<s>
An	O
open-source	B-Application
video	I-Application
game	I-Application
,	O
or	O
simply	O
an	O
open-source	B-Application
game	I-Application
,	O
is	O
a	O
video	O
game	O
whose	O
source	O
code	O
is	O
open-source	B-License
.	O
</s>
<s>
They	O
are	O
often	O
freely	O
distributable	O
and	O
sometimes	O
cross-platform	B-Operating_System
compatible	O
.	O
</s>
<s>
Not	O
all	O
open-source	B-Application
games	I-Application
are	O
free	B-Application
software	I-Application
;	O
some	O
open-source	B-Application
games	I-Application
contain	O
proprietary	B-Application
non-free	O
content	O
.	O
</s>
<s>
Open-source	B-Application
games	I-Application
that	O
are	O
free	B-Application
software	I-Application
and	O
contain	O
exclusively	O
free	O
content	O
conform	O
to	O
DFSG	B-License
,	O
free	B-Application
culture	I-Application
,	O
and	O
open	O
content	O
and	O
are	O
sometimes	O
called	O
free	B-Application
games	I-Application
.	O
</s>
<s>
Many	O
Linux	B-Application
distributions	I-Application
require	O
for	O
inclusion	O
that	O
the	O
game	O
content	O
is	O
freely	O
redistributable	O
,	O
freeware	B-License
or	O
commercial	O
restriction	O
clauses	O
are	O
prohibited	O
.	O
</s>
<s>
In	O
general	O
,	O
open-source	B-Application
games	I-Application
are	O
developed	O
by	O
relatively	O
small	O
groups	O
of	O
people	O
in	O
their	O
free	O
time	O
,	O
with	O
profit	O
not	O
being	O
the	O
main	O
focus	O
.	O
</s>
<s>
Many	O
open-source	B-Application
games	I-Application
are	O
volunteer-run	O
projects	O
,	O
and	O
as	O
such	O
,	O
developers	O
of	O
free	B-Application
games	I-Application
are	O
often	O
hobbyists	O
and	O
enthusiasts	O
.	O
</s>
<s>
The	O
consequence	O
of	O
this	O
is	O
that	O
open-source	B-Application
games	I-Application
often	O
take	O
longer	O
to	O
mature	O
,	O
are	O
less	O
common	O
and	O
often	O
lack	O
the	O
production	O
value	O
of	O
commercial	O
titles	O
.	O
</s>
<s>
In	O
the	O
past	O
(	O
before	O
the	O
2000s	O
)	O
a	O
challenge	O
to	O
build	B-Application
high-quality	O
content	O
for	O
games	O
was	O
the	O
missing	O
availability	O
or	O
the	O
excessive	O
price	O
for	O
tools	O
like	O
3D	O
modeller	O
or	O
toolsets	O
for	O
level	O
design	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
this	O
changed	O
and	O
availability	O
of	O
open-source	B-Application
tools	I-Application
like	O
Blender	B-Application
,	O
game	O
engines	O
and	O
libraries	O
drove	O
open	B-License
source	I-License
and	O
independent	O
video	O
gaming	O
.	O
</s>
<s>
FLOSS	B-License
game	O
engines	O
,	O
like	O
the	O
Godot	B-Application
game	O
engine	O
,	O
as	O
well	O
as	O
libraries	O
,	O
like	O
SDL	B-Operating_System
,	O
are	O
increasingly	B-Application
common	I-Application
in	O
game	O
development	O
,	O
even	O
proprietary	B-Application
ones	O
.	O
</s>
<s>
Given	O
that	O
game	O
art	O
is	O
not	O
considered	O
software	O
,	O
there	O
is	O
debate	O
about	O
the	O
philosophical	O
or	O
ethical	O
obstacles	O
in	O
selling	O
a	O
game	O
where	O
its	O
art	O
is	O
proprietary	B-Application
but	O
the	O
entire	O
source	O
code	O
is	O
free	B-Application
software	I-Application
.	O
</s>
<s>
Some	O
of	O
the	O
open-source	B-Application
game	I-Application
projects	O
are	O
based	O
on	O
formerly	O
proprietary	B-Application
games	O
,	O
whose	O
source	O
code	O
was	O
released	O
as	O
open-source	B-Application
software	I-Application
,	O
while	O
the	O
game	O
content	O
(	O
such	O
as	O
graphics	O
,	O
audio	O
and	O
levels	O
)	O
may	O
or	O
may	O
not	O
be	O
under	O
a	O
free	O
license	O
.	O
</s>
<s>
Examples	O
include	O
Warzone	B-Application
2100	I-Application
(	O
a	O
real-time	O
strategy	O
game	O
)	O
and	O
Micropolis	B-Application
(	O
a	O
city-building	O
simulator	O
based	O
on	O
the	O
SimCity	B-Application
source	O
code	O
)	O
.	O
</s>
<s>
Advantage	O
of	O
such	O
continuation	O
projects	O
is	O
that	O
these	O
games	O
are	O
already	O
"	O
complete	O
"	O
as	O
graphic	O
and	O
audio	O
content	O
is	O
available	O
,	O
and	O
therefore	O
the	O
open-source	B-License
authors	O
can	O
focus	O
on	O
porting	O
,	O
fixing	O
bugs	O
or	O
modding	O
the	O
games	O
.	O
</s>
<s>
In	O
a	O
2004	O
article	O
,	O
Adam	O
Geitgey	O
questioned	O
the	O
compatibility	O
of	O
the	O
open-source	B-License
culture	O
with	O
respect	O
to	O
the	O
game	O
development	O
process	O
.	O
</s>
<s>
He	O
suggested	O
that	O
perceived	O
open-source	B-Application
development	I-Application
advantages	O
do	O
not	O
work	O
for	O
games	O
because	O
users	O
move	O
on	O
to	O
new	O
games	O
relatively	O
quickly	O
and	O
so	O
do	O
not	O
give	O
back	O
to	O
the	O
project	O
.	O
</s>
<s>
While	O
Linux	B-Application
operates	O
on	O
the	O
open-source	B-License
philosophy	O
,	O
this	O
may	O
not	O
benefit	O
game	O
development	O
.	O
</s>
<s>
As	O
of	O
September	O
2015	O
,	O
the	O
Steam	B-Application
gaming	O
service	O
has	O
1,500	O
games	O
available	O
on	O
Linux	B-Application
,	O
compared	O
to	O
2,323	O
games	O
for	O
Mac	B-Device
and	O
6,500	O
Windows	B-Application
games	O
.	O
</s>
<s>
Just	O
as	O
in	O
most	O
other	O
forms	O
of	O
software	O
,	O
free	B-Application
software	I-Application
was	O
an	O
unconscious	O
occurrence	O
during	O
the	O
creation	O
of	O
early	O
computer	O
games	O
,	O
particularly	O
for	O
earlier	O
Unix	B-Application
games	O
.	O
</s>
<s>
These	O
are	O
mostly	O
arcade	O
conversions	O
,	O
parlour	O
games	O
,	O
and	O
text	O
adventures	O
using	B-Language
libraries	O
like	O
curses	B-Device
.	O
</s>
<s>
A	O
notable	O
example	O
of	O
this	O
is	O
the	O
"	O
BSD	B-Operating_System
Games	O
"	O
,	O
a	O
collection	O
of	O
interactive	O
fiction	O
and	O
other	O
text-mode	O
titles	O
.	O
</s>
<s>
Game	O
fan	O
communities	O
such	O
as	O
the	O
modding	O
community	O
do	O
include	O
some	O
aspects	O
of	O
free	B-Application
software	I-Application
,	O
such	O
as	O
sharing	O
mods	O
across	O
community	O
sites	O
,	O
sometimes	O
with	O
free	O
to	O
use	O
media	O
made	O
for	O
the	O
modification	O
.	O
</s>
<s>
With	O
the	O
rise	O
of	O
proprietary	B-Application
software	I-Application
in	O
the	O
mid	O
to	O
late	O
1980s	O
,	O
games	O
became	O
more	O
and	O
more	O
proprietary	B-Application
.	O
</s>
<s>
However	O
,	O
this	O
also	O
led	O
to	O
the	O
first	O
deliberately	O
free	B-Application
games	I-Application
such	O
as	O
GNU	O
Backgammon	B-Application
,	O
GNU	B-Application
Chess	I-Application
,	O
GNU	B-Application
Go	I-Application
,	O
and	O
GNU	O
Shogi	O
of	O
the	B-Application
GNU	I-Application
Project	I-Application
established	O
in	O
1983	O
,	O
part	O
of	O
whose	O
goal	O
is	O
to	O
create	O
a	O
complete	O
free	B-Application
software	I-Application
system	O
,	O
games	O
included	O
.	O
</s>
<s>
More	O
advanced	O
free	O
gaming	O
projects	O
emerged	O
,	O
such	O
as	O
Moria	B-Device
and	O
its	O
descendant	O
Angband	B-Application
,	O
Hack	B-Application
and	O
its	O
derivatives	O
NetHack	B-Application
and	O
Slash'EM	B-Application
,	O
in	O
addition	O
to	O
Xtrek	O
successor	O
Netrek	B-Application
,	O
variants	O
of	O
robots	B-Device
,	O
and	O
adventure	O
game	O
Dunnet	B-Operating_System
,	O
which	O
has	O
been	O
included	O
with	O
GNU	B-Application
Emacs	I-Application
since	O
1994	O
among	O
others	O
.	O
</s>
<s>
Still	O
developed	O
and	O
played	O
today	O
,	O
front-ends	O
for	O
frameworks	O
such	O
as	O
X11	B-Operating_System
,	O
SDL	B-Operating_System
,	O
GTK	B-Application
and	O
Qt	B-Language
,	O
plus	O
fuller	O
featured	O
variants	O
such	O
as	O
Iso-Angband	O
,	O
glHack	O
and	O
Vulture	B-Application
's	I-Application
Eye	I-Application
have	O
kept	O
the	O
games	O
accessible	O
.	O
</s>
<s>
Roguelikes	O
have	O
continued	O
to	O
be	O
produced	O
,	O
including	O
Cataclysm	B-Application
:	I-Application
Dark	I-Application
Days	I-Application
Ahead	I-Application
,	O
Tales	B-Language
of	I-Language
Maj'Eyal	I-Language
,	O
HyperRogue	B-Language
,	O
DRL	B-Language
,	O
Isleward	O
,	O
Egoboo	B-Application
,	O
S.C.O.U.R.G.E.	O
,	O
Shattered	O
Pixel	O
Dungeon	O
,	O
as	O
well	O
as	O
Linley	B-Language
's	I-Language
Dungeon	I-Language
Crawl	I-Language
and	O
its	O
offspring	O
Dungeon	B-Language
Crawl	I-Language
Stone	I-Language
Soup	I-Language
.	O
</s>
<s>
The	O
source	O
code	O
to	O
the	O
original	O
Rogue	B-Application
was	O
released	O
under	O
the	O
BSD	B-Operating_System
license	I-Operating_System
in	O
1986	O
.	O
</s>
<s>
More	O
complicated	O
games	O
utilizing	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
for	O
graphics	O
started	O
to	O
appear	O
,	O
most	O
beginning	O
with	O
the	O
signature	O
letter	O
X	B-Operating_System
.	O
</s>
<s>
These	O
included	O
XAsteroids	B-Application
,	O
XBattle	O
,	O
XBoing	B-Application
,	O
X-Bomber	B-Application
,	O
XConq	B-Application
,	O
XDigger	B-Application
,	O
XEmeraldia	B-Device
,	O
XGalaga	B-Application
,	O
XGammon	B-Application
,	O
XLander	B-Application
,	O
XLife	O
,	O
XMahjong	B-Application
,	O
XMine	B-Application
,	O
XSoldier	O
,	O
XPilot	B-Language
,	O
XRobots	B-Device
,	O
XRubiks	O
,	O
XShogi	O
,	O
XScavenger	B-Application
,	O
XTris	B-Device
,	O
XTron	B-Application
,	O
and	O
XTic	O
.	O
</s>
<s>
XBill	B-Application
is	O
notable	O
as	O
one	O
of	O
the	O
earliest	O
free	O
gaming	O
titles	O
to	O
feature	O
an	O
activist	O
theme	O
of	O
halting	O
proprietary	B-Application
software	I-Application
adoption	O
,	O
later	O
echoed	O
in	O
titles	O
such	O
as	O
Virus	B-Application
Killer	I-Application
,	O
Defendguin	O
and	O
FreedroidRPG	O
.	O
</s>
<s>
XEvil	O
followed	O
the	O
development	O
cycle	O
of	O
many	O
early	O
pieces	O
of	O
free	B-Application
software	I-Application
,	O
having	O
originally	O
been	O
developed	O
as	O
a	O
university	O
project	O
on	O
the	O
Project	B-Operating_System
Athena	I-Operating_System
network	O
,	O
although	O
it	O
was	O
freeware	B-License
for	O
a	O
while	O
.	O
</s>
<s>
XTux	O
was	O
also	O
an	O
early	O
deathmatch	O
game	O
for	O
Linux	B-Application
,	O
featuring	O
various	O
free	B-Application
software	I-Application
mascots	O
,	O
a	O
theme	O
that	O
would	O
continue	O
to	O
be	O
revisited	O
.	O
</s>
<s>
Rocks'n'Diamonds	B-Language
is	O
another	O
earlier	O
free	B-Application
software	I-Application
game	O
,	O
and	O
one	O
of	O
the	O
first	O
for	O
Linux	B-Application
.	O
</s>
<s>
The	O
Freeciv	B-Application
project	O
was	O
started	O
in	O
1995	O
and	O
gave	O
rise	O
to	O
another	O
new	O
style	O
of	O
free	B-Application
game	I-Application
development	O
.	O
</s>
<s>
Similar	O
to	O
the	O
cooperative	O
nature	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
development	O
,	O
Freeciv	B-Application
was	O
extended	O
by	O
many	O
volunteers	O
,	O
rather	O
than	O
only	O
one	O
or	O
two	O
authors	O
.	O
</s>
<s>
Freeciv	B-Application
also	O
proved	O
to	O
be	O
one	O
of	O
the	O
earliest	O
very	O
popular	O
free	B-Application
software	I-Application
games	I-Application
,	O
and	O
was	O
among	O
the	O
first	O
to	O
be	O
included	O
with	O
Linux	B-Application
distributions	I-Application
,	O
a	O
system	O
commonly	O
known	O
now	O
as	O
a	O
source	O
of	O
peer	O
review	O
or	O
selection	O
of	O
quality	O
for	O
free	O
gaming	O
projects	O
.	O
</s>
<s>
Magazines	O
,	O
news	O
sources	O
and	O
websites	O
have	O
also	O
started	O
noting	O
free	B-Application
games	I-Application
,	O
often	O
in	O
listings	O
.	O
</s>
<s>
Freeciv	B-Application
and	O
other	O
archetypes	O
have	O
led	O
to	O
the	O
development	O
of	O
many	O
other	O
clones	O
of	O
popular	O
proprietary	B-Application
games	O
.	O
</s>
<s>
Lincity	B-Application
was	O
also	O
started	O
in	O
1995	O
,	O
despite	O
there	O
having	O
been	O
a	O
Unix	B-Application
version	O
of	O
its	O
namesake	B-Application
officially	O
released	O
by	O
DUX	O
Software	O
in	O
1990	O
.	O
</s>
<s>
Beyond	O
directly	O
tying	O
to	O
the	O
operating	O
system	O
,	O
various	O
free	B-Application
game	I-Application
development	O
frameworks	O
emerged	O
starting	O
with	O
Allegro	B-Language
in	O
1990	O
,	O
SDL	B-Operating_System
in	O
1998	O
,	O
ClanLib	B-Language
in	O
1999	O
,	O
OpenAL	B-Application
in	O
2000	O
,	O
SFML	B-Language
in	O
2007	O
,	O
as	O
well	O
as	O
SDL	B-Operating_System
2	O
and	O
Raylib	B-Language
in	O
2013	O
.	O
</s>
<s>
The	O
GNU	B-Application
Image	I-Application
Manipulation	I-Application
Program	I-Application
,	O
MyPaint	B-Language
,	O
Kirta	O
,	O
Inkscape	B-Application
,	O
Synfig	B-Language
,	O
Pencil2D	B-Language
,	O
Audacity	B-Language
,	O
Rosegarden	B-Language
,	O
OpenShot	B-Application
,	O
Kdenlive	B-Language
,	O
Pitivi	B-Application
,	O
Blender	B-Application
,	O
MakeHuman	B-Language
,	O
MM3D	B-Application
,	O
and	O
other	O
applications	O
have	O
provided	O
an	O
entire	O
open	B-License
source	I-License
toolchain	O
for	O
creative	O
projects	O
.	O
</s>
<s>
Proprietary	B-Application
games	O
such	O
as	O
Doom	B-Application
and	O
Descent	B-Application
brought	O
in	O
the	O
age	O
of	O
three-dimensional	O
games	O
in	O
the	O
early	O
to	O
mid	O
1990s	O
,	O
and	O
free	B-Application
games	I-Application
started	O
to	O
make	O
the	O
switch	O
themselves	O
.	O
</s>
<s>
Tuxedo	O
T	O
.	O
Penguin	O
:	O
A	O
Quest	O
for	O
Herring	O
by	O
Steve	O
Baker	O
,	O
a	O
game	O
featuring	O
the	O
Linux	B-Application
mascot	I-Application
Tux	B-Application
and	O
introducing	O
the	O
PLIB	O
library	O
,	O
was	O
an	O
early	O
example	O
of	O
a	O
three-dimensional	O
free	B-Application
software	I-Application
game	O
.	O
</s>
<s>
He	O
and	O
his	O
son	O
Oliver	O
would	O
later	O
create	O
other	O
popular	O
3D	O
free	B-Application
games	I-Application
and	O
clones	O
such	O
as	O
TuxKart	B-Application
and	O
contribute	O
to	O
those	O
by	O
other	O
developers	O
such	O
as	O
Tux	B-Application
Racer	I-Application
.	O
</s>
<s>
BZFlag	B-Language
pre-dates	O
all	O
of	O
these	O
,	O
inspired	O
by	O
Battlezone	B-Application
and	O
started	O
in	O
1992	O
and	O
released	O
in	O
1993	O
.	O
</s>
<s>
FlightGear	B-Language
,	O
YSFlight	B-Application
,	O
and	O
GL-117	O
are	O
also	O
good	O
examples	O
of	O
original	O
3D	O
games	O
,	O
first	O
started	O
in	O
1997	O
,	O
1999	O
and	O
2003	O
respectively	O
(	O
and	O
the	O
latter	O
eventually	O
forked	O
as	O
Linux	B-Application
Air	O
Combat	O
)	O
,	O
especially	O
noting	O
that	O
they	O
are	O
not	O
first-person	O
shooters	O
but	O
flight	B-Application
simulators	I-Application
;	O
Danger	B-Application
from	I-Application
the	I-Application
Deep	I-Application
meanwhile	O
simulates	O
submarines	O
.	O
</s>
<s>
The	O
OpenGL	B-Application
specification	O
provided	O
a	O
foundation	O
for	O
hardware	B-General_Concept
acceleration	I-General_Concept
since	O
1992	O
,	O
primarily	O
through	O
the	O
free	O
Mesa	B-Application
implementation	O
since	O
1995	O
,	O
and	O
later	O
complimented	O
by	O
Vulkan	B-Application
since	O
2016	O
.	O
</s>
<s>
The	O
Direct3D	B-Application
API	O
has	O
also	O
been	O
made	O
available	O
on	O
free	O
operating	O
systems	O
via	O
compatibility	B-General_Concept
layers	I-General_Concept
such	O
as	O
WineD3D	O
and	O
DXKV	O
.	O
</s>
<s>
The	O
Glide	B-Operating_System
API	I-Operating_System
was	O
also	O
made	O
open	B-License
source	I-License
following	O
the	O
dissolution	O
of	O
3dfx	O
in	O
2002	O
.	O
</s>
<s>
The	O
Genesis3D	O
engine	O
project	O
,	O
Crystal	B-Language
Space	I-Language
and	O
Cube	B-Application
also	O
spawned	O
other	O
3D	O
free	B-Application
software	I-Application
engines	O
and	O
games	O
,	O
later	O
joined	O
by	O
the	O
likes	O
of	O
Cocos3D	B-Application
,	O
Retribution	O
,	O
Horde3D	B-Operating_System
,	O
Delta3D	B-Language
,	O
Bork3D	B-Application
,	O
Dim3	B-Operating_System
,	O
Urho3D/U3D	O
,	O
Delta	O
Engine	O
,	O
Neutron	O
,	O
Lescegra	O
,	O
Raydium	O
,	O
Drome	O
Engine	O
,	O
Spineless	O
,	O
Vanda	O
,	O
Linderdaum	O
,	O
Lumix	O
,	O
Toy	O
,	O
ezEngine	O
,	O
WickedEngine	O
,	O
Limon	O
,	O
Banshee	O
,	O
Armory	O
,	O
Esenthel	O
,	O
Flax	O
,	O
and	O
the	O
G3D	O
Innovation	O
Engine	O
.	O
</s>
<s>
Engines	O
even	O
exist	O
for	O
high-level	B-Language
programming	I-Language
languages	I-Language
such	O
as	O
Python	B-Language
(	O
Pyglet	B-Library
,	O
PyOpenGL	O
,	O
Soya3D	B-Application
,	O
PyUnity	O
,	O
PyZOE	O
)	O
,	O
Pascal	B-Application
(	O
GLScene	B-Application
,	O
Castle	O
,	O
nxPascal	O
,	O
ZenGL	O
)	O
,	O
Lua	B-Language
(	O
LÖVR	O
,	O
LÖVE3D	O
)	O
,	O
Rust	B-Application
(	O
Amethyst	O
,	O
Bevy	O
,	O
Fyrox	O
,	O
Piston	O
)	O
,	O
Java	B-Language
(	O
libGDX	B-Library
,	O
Jake2	B-Language
,	O
jMonkeyEngine	B-Application
,	O
Env3D	O
)	O
,	O
Kotlin	B-Language
(	O
KorGE	O
,	O
MiniGDX	O
)	O
,	O
Go	B-Application
(	O
Azul3D	O
,	O
G3N	O
)	O
,	O
Gambas	B-Language
(	O
PS	O
Tech	O
)	O
FreeBASIC	B-Language
(	O
OpenB3D	O
)	O
in	O
addition	O
to	O
ActionScript	B-Operating_System
(	O
Away3D	B-Application
)	O
,	O
Haxe	B-Language
(	O
Heaps.io,	O
Kha	O
)	O
and	O
JavaScript	B-Language
(	O
Babylon.js	B-Language
,	O
Three.js	B-Language
)	O
using	B-Language
WebGL	B-Library
.	O
</s>
<s>
Several	O
engines	O
exist	O
with	O
rendering	O
in	O
low-level	B-Language
C	B-Language
or	O
C++	B-Language
with	O
higher	O
level	O
scripting	O
,	O
such	O
as	O
Panda3D	B-Language
and	O
Ursina	O
for	O
Python	B-Language
,	O
Basic4GL	B-Language
,	O
and	O
Maratis	O
,	O
Polycode	O
,	O
and	O
Cafu	B-Language
for	O
Lua	B-Language
,	O
or	O
offering	O
a	O
variety	O
of	O
language	O
binding	O
options	O
such	O
as	O
,	O
HARFANG3D	O
,	O
OGRE	B-Application
and	O
the	O
Irrlicht	B-Language
Engine	I-Language
.	O
</s>
<s>
The	O
games	O
Yo	B-Application
Frankie	I-Application
!	I-Application
</s>
<s>
and	O
Sintel	B-Application
The	I-Application
Game	I-Application
were	O
developed	O
by	O
the	B-License
Blender	I-License
Foundation	I-License
to	O
showcase	O
the	O
abilities	O
of	O
the	O
Blender	B-Application
modelling	O
tool	O
and	O
the	O
erstwhile	O
Blender	B-Application
Game	I-Application
Engine	I-Application
.	O
</s>
<s>
id	O
Software	O
,	O
an	O
early	O
entrant	O
into	O
commercial	O
Linux	B-Application
gaming	I-Application
,	O
would	O
also	O
prove	O
to	O
be	O
an	O
early	O
supporter	O
of	O
free	O
gaming	O
when	O
John	O
Carmack	O
released	O
the	O
source	O
code	O
for	O
Wolfenstein	B-Application
3D	I-Application
in	O
1995	O
and	O
Doom	B-Application
in	O
1997	O
,	O
first	O
under	O
a	O
custom	O
license	O
and	O
then	O
later	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
in	O
1999	O
(	O
later	O
termed	O
id	B-Application
Tech	I-Application
1	I-Application
)	O
.	O
</s>
<s>
This	O
was	O
followed	O
by	O
the	O
release	O
of	O
Quake	B-Application
engine	I-Application
in	O
1999	O
,	O
the	O
Quake	B-Application
II	I-Application
engine	I-Application
in	O
2001	O
(	O
both	O
known	O
as	O
id	B-Application
Tech	I-Application
2	I-Application
)	O
,	O
id	B-Application
Tech	I-Application
3	I-Application
in	O
2004	O
and	O
most	O
recently	O
id	B-Application
Tech	I-Application
4	I-Application
in	O
2011	O
(	O
including	O
the	O
updated	O
version	O
from	O
the	O
Doom	B-Application
3	I-Application
:	I-Application
BFG	I-Application
Edition	I-Application
in	O
2012	O
)	O
before	O
Carmack	O
left	O
id	O
in	O
2013	O
.	O
</s>
<s>
id	B-Application
Tech	I-Application
4	I-Application
was	O
released	O
as	O
free	B-Application
software	I-Application
,	O
even	O
amongst	O
patent	O
concerns	O
from	O
Creative	O
Labs	O
over	O
Carmack	O
's	O
reverse	O
,	O
while	O
the	O
original	O
Doom	B-Application
source	O
release	O
shipped	O
without	O
music	O
due	O
to	O
complications	O
with	O
the	O
Cygnus	O
Studios	O
developed	O
DMX	O
library	O
(	O
which	O
lead	O
to	O
the	O
Linux	B-Application
version	O
being	O
selected	O
for	O
release	O
)	O
.	O
</s>
<s>
Tim	O
Sweeney	O
has	O
implied	O
this	O
issue	O
has	O
hindered	O
potential	O
releases	O
of	O
older	O
Unreal	B-Operating_System
Engine	I-Operating_System
source	O
code	O
.	O
</s>
<s>
The	O
Godot	B-Application
,	O
Nebula	O
Device	O
,	O
Plasma	B-Application
,	O
Torque	B-Application
,	O
Stride	B-Operating_System
,	O
PlayCanvas	B-Operating_System
,	O
and	O
Defold	O
engines	O
were	O
also	O
initially	O
commercial	O
and	O
proprietary	B-Application
,	O
while	O
the	O
Open	B-Application
3D	I-Application
Engine	I-Application
is	O
derived	O
from	O
released	O
code	O
from	O
Amazon	B-Application
Lumberyard	I-Application
.	O
</s>
<s>
This	O
led	O
not	O
only	O
to	O
source	O
ports	O
that	O
allowed	O
the	O
playing	O
of	O
the	O
non-free	O
games	O
based	O
on	O
these	O
engines	O
(	O
plus	O
fan	O
added	O
enhancements	O
)	O
on	O
free	O
engines	O
and	O
systems	O
,	O
but	O
has	O
also	O
to	O
the	O
production	O
of	O
standalone	O
free	B-Application
games	I-Application
.	O
</s>
<s>
These	O
include	O
Freedoom	O
,	O
Blasphemer	O
,	O
Open	O
Quartz	O
,	O
LibreQuake	O
,	O
Nexuiz/Xonotic	O
,	O
Tremulous/Unvanquished	O
,	O
Quetoo	O
,	O
and	O
OpenArena	B-Application
on	O
id	B-Application
Tech	I-Application
,	O
plus	O
Terminal	O
Overload	O
and	O
Uebergame	O
on	O
Torque	B-Application
.	O
</s>
<s>
Freeware	B-Application
games	I-Application
,	O
such	O
as	O
Harmony	O
,	O
The	O
Adventures	O
of	O
Square	O
,	O
Alien	B-Application
Arena	I-Application
,	O
World	B-Application
of	I-Application
Padman	I-Application
,	O
and	O
Urban	B-Application
Terror	I-Application
,	O
have	O
also	O
taken	O
advantage	O
of	O
these	O
free	O
engines	O
and	O
sometimes	O
have	O
given	O
code	O
back	O
to	O
the	O
community	O
.	O
</s>
<s>
Development	O
and	O
editing	O
tools	O
are	O
also	O
commonly	O
released	O
freely	O
,	O
such	O
as	O
GtkRadiant	B-Application
,	O
Qoole	B-Application
,	O
Doom	B-Application
Builder	I-Application
,	O
LibreSprite	O
,	O
LDtk	O
,	O
Tile	B-Application
Studio	I-Application
,	O
and	O
Tiled	O
.	O
</s>
<s>
Released	O
engines	O
have	O
also	O
been	O
used	O
for	O
fangames	B-Application
such	O
as	O
Sonic	B-Application
Robo	I-Application
Blast	I-Application
2	I-Application
,	O
Wolfenstein	B-Application
:	I-Application
Blade	I-Application
of	I-Application
Agony	I-Application
,	O
and	O
ZBlood/Transfusion	B-Application
,	O
and	O
even	O
commercial	O
games	O
such	O
as	O
Wrath	B-Application
:	I-Application
Aeon	I-Application
of	I-Application
Ruin	I-Application
,	O
Steel	B-Application
Storm	I-Application
,	O
and	O
DOOMBRINGER	O
,	O
on	O
the	O
DarkPlaces	O
engine	O
,	O
as	O
well	O
as	O
Hedon	O
,	O
Selaco	O
,	O
Vomitoreum	O
,	O
and	O
Supplice	O
on	O
the	O
GZDoom	O
engine	O
and	O
also	O
titles	O
by	O
Blendo	O
Games	O
on	O
the	O
id	B-Application
Tech	I-Application
2	I-Application
and	O
id	B-Application
Tech	I-Application
4	I-Application
engines	O
.	O
</s>
<s>
The	O
games	O
Ion	B-Application
Fury	I-Application
and	O
A.W.O.L	O
are	O
built	O
on	O
the	O
source	B-License
available	I-License
Build	B-Application
engine	I-Application
,	O
and	O
Excalibur	B-Application
:	I-Application
Morgana	I-Application
's	I-Application
Revenge	I-Application
on	O
Aleph	O
One	O
.	O
</s>
<s>
Formerly	O
proprietary	B-Application
games	O
such	O
as	O
Jump	B-Application
'	I-Application
n	I-Application
Bump	I-Application
,	O
Dink	B-Application
Smallwood	I-Application
,	O
Clonk	B-Application
,	O
Seven	B-Application
Kingdoms	I-Application
,	O
AstroMenace	B-Application
,	O
Warzone	B-Application
2100	I-Application
,	O
Glitch	B-Application
,	O
Maelstrom	B-Application
,	O
Planet	O
Blupi	O
,	O
Avara	B-Application
,	O
Eat	O
the	O
Whistle	O
,	O
Blades	B-Application
of	I-Application
Exile	I-Application
,	O
Star	B-Application
Control	I-Application
2	I-Application
,	O
SimCity	B-Application
,	O
Fish	B-Application
Fillets	I-Application
,	O
HoverRace	B-Application
,	O
Duelyst	B-Application
,	O
as	O
well	O
Abuse	B-Application
and	O
the	O
unfinished	O
Golgotha	B-Application
have	O
even	O
been	O
entirely	O
released	O
freely	O
,	O
including	O
multimedia	O
assets	O
and	O
levels	O
.	O
</s>
<s>
Some	O
games	O
are	O
mostly	O
free	B-Application
software	I-Application
but	O
contain	O
proprietary	B-Application
content	O
such	O
as	O
the	O
Cube	B-Application
sequel	O
,	O
Sauerbraten	B-Application
(	O
and	O
later	O
forks	B-Application
,	O
but	O
not	O
Red	B-Application
Eclipse	I-Application
)	O
,	O
Warsow	B-Application
/	O
Warfork	B-Application
,	O
or	O
the	O
former	O
id	B-Application
Tech	I-Application
mods	O
The	B-Application
Dark	I-Application
Mod	I-Application
and	O
Smokin	B-Application
 '	I-Application
Guns	I-Application
,	O
but	O
some	O
developers	O
desire	O
and/or	O
work	O
on	O
replacing	O
these	O
with	O
free	O
content	O
.	O
</s>
<s>
Derivatives	O
of	O
released	O
code	O
have	O
even	O
been	O
used	O
for	O
commercial	O
re-releases	O
of	O
vintage	O
games	O
such	O
as	O
Wolfenstein	B-Application
3D	I-Application
Classic	I-Application
for	O
iOS	B-Application
,	O
Abuse	B-Application
Classic	I-Application
for	O
iPhone	B-Device
,	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
:	I-Application
Megaton	I-Application
Edition	I-Application
,	O
Shadow	O
Warrior	O
Classic	O
Redux	O
,	O
and	O
The	B-Application
Original	I-Application
Strife	I-Application
:	I-Application
Veteran	I-Application
Edition	I-Application
.	O
</s>
<s>
Source	O
code	O
releases	O
were	O
used	O
however	O
for	O
unauthorized	O
versions	O
of	O
Lugaru	B-Application
and	O
Abuse	B-Application
that	O
were	O
allowed	O
onto	O
the	O
App	B-Application
Store	I-Application
prior	O
to	O
takedown	O
claims	O
by	O
the	O
original	O
developers	O
.	O
</s>
<s>
Primarily	O
proprietary	B-Application
developers	O
have	O
also	O
helped	O
free	O
gaming	O
by	O
creating	O
free	O
libraries	O
.	O
</s>
<s>
Loki	O
Software	O
helped	O
create	O
and	O
maintain	O
the	O
Simple	B-Operating_System
DirectMedia	I-Operating_System
Layer	I-Operating_System
and	O
OpenAL	B-Application
libraries	O
and	O
Linux	B-Application
Game	I-Application
Publishing	O
created	O
and	O
maintained	O
the	O
free	O
network	O
layer	O
Grapple	O
.	O
</s>
<s>
Many	O
libraries/infrastructures	O
have	O
been	O
created	O
without	O
corporate	O
assistance	O
however	O
,	O
such	O
as	O
the	O
online	B-Application
game	I-Application
system	O
GGZ	O
Gaming	O
Zone	O
,	O
Gamerzilla	O
achievement	O
integration	O
,	O
GamingAnywhere	O
cloud	B-Application
streaming	I-Application
,	O
Mumble	B-Language
voice	B-Application
over	I-Application
IP	I-Application
,	O
OBS	B-Language
Studio	I-Language
for	O
screencasting	B-Protocol
,	O
and	O
the	O
Lutris	B-Language
game	O
manager	O
.	O
</s>
<s>
Physics	O
engines	O
such	O
as	O
Box2D	B-Application
,	O
Bullet	B-Application
,	O
Chipmunk	B-Application
,	O
OPAL	B-Application
,	O
Open	B-Application
Dynamics	I-Application
Engine	I-Application
,	O
Tokamak	B-Application
and	O
Newton	B-Application
Game	I-Application
Dynamics	I-Application
have	O
been	O
made	O
available	O
as	O
open	B-License
source	I-License
.	O
</s>
<s>
In	O
addition	O
,	O
various	O
game	O
creators	O
are	O
free	B-Application
software	I-Application
such	O
as	O
the	O
ZZT	B-Application
remake	O
MegaZeux	O
,	O
ZGameEditor	O
,	O
versions	O
of	O
Game	B-Application
Editor	I-Application
,	O
Adventure	B-Application
Game	I-Application
Studio	I-Application
,	O
OHRRPGCE	B-Application
,	O
Game-Maker	B-Application
,	O
the	O
engine	O
behind	O
Stencyl	B-Application
,	O
the	O
original	O
Construct	B-Operating_System
,	O
GDevelop	B-Application
and	O
Godot	B-Application
.	O
</s>
<s>
Individuals	O
and	O
teams	O
have	O
continued	O
creating	O
many	O
popular	O
free	B-Application
software	I-Application
games	I-Application
,	O
starting	O
really	O
in	O
the	O
late	O
1990s	O
to	O
the	O
present	O
day	O
.	O
</s>
<s>
Many	O
of	O
these	O
are	O
clones	O
such	O
as	O
Pingus	B-Application
,	O
Lix	O
,	O
and	O
Rabbit	O
Escape	O
(	O
Lemmings	B-Application
)	O
,	O
BomberClone	O
(	O
Atomic	B-Application
Bomberman	I-Application
)	O
,	O
Enigma	B-Application
(	O
Oxyd	B-Application
)	O
,	O
Beats	B-Application
of	I-Application
Rage	I-Application
(	O
Streets	B-Application
of	I-Application
Rage	I-Application
)	O
,	O
TetriNET	B-Application
(	O
Tetris	B-Device
)	O
,	O
GAV	O
(	O
Arcade	B-Application
Volleyball	I-Application
)	O
,	O
Ace	O
of	O
Penguins	O
(	O
Microsoft	B-Application
Solitaire	I-Application
)	O
,	O
Crack	O
Attack	O
(	O
Tetris	B-Application
Attack	I-Application
)	O
,	O
System	O
Syzygy	O
(	O
Systems	O
 '	O
Twilight	O
)	O
,	O
Numpty	O
Physics	O
(	O
Crayon	B-Application
Physics	I-Application
)	O
,	O
Pathological	O
(	O
Logical	O
)	O
,	O
PainTown	O
(	O
MUGEN	B-Application
)	O
,	O
FloboPoyo	O
(	O
Puyo	B-Application
Puyo	I-Application
)	O
,	O
Paranoid	O
,	O
LBreakOut	O
2	O
,	O
and	O
Briquolo	O
(	O
Breakout	B-Application
)	O
,	O
BurgerSpace	O
(	O
BurgerTime	B-Application
)	O
,	O
Einstein	O
Puzzle	O
(	O
Sherlock	O
)	O
,	O
UltraStar	B-Device
(	O
SingStar	B-Device
)	O
,	O
OpenClonk	B-Language
(	O
Clonk	B-Application
)	O
,	O
FreeGish	O
(	O
Gish	B-Application
)	O
,	O
Hexoshi	O
(	O
Super	B-Application
Metroid	I-Application
)	O
,	O
I	O
Have	O
No	O
Tomatoes	O
(	O
Dynablaster	B-Application
)	O
,	O
Scorched	B-Language
3D	I-Language
and	O
XScorch	O
(	O
Scorched	B-Application
Earth	I-Application
)	O
,	O
FreeVikings	O
(	O
The	B-Application
Lost	I-Application
Vikings	I-Application
)	O
,	O
Savage	O
Wheels	O
(	O
Destruction	B-Application
Derby	I-Application
)	O
,	O
Penguin	O
Command	O
(	O
Missile	B-Application
Command	I-Application
)	O
,	O
Sable	O
(	O
Space	B-Application
Harrier	I-Application
)	O
,	O
Circus	B-Application
Linux	B-Application
!	O
</s>
<s>
(	O
Circus	B-Application
Atari	I-Application
)	O
,	O
Falling	O
Time	O
(	O
Fall	O
Down	O
)	O
,	O
Toppler	O
(	O
Tower	B-Application
Toppler	I-Application
)	O
,	O
Gem	O
Drop	O
X	B-Operating_System
(	O
Gem	O
Drop	O
)	O
,	O
Fish	O
Supper	O
and	O
Froggix	O
(	O
Frogger	B-Application
)	O
,	O
OpenMortal	O
(	O
Mortal	B-Application
Kombat	I-Application
)	O
,	O
Triplane	B-Application
Turmoil	I-Application
and	O
SDL	B-Operating_System
Sopwth	O
(	O
Sopwith	B-Application
)	O
,	O
Taisei	O
Project	O
(	O
Touhou	B-Application
Project	I-Application
)	O
,	O
Crown	O
and	O
Cutlass	O
(	O
Sid	B-Application
Meier	I-Application
's	I-Application
Pirates	I-Application
!	I-Application
</s>
<s>
)	O
,	O
IceBreaker	B-Application
(	O
JezzBall	B-Application
)	O
,	O
Monsterz	O
(	O
Bejeweled	B-Device
)	O
,	O
Tux	B-Application
Football	O
and	O
YSoccer	O
(	O
Sensible	B-Application
Soccer	I-Application
)	O
,	O
iMaze	O
(	O
MIDI	B-Application
Maze	I-Application
)	O
,	O
PixBros	O
(	O
Bubble	B-Application
Bobble	I-Application
)	O
,	O
Surge	O
the	O
Rabbit	O
(	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
)	O
,	O
Dave	O
Gnukem	O
(	O
Duke	B-Application
Nukem	I-Application
)	O
,	O
Minetest	B-Application
(	O
Minecraft	B-Application
)	O
,	O
SolarWolf	O
(	O
Solar	B-Application
Fox	I-Application
)	O
,	O
Tile	B-Device
World	I-Device
(	O
Chip	B-Device
's	I-Device
Challenge	I-Device
)	O
,	O
FreeOrion	B-Application
(	O
Master	B-Application
of	I-Application
Orion	I-Application
)	O
,	O
Tuxánci	B-Application
(	O
Bulánci	B-Application
)	O
,	O
Super	B-Application
Tux	I-Application
Party	O
(	O
Mario	B-Application
Party	I-Application
)	O
,	O
Neverball	O
(	O
Super	B-Application
Monkey	I-Application
Ball	I-Application
)	O
,	O
Kraptor/RafKill	O
(	O
Raptor	B-Application
:	I-Application
Call	I-Application
of	I-Application
the	I-Application
Shadows	I-Application
)	O
,	O
Trackballs	O
(	O
Marble	B-Device
Madness	I-Device
)	O
,	O
Hurrican	O
(	O
Turrican	B-Application
)	O
,	O
OpenTyrian	O
(	O
Tyrian	B-Application
)	O
,	O
HexGL	O
(	O
Wipeout	O
)	O
,	O
Zaz	B-Language
(	O
Zuma	B-Application
)	O
,	O
Ostrich	O
Riders	O
(	O
Joust	B-Application
)	O
,	O
Endless	O
Sky	O
and	O
Naev	O
(	O
Escape	B-Operating_System
Velocity	I-Operating_System
)	O
,	O
Pioneer	B-Language
and	O
Oolite	B-Language
(	O
Elite	O
)	O
,	O
SuperTux	B-Application
,	O
Secret	B-Application
Maryo	I-Application
Chronicles	I-Application
and	O
Mari0	B-Application
(	O
Super	B-Application
Mario	I-Application
Bros	I-Application
.	I-Application
)	O
,	O
WarMUX	O
and	O
Hedgewars	O
(	O
Worms	B-Application
)	O
,	O
OpenLieroX	O
,	O
NiL	B-Language
,	O
LieroLibre	O
(	O
Liero	B-Application
)	O
as	O
well	O
as	O
Frets	B-Application
on	I-Application
Fire	I-Application
(	O
Guitar	B-Application
Hero	I-Application
)	O
,	O
and	O
StepMania	B-Language
(	O
Dance	B-Application
Dance	I-Application
Revolution	I-Application
)	O
.	O
</s>
<s>
Frozen	B-Language
Bubble	I-Language
,	O
originally	O
a	O
clone	O
of	O
Puzzle	B-Application
Bobble	I-Application
,	O
has	O
become	O
a	O
classic	O
known	O
for	O
its	O
addictive	O
gameplay	O
and	O
winner	O
of	O
many	O
Linux	B-Application
Journal	O
Reader	O
's	O
Choice	O
Awards	O
.	O
</s>
<s>
These	O
games	O
and	O
others	O
have	O
also	O
helped	O
expand	O
the	O
prevalent	O
Tux	B-Application
genre	O
which	O
started	O
with	O
titles	O
and	O
like	O
A	O
Quest	O
for	O
Herring	O
and	O
are	O
related	O
to	O
the	O
activist	O
content	O
of	O
games	O
like	O
XBill	B-Application
.	O
</s>
<s>
As	O
well	O
as	O
ground	O
up	O
clones	O
,	O
open	B-License
source	I-License
re-implementations	O
of	O
various	O
proprietary	B-Application
games	O
have	O
become	O
increasingly	B-Application
common	I-Application
,	O
which	O
utilize	O
the	O
original	O
game	O
data	O
.	O
</s>
<s>
More	O
original	O
games	O
such	O
as	O
the	O
platformers	O
0verkill	O
,	O
Abe	O
's	O
Amazing	O
Adventure	O
,	O
Adventures	O
on	O
Planet	O
Zephulor	O
,	O
Alex	O
the	O
Allegator	O
4	O
,	O
Amphetamine	O
,	O
B.A.L.L.Z.	O
,	O
Cow	O
's	O
Revenge	O
,	O
Gilbert	O
and	O
the	O
doors	O
,	O
Go	B-Application
Ollie	O
!,	O
Me	O
and	O
My	O
Shadow	O
,	O
Mr.	O
</s>
<s>
Rescue	O
,	O
Nikwi	O
,	O
Plee	O
the	O
Bear	O
,	O
Super	O
Bombinhas	O
,	O
Stringrolled	O
,	O
Teeworlds	B-Application
,	O
Which	O
Way	O
Is	O
Up	O
,	O
and	O
Worminator	O
3	O
,	O
puzzle	O
games	O
such	O
as	O
Anagramarama	O
,	O
Angry	O
,	O
Drunken	O
,	O
Dwarves	O
,	O
Balls	O
Blocks	O
and	O
Mazes	O
,	O
Battery	O
,	O
Brikx	O
,	O
Chroma	O
,	O
Dynamite	O
,	O
Hex-a-Hop	O
,	O
irrlamb	O
,	O
kiki	B-Application
the	I-Application
nano	I-Application
bot	I-Application
,	O
Marble	O
Muncher	O
,	O
Memonix	O
,	O
Raincat	O
,	O
Tetzle	O
,	O
The	B-Application
Powder	I-Application
Toy	I-Application
,	O
Wizznic	O
!,	O
and	O
Xye	O
,	O
arcade	O
games	O
such	O
as	O
Apricots	B-Application
,	O
Airstrike	O
,	O
Avoision	O
,	O
Battle	O
Tanks	O
,	O
Barrage	O
,	O
C-Dogs	B-Application
,	O
Chromium	B-Language
B.S.U.	I-Language
,	O
Emilia	O
Pinball	O
,	O
the	O
Enemy	O
Lines	O
series	O
,	O
Free	O
Tennis	O
,	O
the	O
Geki	O
series	O
,	O
Hase	O
,	O
Help	O
Hannah	O
's	O
Horse	O
,	O
Heroes	O
,	O
KETM	O
,	O
Kuklomenos	O
,	O
Librerama	O
,	O
Luola	O
,	O
M.A.R.S.	O
,	O
Meat	O
Fighter	O
-	O
The	O
Weiner	O
Warrior	O
,	O
Moag	O
,	O
OilWar	O
,	O
osu	O
!,	O
Osgg	O
,	O
Overgod	O
,	O
Powermanga	O
,	O
Ri-li	O
,	O
Super	O
Transball	O
2	O
,	O
Technoball	O
Z	O
,	O
The	O
Sheep	O
Killer	O
,	O
Variations	O
on	O
Rockdodger	O
,	O
and	O
Zorn	O
,	O
have	O
been	O
able	O
to	O
carve	O
out	O
their	O
own	O
niches	O
.	O
</s>
<s>
Most	O
prominently	O
among	O
Linux	B-Application
users	O
and	O
other	O
free	O
Unix-like	B-Operating_System
systems	I-Operating_System
such	O
as	O
BSD	B-Operating_System
,	O
Solaris	B-Application
,	O
Darwin	B-Operating_System
,	O
and	O
SerenityOS	B-Language
,	O
but	O
also	O
some	O
Macintosh	B-Device
players	O
and	O
even	O
a	O
few	O
Microsoft	B-Application
Windows	I-Application
gamers	O
.	O
</s>
<s>
As	O
well	O
,	O
open	B-Application
source	I-Application
games	I-Application
have	O
been	O
made	O
available	O
for	O
Palm	B-Operating_System
OS	I-Operating_System
,	O
Android	B-Application
,	O
and	O
iOS	B-Application
mobile	O
devices	O
.	O
</s>
<s>
Additionally	O
,	O
these	O
games	O
provide	O
options	O
for	O
a	O
variety	O
of	O
alternative	O
and	O
hobbyist	O
systems	O
,	O
including	O
CP/M	B-Application
,	O
OS/2	B-Application
,	O
BeOS	B-Application
,	O
RISC	B-Operating_System
OS	I-Operating_System
,	O
QNX	B-Operating_System
,	O
IRIX	B-Operating_System
,	O
MenuetOS	B-Device
,	O
AmigaOS	B-Application
(	O
plus	O
WarpOS	B-Device
)	O
,	O
and	O
MorphOS	B-Operating_System
,	O
as	O
well	O
as	O
later	O
implementations	O
such	O
as	O
FreeDOS	B-Application
,	O
ArcaOS	B-Device
,	O
ReactOS	B-Application
,	O
Haiku	B-Language
,	O
KolibriOS	B-Operating_System
,	O
Syllable	B-Application
Desktop	I-Application
,	O
AmigaOS	B-Application
4	I-Application
,	O
and	O
AROS	B-Application
.	O
</s>
<s>
Particularly	O
prolific	O
is	O
New	O
Breed	O
Software	O
,	O
which	O
offers	O
games	O
for	O
all	O
or	O
most	O
of	O
those	O
systems	O
,	O
as	O
well	O
as	O
for	O
vintage	O
computers	O
such	O
as	O
the	O
Atari	B-Device
8-bit	I-Device
,	O
Atari	B-Device
ST	I-Device
,	O
and	O
Amiga	B-Device
,	O
homebrew	B-Application
for	O
several	O
game	O
consoles	O
such	O
as	O
the	O
Sega	B-Operating_System
Dreamcast	I-Operating_System
,	O
Sony	B-Device
PlayStation	I-Device
2	I-Device
and	O
Nintendo	B-Operating_System
Wii	I-Operating_System
,	O
handhelds	O
such	O
as	O
the	O
Sony	B-Operating_System
PSP	I-Operating_System
,	O
Nintendo	B-Device
DS	I-Device
and	O
GP2X	B-Device
,	O
as	O
well	O
as	O
mobile	O
platforms	O
such	O
as	O
OpenZaurus	B-Language
,	O
Maemo	B-Operating_System
,	O
and	O
SymbianOS	B-Operating_System
.	O
</s>
<s>
Strategy	O
and	O
simulation	O
games	O
have	O
been	O
a	O
prevalent	O
force	O
in	O
free	B-Application
software	I-Application
gaming	O
,	O
partly	O
due	O
to	O
the	O
lack	O
of	O
proprietary	B-Application
options	O
for	O
free	B-Application
software	I-Application
operating	O
systems	O
as	O
compared	O
to	O
other	O
genres	O
like	O
first-person	O
shooters	O
and	O
role-playing	O
games	O
.	O
</s>
<s>
Xconq	B-Application
and	O
XBattle	O
,	O
and	O
later	O
Freeciv	B-Application
and	O
Lincity	B-Application
,	O
began	O
the	O
trend	O
,	O
and	O
were	O
followed	O
by	O
other	O
clone	O
titles	O
like	O
FreeCol	B-Language
,	O
UnCiv	O
,	O
Crimson	B-Application
Fields	I-Application
,	O
C-evo	B-Application
,	O
LordsAWar	O
!,	O
Freelords	O
,	O
Civil	O
,	O
LGeneral	B-Application
,	O
Open	O
General	O
,	O
OpenPanzer	O
,	O
OpenCity	B-Application
,	O
OpenRTS	O
,	O
TripleA	B-Language
,	O
Mars	O
,	O
Land	O
of	O
No	O
Mercy	O
,	O
Ophiuchus	O
,	O
Mindustry	O
,	O
Tanks	O
of	O
Freedom	O
,	O
OpenRA	B-Application
,	O
OpenRCT2	B-Language
,	O
OpenTTD	B-Application
,	O
Simutrans	B-Application
,	O
StormWar	O
,	O
Advanced	B-Application
Strategic	I-Application
Command	I-Application
,	O
Tenes	B-Application
Empanadas	I-Application
Graciela	I-Application
,	O
Endgame	B-Operating_System
:	I-Operating_System
Singularity	I-Operating_System
,	O
Thousand	B-Application
Parsec	I-Application
,	O
Unknown	B-Application
Horizons	I-Application
and	O
Widelands	B-Language
.	O
</s>
<s>
The	O
Stratagus	B-Application
project	O
began	O
as	O
an	O
attempt	O
to	O
recreate	O
the	O
proprietary	B-Application
Warcraft	B-Application
II	I-Application
engine	O
,	O
under	O
the	O
name	O
FreeCraft	B-Application
.	O
</s>
<s>
Blizzard	O
Entertainment	O
sent	O
a	O
cease	O
and	O
desist	O
letter	O
in	O
2003	O
over	O
the	O
use	O
of	O
the	O
name	O
"	O
craft	O
"	O
in	O
comparison	O
to	O
Warcraft	B-Application
and	O
StarCraft	B-Application
.	O
</s>
<s>
Though	O
the	O
earlier	O
free	B-Application
software	I-Application
strategy	O
game	O
CRAFT	O
:	O
The	O
Vicious	O
Vikings	O
shared	O
the	O
name	O
"	O
craft	O
"	O
without	O
controversy	O
.	O
</s>
<s>
With	O
the	O
new	O
,	O
legally	O
inoffensive	O
name	O
Stratagus	B-Application
and	O
the	O
old	O
FreeCraft	B-Application
assets	O
renamed	O
Aleona	O
's	O
Tales	O
,	O
the	O
team	O
began	O
work	O
on	O
a	O
new	O
strategy	O
game	O
called	O
Bos	B-Language
Wars	I-Language
.	O
</s>
<s>
Development	O
on	O
this	O
game	O
still	O
continues	O
,	O
as	O
well	O
as	O
the	O
modern	O
Warcraft	B-Application
II	I-Application
port	O
Wargus	B-Application
.	O
</s>
<s>
Other	O
games	O
branched	O
out	O
of	O
the	O
engine	O
project	O
as	O
well	O
such	O
as	O
the	O
Battle	O
for	O
Mandicor	O
and	O
Astroseries	O
projects	O
,	O
the	O
StarCraft	B-Application
port	O
attempt	O
Stargus	O
,	O
and	O
most	O
recently	O
Wyrmsun	O
.	O
</s>
<s>
After	O
the	O
Stratagus	B-Application
example	O
,	O
other	O
real-time	O
strategy	O
games	O
were	O
developed	O
,	O
such	O
as	O
Globulation	B-Application
2	I-Application
,	O
which	O
experiments	O
with	O
game	O
management	O
mechanics	O
,	O
the	O
similarly	O
experimental	O
Liquid	B-Application
War	I-Application
,	O
the	O
claymation	O
based	O
Dark	O
Oberon	O
,	O
and	O
the	O
3D	O
projects	O
0	B-Application
A.D.	I-Application
(	O
a	O
former	O
freeware	B-License
project	O
)	O
,	O
Boson	O
,	O
Battles	O
of	O
Antargis	O
,	O
Spring	B-Application
and	O
Glest	B-Language
.	O
</s>
<s>
Racing	O
games	O
,	O
another	O
uncommon	O
Linux	B-Application
commercial	O
genre	O
,	O
have	O
also	O
seen	O
development	O
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
was	O
RARS	B-Application
,	O
which	O
evolved	O
following	O
the	O
principle	O
of	O
forking	B-Application
into	O
TORCS	B-Application
and	O
then	O
Speed	B-Application
Dreams	I-Application
.	O
</s>
<s>
MicroRacers	O
and	O
Toy	O
Cars	O
are	O
inspired	O
by	O
Micro	O
Machines	O
,	O
while	O
Ultimate	O
Stunts	B-Application
and	O
Stunt	O
Rally	O
,	O
are	O
rooted	O
in	O
Stunts	B-Application
.	O
</s>
<s>
Other	O
racing	O
games	O
include	O
versions	O
of	O
Racer	B-Application
,	O
VDrift	B-Application
,	O
Rigs	B-Language
of	I-Language
Rods	I-Language
,	O
Slune	O
,	O
GLtron	B-Application
and	O
Armagetron	B-Application
Advanced	I-Application
,	O
YORG	O
,	O
the	O
Mario	B-Application
Kart	I-Application
–	O
inspired	O
SuperTuxKart	B-Application
,	O
Elasto	B-Application
Mania	I-Application
clone	O
X-Moto	B-Language
,	O
SkyRoads	B-Application
imitator	O
Orbit-Hopper	O
,	O
sledding	O
game	O
Extreme	O
Tux	B-Application
Racer	I-Application
,	O
the	O
text	O
based	O
ZRacer	O
,	O
and	O
the	O
top-down	O
Trophy	O
,	O
Dust	B-Language
Racing	I-Language
2D	I-Language
and	O
Pixel	O
Wheels	O
.	O
</s>
<s>
WorldForge	B-Protocol
,	O
Ryzom	B-Protocol
,	O
Crossfire	B-Protocol
,	O
Solipsis	B-Protocol
,	O
Illarion	O
,	O
and	O
The	O
Mana	O
World	O
are	O
further	O
examples	O
of	O
increasing	O
diversification	O
,	O
offering	O
free	O
massively	B-Protocol
multiplayer	I-Protocol
online	I-Protocol
role-playing	I-Protocol
game	I-Protocol
worlds	O
.	O
</s>
<s>
Single-player	O
role-playing	O
games	O
are	O
also	O
available	O
,	O
such	O
as	O
A	B-Application
Dark	I-Application
Room	I-Application
,	O
Heroes	O
of	O
Allacrost	O
,	O
Valyria	O
Tear	O
,	O
Empty	O
Clip	O
,	O
Summoning	O
Wars	O
,	O
GNU	O
FreeDink	O
,	O
FLARE	O
,	O
Heroine	O
Dusk	O
,	O
FreedroidRPG	O
,	O
the	O
Cube	B-Application
World	I-Application
inspired	O
Veloren	O
,	O
and	O
the	O
Pokémon	O
derived	O
Tuxemon	O
,	O
OPMon	O
,	O
and	O
Pigeon	O
Ascent	O
.	O
</s>
<s>
The	O
rise	O
of	O
the	O
independent	O
game	O
development	O
in	O
the	O
2000s	O
and	O
2010s	O
was	O
partly	O
driven	O
by	O
the	O
growing	O
ecosystem	O
of	O
open-source	B-License
libraries	O
and	O
engines	O
;	O
indie	O
developers	O
utilized	O
the	O
open-source	B-License
ecosystem	O
due	O
to	O
good	O
cross-platform	B-Operating_System
capabilities	O
and	O
availability	O
for	O
limited	O
financial	O
burden	O
.	O
</s>
<s>
Game	O
jams	O
such	O
as	O
Ludum	O
Dare	O
and	O
Game	O
Off	O
are	O
often	O
run	O
on	O
open	B-License
source	I-License
principles	I-License
,	O
frequently	O
using	B-Language
free	O
frameworks	O
such	O
as	O
pygame	B-Operating_System
,	O
Arcade	O
,	O
Ruby2D	O
,	O
Gosu	O
,	O
SuperPower	O
,	O
Ebitengine	O
,	O
nCine	O
,	O
Wasabi2D	O
,	O
Panda	O
,	O
Solarus	O
,	O
GGEZ	O
,	O
Starling	B-Language
,	O
MonoGame	B-Language
,	O
LibGDX	B-Library
,	O
Twine	B-Application
,	O
Phaser	B-Application
,	O
Cocos2d	B-Application
,	O
Solar2D	B-Operating_System
,	O
Ren'Py	B-Language
and	O
LÖVE	O
.	O
</s>
<s>
Educational	O
languages	O
such	O
as	O
Snap	B-Application
!	I-Application
</s>
<s>
and	O
Scratch	B-Language
are	O
also	O
free	B-Application
software	I-Application
.	O
</s>
<s>
Individual	O
developers	O
such	O
as	O
Jason	O
Rohrer	O
,	O
creator	O
of	O
Passage	B-Application
and	O
One	B-Application
Hour	I-Application
One	I-Application
Life	I-Application
,	O
and	O
Kenta	B-Application
Cho	I-Application
have	O
embraced	O
open	B-License
source	I-License
.	O
</s>
<s>
Despite	O
its	O
initial	O
roots	O
as	O
small	O
private	O
projects	O
,	O
the	O
free	B-Application
software	I-Application
gaming	O
scene	O
has	O
been	O
becoming	O
progressively	O
more	O
organized	O
.	O
</s>
<s>
The	O
roots	O
of	O
this	O
even	O
go	B-Application
back	O
as	O
far	O
as	O
the	O
games	O
created	O
for	O
the	B-Application
GNU	I-Application
Project	I-Application
and	O
to	O
the	O
original	O
larger-scale	O
free	B-Application
software	I-Application
projects	O
like	O
Freeciv	B-Application
.	O
</s>
<s>
Still	O
,	O
for	O
the	O
most	O
part	O
free	B-Application
game	I-Application
development	O
had	O
very	O
little	O
organization	O
throughout	O
its	O
history	O
.	O
</s>
<s>
Popular	O
games	O
were	O
generally	O
separate	O
efforts	O
,	O
except	O
for	O
instances	O
of	O
people	O
working	O
on	O
them	O
known	O
for	O
other	O
projects	O
such	O
as	O
Ingo	O
Ruhnke	O
(	O
Pingus	B-Application
)	O
,	O
Bill	B-Language
Kendrick	I-Language
(	O
SuperTux	B-Application
)	O
and	O
Steve	O
Baker	O
(	O
TuxKart	B-Application
)	O
.	O
</s>
<s>
Games	O
were	O
commonly	O
found	O
in	O
directories	O
such	O
as	O
The	O
Linux	B-Application
Game	I-Application
Tome	B-Language
and	O
Freshmeat	O
and	O
hosted	O
on	O
sites	O
like	O
SourceForge	B-Application
and	O
GNU	B-Protocol
Savannah	I-Protocol
,	O
but	O
they	O
were	O
largely	O
only	O
ever	O
brought	O
together	O
in	O
the	O
form	O
of	O
disorganized	O
lists	O
.	O
</s>
<s>
The	O
launch	O
of	O
the	O
GNOME	B-Application
and	O
KDE	B-Application
desktop	O
projects	O
in	O
the	O
late	O
1990s	O
organized	O
application	O
and	O
,	O
to	O
a	O
certain	O
extent	O
,	O
game	O
development	O
.	O
</s>
<s>
Both	O
attempts	O
to	O
create	O
a	O
more	O
usable	O
Linux	B-Application
desktop	O
attracted	O
volunteers	O
to	O
make	O
utilities	O
to	O
that	O
end	O
.	O
</s>
<s>
These	O
programs	O
included	O
games	O
,	O
mostly	O
recreations	O
of	O
small	O
games	O
like	O
Minesweeper	B-Application
or	O
Solitaire	B-Algorithm
that	O
come	O
with	O
Microsoft	B-Application
Windows	I-Application
,	O
arcade	O
classics	O
and	O
the	O
like	O
,	O
games	O
from	O
combined	O
sets	O
such	O
as	O
Microsoft	B-Application
Entertainment	I-Application
Pack	I-Application
,	O
and	O
occasionally	O
original	O
ideas	O
.	O
</s>
<s>
The	O
variety	O
and	O
amount	O
of	O
these	O
games	O
,	O
and	O
other	O
free	B-Application
games	I-Application
easily	O
found	O
in	O
software	O
repositories	O
,	O
have	O
had	O
GNOME	B-Application
or	O
KDE-enabled	O
Linux	B-Application
called	O
a	O
better	O
option	O
for	O
out	B-General_Concept
of	I-General_Concept
the	I-General_Concept
box	I-General_Concept
casual	O
gaming	O
than	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
Many	O
such	O
games	O
are	O
packaged	O
into	O
kdegames	O
and	O
the	O
erstwhile	O
GNOME	B-Application
Games	O
package	O
.	O
</s>
<s>
Examples	O
include	O
GNOME	B-Algorithm
Aisleriot	I-Algorithm
,	O
GNOME	B-Device
Quadrapassel	I-Device
,	O
GNOME	B-Application
Tetravex	O
,	O
GNOME	B-Application
Mines	I-Application
,	O
GNOME	B-Device
Robots	I-Device
,	O
GNOME	B-Application
Nibbles	I-Application
,	O
and	O
KTuberling	O
,	O
KMahjongg	B-Application
,	O
KGoldrunner	B-Application
,	O
KBreakout	B-Application
,	O
KsirK	O
,	O
plus	O
the	O
original	O
game	O
Konquest	O
.	O
</s>
<s>
Although	O
designed	O
primarily	O
for	O
application	O
development	O
,	O
the	O
underlying	O
GTK	B-Application
and	O
Qt	B-Language
toolkits	I-Language
have	O
also	O
been	O
used	O
broadly	O
for	O
game	O
development	O
,	O
as	O
have	O
wxWidgets	B-Language
,	O
Tk	B-Application
and	O
FLTK	B-Language
.	O
</s>
<s>
The	O
availability	O
of	O
free	B-Application
game	I-Application
engines	O
,	O
such	O
as	O
Stratagus	B-Application
,	O
Pygame	B-Operating_System
,	O
Sauerbraten	B-Application
and	O
ioquake3	B-Application
have	O
also	O
helped	O
unify	O
free	B-Application
software	I-Application
development	I-Application
by	O
making	O
the	O
engine	O
projects	O
themselves	O
hubs	O
of	O
activity	O
for	O
games	O
that	O
make	O
use	O
of	O
them	O
.	O
</s>
<s>
The	B-Application
Battle	I-Application
for	I-Application
Wesnoth	I-Application
project	O
was	O
started	O
in	O
2003	O
and	O
quickly	O
became	O
popular	O
to	O
both	O
players	O
and	O
editors	O
.	O
</s>
<s>
It	O
also	O
showcased	O
some	O
new	O
ideas	O
when	O
it	O
came	O
to	O
free	B-Application
game	I-Application
development	O
.	O
</s>
<s>
Like	O
Freeciv	B-Application
before	O
it	O
,	O
it	O
utilized	O
the	O
efforts	O
of	O
the	O
gaming	O
and	O
free	B-Application
software	I-Application
community	O
and	O
their	O
code	O
,	O
levels	O
and	O
artwork	O
contributions	O
but	O
it	O
also	O
accepted	O
storyline	O
contributions	O
and	O
ideas	O
for	O
the	O
game	O
's	O
entire	O
fictional	O
universe	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
project	O
is	O
worked	O
on	O
by	O
many	O
well-known	O
free	O
programmers	O
,	O
artists	O
,	O
designers	O
and	O
musicians	O
such	O
as	O
the	O
co-founder	O
of	O
the	O
Open	B-License
Source	I-License
Initiative	O
Eric	O
S	O
.	O
Raymond	O
,	O
and	O
Linux	B-Operating_System
kernel	I-Operating_System
hacker	O
Rusty	O
Russell.Vega	O
Strike	O
has	O
similarly	O
allowed	O
its	O
community	O
to	O
expand	O
the	O
game	O
and	O
the	O
surrounding	O
lore	O
while	O
maintaining	O
canon	O
consistency	O
.	O
</s>
<s>
The	O
Wesnoth	B-Application
developers	O
also	O
worked	O
on	O
Frogatto	B-Application
&	I-Application
Friends	I-Application
,	O
which	O
features	O
a	O
free	O
engine	O
but	O
mostly	O
proprietary	B-Application
game	O
data	O
.	O
</s>
<s>
The	O
general	O
lack	O
of	O
unity	O
and	O
organization	O
has	O
created	O
and	O
continues	O
to	O
generate	O
some	O
controversy	O
among	O
the	O
free	B-Application
software	I-Application
community	O
,	O
with	O
problems	O
of	O
"	O
reinventing	O
the	O
wheel	O
"	O
by	O
making	O
similar	O
clones	O
,	O
games	O
and	O
multimedia	O
resources	O
being	O
cited	O
as	O
a	O
notable	O
problem	O
to	O
free	B-Application
game	I-Application
development	O
.	O
</s>
<s>
Traditionally	O
free	B-Application
software	I-Application
video	O
games	O
were	O
developed	O
as	O
individual	O
projects	O
,	O
some	O
small	O
scale	O
and	O
others	O
larger	O
scale	O
.	O
</s>
<s>
More	O
recently	O
free	B-Application
software	I-Application
development	I-Application
teams	O
have	O
started	O
appearing	O
,	O
groups	O
that	O
function	O
like	O
software	B-Application
companies	I-Application
and	O
create	O
multiple	O
pieces	O
of	O
work	O
.	O
</s>
<s>
Examples	O
include	O
the	O
developer	O
Parallel	O
Realities	O
,	O
which	O
have	O
released	O
the	O
games	O
Project	B-Application
:	I-Application
Starfighter	I-Application
,	O
The	O
Legend	O
of	O
Edgar	O
,	O
Blob	O
Wars	O
:	O
Metal	O
Blob	O
Solid	O
,	O
as	O
well	O
as	O
its	O
sequel	O
,	O
Blob	O
Wars	O
:	O
Blob	O
and	O
Conquer	O
.	O
</s>
<s>
The	O
Linux	B-Application
Game	I-Application
Tome	B-Language
"	O
Game	O
of	O
the	O
Month	O
"	O
team	O
was	O
an	O
open	O
group	O
of	O
game	O
developers	O
that	O
revamp	O
old	O
free	B-Application
software	I-Application
games	I-Application
.	O
</s>
<s>
Some	O
examples	O
include	O
the	O
transformation	O
of	O
TuxKart	B-Application
into	O
the	O
more	O
modern	O
SuperTuxKart	B-Application
,	O
work	O
on	O
Pingus	B-Application
and	O
SuperTux	B-Application
,	O
and	O
Lincity-NG	B-Application
,	O
an	O
updated	O
version	O
of	O
Lincity	B-Application
with	O
superior	O
graphics	O
.	O
</s>
<s>
A	O
more	O
recent	O
project	O
with	O
similar	O
goals	O
exists	O
called	O
LibreGames	O
,	O
which	O
has	O
worked	O
on	O
Jump	B-Application
'	I-Application
n	I-Application
Bump	I-Application
,	O
OpenAlchemist	O
and	O
FreeTumble	O
and	O
JAG	O
.	O
</s>
<s>
PlayPower	B-Device
is	O
a	O
non-profit	O
organization	O
founded	O
in	O
2008	O
designed	O
to	O
create	O
free	O
educational	O
computer	O
software	O
for	O
low	O
income	O
families	O
in	O
India	O
and	O
other	O
developing	O
countries	O
.	O
</s>
<s>
The	O
Tux4Kids	O
initiative	O
also	O
maintains	O
various	O
educational	O
games	O
featuring	O
the	O
child-friendly	O
Tux	B-Application
character	O
such	O
as	O
Tux	B-Language
Paint	I-Language
,	O
Tux	B-Language
,	I-Language
of	I-Language
Math	I-Language
Command	I-Language
,	O
Tux	B-Language
Typing	I-Language
and	O
related	O
efforts	O
.	O
</s>
<s>
The	O
GCompris	B-Language
suite	O
is	O
also	O
available	O
from	O
KDE	B-Application
,	O
and	O
the	O
activity	O
centre	O
Childsplay	O
is	O
also	O
available	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
content	O
repositories	O
such	O
as	O
OpenGameArt.org,	O
Wikimedia	O
Commons	O
,	O
Openclipart	O
,	O
and	O
The	O
Freesound	O
Project	O
have	O
enabled	O
developers	O
to	O
easily	O
find	O
appropriately-licensed	O
content	O
rather	O
than	O
relying	O
on	O
programmer	B-General_Concept
art	I-General_Concept
.	O
</s>
<s>
Such	O
content	O
is	O
often	O
under	O
Creative	O
Commons	O
licenses	O
or	O
those	O
in	O
the	O
GNU	B-License
GPL	I-License
family	O
,	O
easily	O
facilitating	O
use	O
by	O
most	O
free	B-Application
software	I-Application
projects	O
.	O
</s>
<s>
GitHub	B-Application
,	O
GitLab	B-Application
and	O
Gitea	B-Application
now	O
hosts	O
a	O
significant	O
amount	O
of	O
free	B-License
and	I-License
open-source	I-License
games	O
.	O
</s>
<s>
The	O
itch.io	O
service	O
is	O
also	O
a	O
host	O
for	O
many	O
open	B-Application
source	I-Application
games	I-Application
,	O
and	O
also	O
features	O
an	O
open	B-License
source	I-License
client	O
.	O
</s>
<s>
The	O
same	O
is	O
true	O
for	O
competitor	O
Game	O
Jolt	O
,	O
and	O
was	O
also	O
the	O
case	O
for	O
former	O
distributor	O
Desura	B-Language
.	O
</s>
<s>
A	O
number	O
of	O
open	B-Application
source	I-Application
games	I-Application
have	O
even	O
been	O
made	O
available	O
on	O
Steam	B-Application
.	O
</s>
<s>
Many	O
free	B-Application
software	I-Application
games	I-Application
are	O
also	O
available	O
from	O
Flathub	B-Language
and	O
Snap	B-Application
.	O
</s>
