<s>
UFO	B-Application
:	I-Application
Alien	I-Application
Invasion	I-Application
is	O
a	O
strategy	B-Application
video	I-Application
game	I-Application
in	O
which	O
the	O
player	O
fights	O
aliens	O
that	O
are	O
trying	O
to	O
take	O
control	O
of	O
the	O
Earth	O
.	O
</s>
<s>
The	O
game	O
is	O
heavily	O
influenced	O
by	O
the	O
X-COM	B-Application
series	O
,	O
especially	O
X-COM	B-Application
:	I-Application
UFO	I-Application
Defense	I-Application
.	O
</s>
<s>
It	O
is	O
based	O
on	O
a	O
modified	O
id	B-Application
Tech	I-Application
2	I-Application
engine	O
,	O
and	O
runs	O
on	O
Linux	B-Application
,	O
FreeBSD	B-Operating_System
,	O
OpenBSD	B-Operating_System
,	O
Microsoft	B-Application
Windows	I-Application
,	O
AmigaOS	B-Application
4	I-Application
,	O
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
for	O
both	O
PowerPC	O
and	O
Intel	O
Macs	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
version	O
for	O
Android	B-Application
,	O
published	O
on	O
Android	B-Application
Market	I-Application
.	O
</s>
<s>
The	O
game	O
takes	O
inspiration	O
from	O
the	O
X-COM	B-Application
series	O
by	O
Mythos	O
Games	O
and	O
MicroProse	O
.	O
</s>
<s>
However	O
,	O
it	O
is	O
neither	O
a	O
sequel	B-Language
nor	O
a	O
remake	O
of	O
any	O
X-COM	B-Application
or	O
other	O
commercial	O
title	O
:	O
"	O
What	O
we	O
as	O
a	O
team	O
wanted	O
to	O
make	O
is	O
a	O
brand	O
new	O
experience	O
that	O
tries	O
to	O
surpass	O
the	O
quality	O
of	O
games	O
from	O
1992	O
,	O
rather	O
than	O
simply	O
recreate	O
them	O
with	O
flashier	O
graphics.	O
"	O
</s>
<s>
UFO	B-Application
:	I-Application
Alien	I-Application
Invasion	I-Application
is	O
a	O
squad-based	O
tactical	O
strategy	B-Application
game	I-Application
in	O
the	O
tradition	O
of	O
the	O
classic	O
X-COM	B-Application
series	O
of	O
games	O
(	O
the	O
player	O
controls	O
a	O
secret	O
organization	O
charged	O
with	O
defending	O
Earth	O
from	O
a	O
brutal	O
alien	O
enemy	O
)	O
.	O
</s>
<s>
Like	O
the	O
original	O
X-COM	B-Application
games	O
,	O
UFO:AI	B-Application
has	O
two	O
main	O
modes	O
of	O
play	O
:	O
Geoscape	O
mode	O
and	O
Tactical	O
(	O
also	O
known	O
as	O
Battlescape	O
)	O
mode	O
.	O
</s>
<s>
Interceptor	O
aircraft	O
can	O
be	O
launched	O
to	O
shoot	O
down	O
UFOs	B-Application
and	O
dispatch	O
dropships	O
in	O
response	O
to	O
alien	O
activity	O
across	O
the	O
globe	O
.	O
</s>
<s>
Unlike	O
X-COM	B-Application
and	O
many	O
similar	O
games	O
,	O
there	O
is	O
no	O
one	O
"	O
super	O
weapon	O
"	O
that	O
the	O
player	O
rushes	O
to	O
and	O
then	O
arms	O
every	O
single	O
soldier	O
with	O
as	O
soon	O
as	O
they	O
can	O
but	O
should	O
rather	O
keep	O
a	O
healthy	O
,	O
balanced	O
arsenal	O
to	O
be	O
effective	O
at	O
different	O
ranges	O
and	O
amounts	O
of	O
cover	O
.	O
</s>
<s>
This	O
engine	O
is	O
free	B-Application
software	I-Application
,	O
licensed	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
Since	O
end	O
of	O
2012	O
UFO:AI	B-Application
'	O
s	O
artwork	O
is	O
only	O
licensed	O
under	O
various	O
open	O
source/open	O
content	O
licenses	O
(	O
mostly	O
CC	O
BY-SA	O
3.0	O
and	O
public	O
domainufoai-data_2.5-1_copyright	O
on	O
metadata.ftp-master.debian.org	O
)	O
,	O
which	O
makes	O
the	O
game	O
fully	O
free	B-License
and	I-License
open	I-License
source	I-License
software	I-License
and	O
Debian	O
's	O
DFSGufoai-data	O
on	O
packages.debian.org	O
compliant	O
,	O
which	O
allows	O
the	O
inclusion	O
into	O
Linux	B-Application
distributions	I-Application
.	O
</s>
<s>
Reception	O
UFO:AI	B-Application
was	O
nominated	O
for	O
"	O
Best	O
project	O
for	O
Gamers	O
"	O
in	O
the	O
SourceForge	B-Application
2007	O
and	O
2008	O
Community	O
Choice	O
Awards	O
.	O
</s>
<s>
In	O
2008	O
APCMag.com	O
named	O
UFO	B-Application
:	I-Application
Alien	I-Application
Invasion	I-Application
among	O
the	O
Top	O
5	O
best	O
(	O
free	O
)	O
open	O
source	O
games	O
.	O
</s>
<s>
Linux	B-Application
Game	O
News	O
named	O
it	O
the	O
Best	O
Open	O
Source	O
Game	O
in	O
the	O
Turn-Based	O
category	O
in	O
September	O
2012	O
and	O
it	O
was	O
positively	O
noted	O
by	O
Linux	B-Application
Journal	O
.	O
</s>
<s>
Between	O
2006	O
and	O
May	O
2017	O
UFO:AI	B-Application
''	O
was	O
downloaded	O
from	O
Sourceforge	B-Application
over	O
1.7	O
million	O
times	O
.	O
</s>
