<s>
Underrail	B-Application
is	O
a	O
2015	O
role-playing	O
video	O
game	O
by	O
Stygian	O
Software	O
for	O
Windows	O
.	O
</s>
<s>
An	O
expansion	O
pack	O
,	O
Underrail	B-Application
:	I-Application
Expedition	I-Application
,	O
was	O
released	O
in	O
2019	O
while	O
a	O
sequel	O
,	O
Underrail	B-Application
:	O
Infusion	O
,	O
is	O
under	O
development	O
.	O
</s>
<s>
Underrail	B-Application
is	O
a	O
post-apocalyptic	O
role-playing	O
game	O
focused	O
on	O
combat	O
and	O
exploration	O
.	O
</s>
<s>
The	O
game	O
's	O
ruleset	O
is	O
mainly	O
inspired	O
by	O
the	O
SPECIAL	O
system	O
from	O
the	O
Fallout	B-Application
series	I-Application
.	O
</s>
<s>
The	O
turn-based	O
combat	O
system	O
is	O
similar	O
to	O
Fallout	B-Application
's	O
with	O
more	O
options	O
added	O
on	O
top	O
of	O
it	O
,	O
such	O
as	O
the	O
use	O
of	O
special	O
abilities	O
,	O
psionics	O
and	O
more	O
combat	O
utilities	O
.	O
</s>
<s>
The	O
game	O
is	O
set	O
in	O
the	O
far	O
future	O
when	O
the	O
Earth	O
's	O
surface	O
has	O
been	O
uninhabitable	O
for	O
a	O
long	O
time	O
and	O
the	O
remaining	O
humans	O
live	O
in	O
the	O
eponymous	O
Underrail	B-Application
metro	O
network	O
,	O
where	O
conflicting	O
factions	O
struggle	O
violently	O
to	O
survive	O
in	O
the	O
harsh	O
underground	O
conditions	O
.	O
</s>
<s>
The	O
scarcest	O
resources	O
in	O
Underrail	B-Application
are	O
food	O
and	O
living	O
space	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
greater	O
background	O
plot	O
concerning	O
the	O
nature	O
of	O
time	O
,	O
but	O
the	O
game	O
is	O
mostly	O
about	O
the	O
inhabitants	O
of	O
Underrail	B-Application
,	O
their	O
politics	O
,	O
strife	O
and	O
the	O
dangers	O
of	O
Underrail	B-Application
itself	O
.	O
</s>
<s>
The	O
player	O
takes	O
on	O
the	O
role	O
of	O
a	O
new	O
member	O
of	O
one	O
of	O
the	O
stations	O
on	O
the	O
fringe	O
of	O
Underrail	B-Application
.	O
</s>
<s>
The	O
story	O
is	O
narrated	O
primarily	O
through	O
dialogue	O
with	O
non-player	O
characters	O
inhabiting	O
the	O
world	O
of	O
Underrail	B-Application
.	O
</s>
<s>
Game	O
engine	O
development	O
for	O
Underrail	B-Application
began	O
in	O
late	O
2008	O
.	O
</s>
<s>
The	O
game	O
's	O
custom	O
engine	O
and	O
development	O
tools	O
are	O
built	O
using	O
C#	B-Application
,	O
Microsoft	O
's	O
.NET	B-Application
4.0	I-Application
framework	O
and	O
XNA	O
Game	O
Studio	O
4.0	O
.	O
</s>
<s>
Since	O
its	O
initial	O
demo	O
version	O
release	O
in	O
2012	O
,	O
updated	O
versions	O
of	O
Underrail	B-Application
were	O
released	O
roughly	O
every	O
three	O
or	O
four	O
months	O
.	O
</s>
<s>
The	O
first	O
trailer	O
for	O
Underrail	B-Application
was	O
released	O
on	O
March	O
11	O
,	O
2013	O
,	O
showcasing	O
alpha	O
version	O
gameplay	O
footage	O
.	O
</s>
<s>
On	O
August	O
22	O
,	O
2012	O
,	O
a	O
demo	O
of	O
Underrail	B-Application
was	O
released	O
on	O
IndieDB	O
.	O
</s>
<s>
On	O
December	O
6	O
,	O
2012	O
,	O
an	O
alpha	O
version	O
became	O
available	O
on	O
both	O
Desura	B-Language
and	O
GamersGate	O
digital	O
distribution	O
platforms	O
,	O
and	O
on	O
September	O
24	O
,	O
2013	O
,	O
alpha	O
version	O
became	O
available	O
as	O
early	O
access	O
on	O
the	O
Steam	B-Application
store	I-Application
as	O
well	O
.	O
</s>
<s>
An	O
expansion	O
,	O
Underrail	B-Application
:	I-Application
Expedition	I-Application
,	O
was	O
released	O
on	O
July	O
22	O
,	O
2019	O
,	O
and	O
features	O
a	O
new	O
plotline	O
based	O
in	O
new	O
locations	O
,	O
alongside	O
other	O
gameplay	O
changes	O
and	O
additions	O
.	O
</s>
<s>
A	O
sequel	O
,	O
Underrail	B-Application
:	O
Infusion	O
,	O
is	O
under	O
development	O
.	O
</s>
