<s>
Citadel	B-Application
is	O
a	O
computer	O
game	O
developed	O
by	O
Michael	O
Jakobsen	O
for	O
the	O
BBC	B-Device
Micro	I-Device
,	O
and	O
released	O
by	O
Superior	B-Device
Software	I-Device
in	O
1985	O
.	O
</s>
<s>
It	O
was	O
also	O
ported	O
to	O
the	O
Acorn	B-Device
Electron	I-Device
.	O
</s>
<s>
Upon	O
returning	O
the	O
crystals	O
,	O
the	O
player	O
must	O
teleport	B-General_Concept
to	O
a	O
separate	O
set	O
of	O
locations	O
to	O
complete	O
the	O
game	O
.	O
</s>
<s>
Citadel	B-Application
was	O
unusual	O
at	O
the	O
time	O
for	O
playing	O
synthesized	O
speech	O
before	O
loading	O
the	O
main	O
game	O
(	O
in	O
part	O
to	O
advertise	O
Superior	B-Device
Software	I-Device
's	O
"	O
Speech	O
!	O
"	O
</s>
<s>
Many	O
BBC	B-Device
Micro	I-Device
gamers	O
regard	O
Citadel	B-Application
as	O
a	O
seminal	O
game	O
and	O
it	O
has	O
spawned	O
social	O
media	O
appreciation	O
pages	O
.	O
</s>
<s>
Citadel	B-Application
has	O
a	O
number	O
of	O
distinctive	O
features	O
.	O
</s>
<s>
The	O
player	O
sprite	O
is	O
not	O
superimposed	O
over	O
objects	O
that	O
it	O
walks	O
"	O
in	O
front	O
"	O
of	O
;	O
rather	O
,	O
the	O
colour	O
of	O
the	O
pixels	O
of	O
the	O
character	O
sprite	O
is	O
overlaid	O
,	O
using	O
an	O
XOR	B-Application
bitwise	O
operation	O
,	O
with	O
the	O
colour	O
of	O
the	O
superimposed	O
object	O
,	O
resulting	O
in	O
a	O
completely	O
different	O
colour	O
.	O
</s>
<s>
These	O
include	O
coloured	O
keys	O
which	O
open	O
doors	O
of	O
the	O
same	O
colour	O
,	O
giving	O
access	O
to	O
other	O
areas	O
of	O
the	O
game	O
;	O
an	O
'	O
ice	O
crystal	O
 '	O
which	O
,	O
whilst	O
carried	O
,	O
causes	O
water	O
in	O
its	O
vicinity	O
to	O
freeze	O
,	O
enabling	O
access	O
to	O
previously	O
inaccessible	O
areas	O
;	O
trampolines	B-General_Concept
which	O
can	O
be	O
jumped	O
on	O
to	O
reach	O
high	O
areas	O
ordinarily	O
out	O
of	O
reach	O
,	O
and	O
many	O
others	O
.	O
</s>
<s>
Most	O
of	O
the	O
items	O
scattered	O
throughout	O
the	O
game	O
are	O
needed	O
to	O
complete	O
it	O
,	O
with	O
the	O
exception	O
of	O
the	O
barrel	O
(	O
which	O
can	O
be	O
used	O
as	O
a	O
platform	O
to	O
jump	O
to	O
a	O
higher	O
area	O
,	O
although	O
the	O
same	O
effect	O
can	O
be	O
achieved	O
with	O
the	O
trampoline	B-General_Concept
)	O
,	O
and	O
the	O
metal	O
bars	O
,	O
which	O
can	O
be	O
taken	O
to	O
the	O
Stonehenge	O
screen	O
to	O
be	O
converted	O
into	O
energy	O
,	O
but	O
add	O
no	O
points	O
to	O
the	O
player	O
's	O
score	O
.	O
</s>
<s>
In	O
order	O
to	O
port	O
the	O
BBC	B-Device
Micro	I-Device
game	O
to	O
the	O
Electron	O
,	O
which	O
had	O
more	O
limited	O
memory	O
constraints	O
,	O
apparently	O
random	O
multicoloured	O
top	O
and	O
bottom	O
borders	O
had	O
to	O
be	O
left	O
on	O
screen	O
.	O
</s>
<s>
Citadel	B-Application
received	O
a	O
great	O
deal	O
of	O
acclaim	O
at	O
the	O
time	O
of	O
its	O
release	O
,	O
and	O
remains	O
one	O
of	O
the	O
classic	O
BBC	B-Device
Micro	I-Device
games	O
.	O
</s>
<s>
The	O
game	O
Palace	B-Application
of	I-Application
Magic	I-Application
,	O
released	O
in	O
1987	O
,	O
used	O
extremely	O
similar	O
gameplay	O
principles	O
,	O
and	O
was	O
in	O
a	O
way	O
a	O
de	O
facto	O
sequel	O
.	O
</s>
<s>
Although	O
subsequent	O
games	O
from	O
Superior	O
,	O
such	O
as	O
Quest	O
,	O
Camelot	B-Application
,	O
Ricochet	B-Application
and	O
Baron	O
,	O
used	O
many	O
of	O
the	O
same	O
elements	O
—	O
though	O
without	O
achieving	O
the	O
same	O
cult	O
status	O
—	O
an	O
official	O
sequel	O
to	O
the	O
game	O
was	O
not	O
released	O
until	O
1993	O
when	O
Superior	O
decided	O
to	O
release	O
The	O
Fort	O
,	O
yet	O
another	O
such	O
game	O
,	O
as	O
Citadel	B-Application
2	I-Application
.	O
</s>
<s>
However	O
,	O
by	O
this	O
time	O
the	O
BBC	B-Device
Micro	I-Device
was	O
declining	O
in	O
popularity	O
—	O
Citadel	B-Application
2	I-Application
,	O
written	O
by	O
"	O
Symo	O
"	O
(	O
Simon	O
Storr	O
)	O
was	O
one	O
of	O
the	O
last	O
BBC	B-Device
Micro	I-Device
games	O
released	O
—	O
and	O
the	O
sequel	O
is	O
little	O
known	O
.	O
</s>
<s>
As	O
with	O
most	O
Superior	B-Device
Software	I-Device
games	O
during	O
this	O
period	O
,	O
there	O
was	O
a	O
prize	O
associated	O
with	O
Citadel	B-Application
.	O
</s>
<s>
Reconstructed	O
source	O
code	O
obtained	O
by	O
disassembling	O
the	O
BBC	B-Device
Model	I-Device
B	I-Device
version	O
of	O
the	O
game	O
was	O
released	O
in	O
October	O
2018	O
.	O
</s>
<s>
Final	O
versions	O
of	O
the	O
original	O
Acorn	B-Device
Electron	I-Device
source	O
code	O
,	O
as	O
well	O
as	O
multiple	O
development	O
versions	O
of	O
the	O
BBC	B-Device
Micro	I-Device
source	O
,	O
were	O
made	O
available	O
by	O
the	O
game	O
's	O
author	O
in	O
December	O
2021	O
with	O
the	O
released	O
package	O
also	O
including	O
various	O
documents	O
related	O
to	O
the	O
game	O
's	O
development	O
.	O
</s>
