<s>
Under	B-Application
the	I-Application
Ice	I-Application
is	O
a	O
submarine	O
warfare	O
video	O
game	O
for	O
the	O
Atari	B-Device
ST	I-Device
and	O
IBM	B-Device
PC	I-Device
compatibles	O
running	O
GEM	B-Application
.	O
</s>
<s>
A	O
key	O
element	O
of	O
the	O
game	O
was	O
an	O
accurate	O
simulation	O
of	O
the	O
performance	O
of	O
sonar	B-Application
,	O
the	O
various	O
classes	O
of	O
submarines	O
,	O
and	O
their	O
weapons	O
.	O
</s>
<s>
Sonar	B-Application
modeling	O
is	O
an	O
important	O
aspect	O
of	O
the	O
game	O
.	O
</s>
<s>
Active	O
sonar	B-Application
is	O
also	O
supported	O
,	O
normally	O
used	O
in	O
short	O
bursts	O
to	O
quickly	O
determine	O
the	O
exact	O
location	O
of	O
a	O
target	O
.	O
</s>
