<s>
The	B-Application
Sentinel	I-Application
,	O
released	O
in	O
the	O
United	O
States	O
as	O
The	B-Application
Sentry	I-Application
,	O
is	O
a	O
puzzle	O
video	O
game	O
created	O
by	O
Geoff	O
Crammond	O
,	O
published	O
by	O
Firebird	O
in	O
1986	O
for	O
the	O
BBC	B-Device
Micro	I-Device
and	O
converted	O
to	O
the	O
Commodore	O
64	O
(	O
by	O
Crammond	O
himself	O
)	O
,	O
Amstrad	B-Device
CPC	I-Device
(	O
with	O
a	O
cross-compiler	O
written	O
by	O
Crammond	O
)	O
,	O
ZX	B-Operating_System
Spectrum	I-Operating_System
(	O
by	O
Mike	O
Follin	O
)	O
,	O
Atari	B-Device
ST	I-Device
,	O
Amiga	B-Device
(	O
both	O
by	O
Steve	O
Bak	O
)	O
and	O
IBM	O
PC	O
compatibles	O
(	O
by	O
Mark	O
Roll	O
)	O
.	O
</s>
<s>
The	B-Application
Sentinel	I-Application
was	O
among	O
the	O
first	O
games	O
to	O
use	O
solid-filled	O
3D	O
graphics	O
on	O
home	O
computers	O
.	O
</s>
<s>
The	O
IBM	O
PC	O
port	O
supports	O
VGA	B-Protocol
graphics	I-Protocol
,	O
with	O
an	O
additional	O
lighting	O
effect	O
:	O
objects	O
and	O
terrain	O
become	O
darker	O
the	O
farther	O
away	O
they	O
are	O
from	O
the	O
point	O
of	O
view	O
.	O
</s>
<s>
The	O
Amiga	B-Device
port	O
has	O
a	O
sampled	O
soundtrack	O
by	O
David	O
Whittaker	O
.	O
</s>
<s>
In	O
The	B-Application
Sentinel	I-Application
,	O
the	O
player	O
takes	O
the	O
role	O
of	O
a	O
Synthoid	O
(	O
called	O
just	O
"	O
robot	O
"	O
in	O
the	O
US	O
version	O
)	O
,	O
a	O
telepathic	B-Protocol
robot	O
who	O
has	O
to	O
take	O
control	O
of	O
a	O
number	O
of	O
surreal	O
,	O
checkered	O
landscapes	O
of	O
hills	O
and	O
valleys	O
,	O
by	O
climbing	O
from	O
the	O
lowest	O
spot	O
,	O
where	O
the	O
hunt	O
begins	O
,	O
to	O
the	O
highest	O
platform	O
,	O
over	O
which	O
the	B-Application
Sentinel	I-Application
looms	O
.	O
</s>
<s>
It	O
is	O
also	O
used	O
to	O
hyperspace	O
to	O
the	O
next	O
level	O
when	O
the	O
player	O
has	O
reached	O
the	B-Application
Sentinel	I-Application
's	O
height	O
.	O
</s>
<s>
While	O
doing	O
so	O
,	O
the	O
player	O
must	O
watch	O
for	O
the	O
rotation	O
of	O
the	B-Application
Sentinel	I-Application
and	O
be	O
careful	O
not	O
to	O
stand	O
in	O
an	O
area	O
which	O
the	B-Application
Sentinel	I-Application
can	O
see	O
,	O
or	O
else	O
it	O
will	O
start	O
absorbing	O
energy	O
from	O
the	O
Synthoid	O
,	O
and	O
when	O
the	O
energy	O
is	O
gone	O
,	O
the	O
game	O
is	O
over	O
.	O
</s>
<s>
In	O
order	O
to	O
absorb	O
the	B-Application
Sentinel	I-Application
,	O
the	O
player	O
must	O
create	O
a	O
stack	O
of	O
boulders	O
of	O
sufficient	O
height	O
that	O
the	O
Synthoid	O
on	O
top	O
can	O
look	O
down	O
on	O
the	B-Application
Sentinel	I-Application
's	O
platform	O
.	O
</s>
<s>
When	O
the	B-Application
Sentinel	I-Application
has	O
been	O
absorbed	O
,	O
the	O
player	O
may	O
no	O
longer	O
absorb	O
any	O
energy	O
from	O
the	O
landscape	O
,	O
although	O
objects	O
may	O
be	O
created	O
as	O
normal	O
.	O
</s>
<s>
In	O
later	O
levels	O
,	O
the	B-Application
Sentinel	I-Application
is	O
assisted	O
by	O
a	O
number	O
of	O
Sentries	O
.	O
</s>
<s>
They	O
behave	O
exactly	O
like	O
the	B-Application
Sentinel	I-Application
,	O
but	O
absorbing	O
them	O
is	O
not	O
necessary	O
to	O
complete	O
the	O
level	O
.	O
</s>
<s>
Unlike	O
the	B-Application
Sentinel	I-Application
,	O
the	B-Application
Sentries	I-Application
do	O
not	O
stand	O
on	O
a	O
platform	O
but	O
on	O
ordinary	O
squares	O
.	O
</s>
<s>
If	O
the	B-Application
Sentinel	I-Application
or	O
Sentry	O
cannot	O
see	O
the	O
square	O
the	O
Synthoid	O
is	O
standing	O
on	O
,	O
but	O
its	O
head	O
is	O
visible	O
and	O
there	O
are	O
trees	O
in	O
the	O
vicinity	O
,	O
it	O
may	O
transform	O
one	O
of	O
them	O
into	O
a	O
Meanie	O
,	O
which	O
will	O
force	O
the	O
Synthoid	O
to	O
hyperspace	O
and	O
lose	O
3	O
units	O
of	O
energy	O
.	O
</s>
<s>
If	O
the	O
Meanie	O
cannot	O
see	O
the	O
player	O
's	O
square	O
after	O
a	O
full	O
rotation	O
,	O
it	O
will	O
turn	O
back	O
into	O
a	O
tree	O
and	O
the	B-Application
Sentinel	I-Application
or	O
Sentry	O
will	O
resume	O
rotation	O
.	O
</s>
<s>
The	O
rotation	O
of	O
the	B-Application
Sentinel	I-Application
and	O
the	B-Application
Sentries	I-Application
is	O
slow	O
and	O
predictable	O
.	O
</s>
<s>
If	O
either	O
the	B-Application
Sentinel	I-Application
or	O
the	B-Application
Sentries	I-Application
come	O
across	O
a	O
source	O
of	O
energy	O
(	O
boulders	O
or	O
a	O
synthoid	O
)	O
,	O
their	O
rotation	O
stops	O
while	O
they	O
absorb	O
the	O
energy	O
,	O
one	O
unit	O
at	O
a	O
time	O
.	O
</s>
<s>
A	O
level	O
is	O
won	O
by	O
absorbing	O
the	B-Application
Sentinel	I-Application
off	O
its	O
platform	O
,	O
creating	O
a	O
new	O
Synthoid	O
in	O
the	O
place	O
of	O
the	B-Application
Sentinel	I-Application
,	O
transferring	O
the	O
consciousness	O
to	O
it	O
and	O
hyperspacing	O
to	O
a	O
new	O
level	O
.	O
</s>
<s>
The	B-Application
Sentinel	I-Application
has	O
no	O
ending	O
sequence	O
;	O
upon	O
completion	O
of	O
the	O
last	O
level	O
,	O
the	O
player	O
is	O
looped	O
back	O
to	O
level	O
1	O
.	O
</s>
<s>
Computer	O
Gaming	O
World	O
called	O
the	O
Commodore	O
64	O
version	O
of	O
The	B-Application
Sentinel	I-Application
"	O
outstanding	O
and	O
addictive	O
...	O
</s>
<s>
The	O
ZX	B-Operating_System
Spectrum	I-Operating_System
version	O
received	O
a	O
CRASH	O
Smash	O
award	O
,	O
the	O
magazine	O
praising	O
its	O
originality	O
,	O
atmosphere	O
and	O
tension	O
.	O
</s>
<s>
The	O
Amiga	B-Device
version	O
was	O
ranked	O
the	O
20th	O
best	O
game	O
of	O
all	O
time	O
by	O
Amiga	B-Device
Power	O
;	O
one	O
of	O
the	O
50	O
best	O
computer	O
games	O
ever	O
by	O
PC	O
Format	O
,	O
who	O
called	O
it	O
"	O
straight	O
out	O
of	O
left	O
field	O
"	O
and	O
"	O
inspired	O
"	O
;	O
and	O
the	O
53rd	O
best	O
game	O
of	O
all	O
time	O
by	O
Next	O
Generation	O
,	O
who	O
cited	O
the	O
"	O
Absolute	O
,	O
paranoid	O
,	O
scrambling	O
tension	O
"	O
experienced	O
by	O
the	O
players	O
as	O
they	O
try	O
to	O
avoid	O
the	B-Application
sentinel	I-Application
's	O
gaze	O
.	O
</s>
<s>
In	O
1998	O
,	O
the	O
real	O
sequel	O
called	O
Sentinel	O
Returns	O
was	O
released	O
for	O
Windows	O
and	O
PlayStation	B-Device
.	O
</s>
<s>
Archipelagos	B-Application
(	O
1989	O
)	O
has	O
different	O
gameplay	O
but	O
a	O
similar	O
surreal	O
environment	O
.	O
</s>
<s>
A	O
number	O
of	O
unofficial	O
remakes	O
and	O
variants	O
of	O
The	B-Application
Sentinel	I-Application
have	O
been	O
written	O
,	O
such	O
as	O
Sentry	O
(	O
1989	O
,	O
MS-DOS	O
)	O
,	O
Zenith	O
(	O
2005	O
,	O
Windows	O
freeware	O
)	O
,	O
and	O
Augmentinel	O
(	O
2019	O
,	O
Windows	O
freeware	O
)	O
.	O
</s>
