
run	O
,	O
and	O
can	O
run	O
on	O
any	O
limit-removing	O
source	O
port	O
of	O
Doom	B-Application
.	O
</s>
<s>
A	O
similar	O
project	O
,	O
Blasphemer	O
,	O
aims	O
to	O
create	O
a	O
complete	O
free	B-Application
version	O
of	O
Heretic	B-Application
,	O
but	O
is	O
less	O
fully	O
developed	O
than	O
Freedoom	O
.	O
</s>
<s>
Zauberer	O
was	O
also	O
been	O
initiated	O
for	O
Hexen	B-Application
.	O
</s>
<s>
Many	O
level	O
editors	O
are	O
available	O
for	O
Doom	B-Application
.	O
</s>
<s>
The	O
original	O
Doom	B-Application
Editing	O
Utility	O
(	O
DEU	O
)	O
was	O
ported	O
to	O
a	O
number	O
of	O
operating	B-General_Concept
systems	I-General_Concept
,	O
but	O
lost	O
significance	O
over	O
time	O
;	O
many	O
modern	O
Doom	B-Application
editors	O
still	O
have	O
their	O
roots	O
in	O
DEU	O
and	O
its	O
editing	O
paradigm	O
,	O
including	O
DETH	O
,	O
DeePsea	O
,	O
Linux	B-Application
Doom	B-Application
Editor	O
,	O
and	O
Yadex	O
and	O
its	O
fork	O
Eureka	O
.	O
</s>
<s>
Other	O
level	O
editors	O
include	O
WadAuthor	O
,	O
Doom	B-Application
Builder	O
(	O
released	O
in	O
January	O
2003	O
)	O
,	O
and	O
Doom	B-Application
Builder	O
2	O
(	O
released	O
in	O
May	O
2009	O
as	O
the	O
successor	O
to	O
Doom	B-Application
Builder	O
)	O
.	O
</s>
<s>
Some	O
Doom	B-Application
level	O
editors	O
,	O
such	O
as	O
Doom	B-Application
Builder	O
and	O
Doom	B-Application
Builder	O
2	O
,	O
feature	O
a	O
3D	O
editing	O
mode	O
.	O
</s>
<s>
GZDoom	O
Builder	O
is	O
also	O
discontinued	O
and	O
is	O
now	O
being	O
maintained	O
as	O
Ultimate	B-Application
Doom	I-Application
Builder	O
.	O
</s>
<s>
Many	O
specialized	O
Doom	B-Application
editors	O
are	O
used	O
to	O
modify	O
graphics	O
and	O
audio	O
lumps	O
,	O
such	O
asXWE	O
,	O
SLADE	O
,	O
Wintex	O
,	O
and	O
SLumpEd	O
.	O
</s>
<s>
The	O
DeHackEd	B-Application
executable	B-Application
patching	O
utility	O
modifies	O
monsters	O
,	O
items	O
,	O
and	O
weapon	O
behavior	O
.	O
</s>
<s>
In	O
ZDoom	O
,	O
users	O
can	O
create	O
new	O
monsters	O
,	O
weapons	O
,	O
and	O
items	O
through	O
a	O
scripting	O
language	O
called	O
DECORATE	O
,	O
made	O
to	O
address	O
many	O
of	O
the	O
shortcomings	O
of	O
DeHackEd	B-Application
,	O
such	O
as	O
not	O
being	O
able	O
to	O
add	O
new	O
objects	O
,	O
and	O
not	O
being	O
able	O
to	O
deviate	O
far	O
from	O
the	O
behavior	O
of	O
the	O
original	O
weapons	O
and	O
monsters	O
.	O
</s>
<s>
In	O
Quake	B-Application
,	O
WAD	O
files	O
were	O
replaced	O
with	O
PAK	O
files	O
.	O
</s>
<s>
WAD	O
files	O
still	O
remain	O
in	O
Quake	B-Application
files	O
,	O
though	O
their	O
use	O
is	O
limited	O
to	O
textures	O
.	O
</s>
<s>
Since	O
WAD2	O
and	O
WAD3	O
use	O
a	O
slightly	O
larger	O
directory	O
structure	O
,	O
they	O
are	O
incompatible	O
with	O
Doom	B-Application
.	O
</s>
