<s>
Undertow	B-Application
is	O
a	O
video	O
game	O
developed	O
by	O
Chair	O
Entertainment	O
for	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
's	O
Xbox	B-Device
Live	I-Device
Arcade	I-Device
service	O
.	O
</s>
<s>
Undertow	B-Application
features	O
a	O
15	O
level	O
campaign	O
for	O
single-player	O
or	O
co-op	O
and	O
two	O
multiplayer	O
modes	O
for	O
up	O
to	O
16	O
players	O
.	O
</s>
<s>
Undertow	B-Application
is	O
set	O
underwater	O
,	O
where	O
an	O
aquatic	O
alien	O
race	O
known	O
as	O
the	O
Elect	O
launches	O
an	O
attack	O
on	O
the	O
polar	O
ice	O
caps	O
,	O
causing	O
them	O
to	O
melt	O
and	O
flood	O
the	O
planet	O
.	O
</s>
<s>
With	O
the	O
city	O
of	O
Atlantis	B-Application
thawed	O
by	O
the	O
melting	O
of	O
the	O
ice	O
caps	O
the	O
Atlanteans	B-Application
also	O
become	O
a	O
threat	O
,	O
vowing	O
to	O
reclaim	O
the	O
planet	O
and	O
rule	O
again	O
.	O
</s>
<s>
On	O
April	O
23	O
,	O
2007	O
,	O
Chair	O
Entertainment	O
announced	O
through	O
a	O
company	O
press	O
release	O
that	O
Undertow	B-Application
was	O
in	O
development	O
for	O
Xbox	B-Device
Live	I-Device
Arcade	I-Device
.	O
</s>
<s>
Chair	O
began	O
production	O
on	O
Undertow	B-Application
in	O
the	O
fall	O
of	O
2006	O
and	O
the	O
game	O
was	O
released	O
on	O
November	O
21	O
,	O
2007	O
.	O
</s>
<s>
On	O
January	O
18	O
,	O
2008	O
,	O
Microsoft	O
selected	O
Undertow	B-Application
for	O
its	O
free	O
game	O
offer	O
from	O
January	O
23	O
through	O
January	O
27	O
as	O
compensation	O
for	O
the	O
holiday	O
traffic/outage	O
experienced	O
on	O
Xbox	B-Application
Live	I-Application
.	O
</s>
<s>
A	O
single	O
downloadable	B-Protocol
content	I-Protocol
pack	O
was	O
released	O
for	O
the	O
game	O
.	O
</s>
<s>
The	O
game	O
received	O
numerous	O
Editors	O
Choice	O
Awards	O
from	O
gaming	O
publications	O
and	O
websites	O
,	O
including	O
Official	O
Xbox	B-Operating_System
Magazine	O
,	O
IGN	O
,	O
and	O
Team	O
Xbox	B-Operating_System
.	O
</s>
<s>
IGN	O
also	O
selected	O
Undertow	B-Application
as	O
its	O
Game	O
of	O
the	O
Month	O
for	O
November	O
2007	O
.	O
</s>
<s>
Undertow	B-Application
was	O
nominated	O
for	O
Microsoft	O
's	O
2007	O
XBLA	B-Device
Awards	O
and	O
1UP	O
's	O
2007	O
Editors	O
Choice	O
Awards	O
and	O
was	O
selected	O
by	O
Official	O
Xbox	B-Operating_System
Magazine	O
as	O
its	O
2007	O
Game	O
of	O
the	O
Year	O
for	O
Xbox	B-Device
Live	I-Device
Arcade	I-Device
.	O
</s>
<s>
As	O
of	O
year-end	O
2010	O
,	O
Undertow	B-Application
has	O
moved	O
more	O
than	O
634,000	O
units	O
.	O
</s>
