<s>
SDI	B-Application
-	O
Strategic	O
Defense	O
Initiative	O
,	O
or	O
simply	O
titled	O
SDI	B-Application
and	O
sometimes	O
known	O
as	O
Global	B-Application
Defense	I-Application
,	O
is	O
a	O
1987	B-Application
horizontally	O
scrolling	O
shooter	O
produced	O
and	O
released	O
internationally	O
in	O
arcades	O
by	O
Sega	O
.	O
</s>
<s>
Players	O
control	O
a	O
satellite	B-Application
and	O
must	O
destroy	O
enemies	O
by	O
moving	O
a	O
crosshair	O
over	O
them	O
and	O
firing	O
the	O
satellite	B-Application
's	O
weapons	O
.	O
</s>
<s>
Players	O
control	O
a	O
Strategic	O
Defense	O
Initiative	O
satellite	B-Application
orbiting	O
the	O
Earth	O
and	O
must	O
destroy	O
enemy	O
missiles/satellites	O
with	O
its	O
weapons	O
,	O
and	O
when	O
activated	O
the	O
satellite	B-Application
's	O
weapon	O
systems	O
fire	O
at	O
the	O
crosshair	O
present	O
onscreen	O
during	O
play	O
.	O
</s>
<s>
The	O
arcade	O
version	O
features	O
a	O
joystick	B-Device
to	O
control	O
the	O
satellite	B-Application
and	O
a	O
trackball	B-Device
to	O
control	O
the	O
crosshair	O
.	O
</s>
<s>
Home	O
computer	O
versions	O
use	O
different	O
control	O
schemes	O
,	O
such	O
as	O
depressing	O
the	O
fire	O
button	O
to	O
control	O
the	O
crosshair	O
,	O
alternating	O
between	O
controlling	O
the	O
satellite	B-Application
and	O
its	O
weapons	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
use	O
a	O
joystick	B-Device
and	O
mouse	O
in	O
combination	O
to	O
control	O
the	O
satellite	B-Application
and	O
crosshair	O
at	O
the	O
same	O
time	O
,	O
emulating	O
the	O
arcade	O
game	O
's	O
controls	O
.	O
</s>
<s>
During	O
offensive	O
mode	O
the	O
player	O
engages	O
a	O
number	O
of	O
enemies	O
,	O
with	O
the	O
aim	O
of	O
destroying	O
them	O
all	O
without	O
the	O
satellite	B-Application
being	O
destroyed	O
by	O
the	O
enemy	O
.	O
</s>
<s>
In	O
Japan	O
,	O
Game	O
Machine	O
listed	O
SDI	B-Application
on	O
their	O
June	O
1	O
,	O
1987	B-Application
issue	O
as	O
being	O
the	O
sixth	O
most-successful	O
table	O
arcade	O
unit	O
of	O
the	O
month	O
.	O
</s>
