<s>
is	O
a	O
horizontally	O
scrolling	O
shooter	O
arcade	B-Application
video	I-Application
game	I-Application
developed	O
by	O
Kaneko	O
and	O
published	O
by	O
Taito	O
in	O
1988	O
.	O
</s>
<s>
It	O
was	O
ported	O
to	O
the	O
PC	B-General_Concept
Engine	I-General_Concept
by	O
Taito	O
and	O
was	O
released	O
on	O
December	O
22	O
,	O
1989	O
.	O
</s>
<s>
There	O
was	O
also	O
a	O
Mega	B-Operating_System
Drive	I-Operating_System
port	O
by	O
Toho	B-Application
entitled	O
"	O
Heavy	B-Application
Unit	I-Application
:	O
Mega	B-Operating_System
Drive	I-Operating_System
Special	O
"	O
released	O
on	O
December	O
26	O
,	O
1990	O
.	O
</s>
<s>
The	O
player	O
must	O
navigate	O
a	O
"	O
Heavy	B-Application
Unit	I-Application
"	O
,	O
a	O
heavily	O
armed	O
,	O
transforming	O
mecha	O
,	O
in	O
order	O
to	O
defeat	O
the	O
onslaught	O
and	O
protect	O
the	O
human	O
colony	O
.	O
</s>
<s>
Players	O
started	O
controlling	O
the	O
Heavy	B-Application
Unit	I-Application
in	O
its	O
space-ship	O
form	O
as	O
default	O
.	O
</s>
<s>
A	O
checkpoint	O
was	O
active	O
however	O
and	O
the	O
Heavy	B-Application
Unit	I-Application
only	O
had	O
one	O
hit	O
.	O
</s>
<s>
In	O
Japan	O
,	O
Game	O
Machine	O
listed	O
Heavy	B-Application
Unit	I-Application
on	O
their	O
January	O
1	O
,	O
1989	O
issue	O
as	O
being	O
the	O
fifth	O
most-successful	O
table	O
arcade	B-Application
unit	O
of	O
the	O
month	O
.	O
</s>
