<s>
Entombed	B-Application
is	O
an	O
Atari	B-General_Concept
2600	I-General_Concept
game	O
designed	O
by	O
Tom	O
Sloper	O
and	O
programmed	O
by	O
Steven	O
Sidley	O
.	O
</s>
<s>
It	O
was	O
released	O
in	O
1982	B-Application
by	O
U.S.	O
Games	O
.	O
</s>
<s>
It	O
involves	O
a	O
player	O
moving	O
through	O
a	O
maze	B-Application
and	O
avoiding	O
enemies	O
.	O
</s>
<s>
The	O
game	O
's	O
perplexing	O
maze	B-Application
generation	O
algorithm	O
has	O
attracted	O
academic	O
study	O
.	O
</s>
<s>
The	O
player	O
moves	O
downward	O
through	O
a	O
continuously	O
vertically-scrolling	O
maze	B-Application
with	O
vertical	O
symmetry	O
,	O
trying	O
to	O
get	O
as	O
far	O
as	O
possible	O
while	O
avoiding	O
enemies	O
that	O
move	O
across	O
the	O
screen	O
;	O
if	O
the	O
player	O
contacts	O
a	O
monster	O
,	O
they	O
die	O
and	O
the	O
game	O
is	O
over	O
.	O
</s>
<s>
The	O
maze	B-Application
will	O
continually	O
scroll	O
upwards	O
on	O
the	O
screen	O
,	O
and	O
while	O
the	O
player	O
can	O
move	O
in	O
any	O
direction	O
,	O
this	O
scrolling	O
action	O
may	O
leave	O
the	O
player	O
stuck	O
in	O
a	O
dead-end	O
;	O
if	O
the	O
player	O
's	O
position	O
scrolls	O
off-screen	O
,	O
then	O
the	O
game	O
is	O
also	O
over	O
.	O
</s>
<s>
In	O
two-player	O
mode	O
,	O
both	O
players	O
are	O
in	O
the	O
maze	B-Application
at	O
once	O
.	O
</s>
<s>
The	O
mechanics	O
of	O
how	O
Entombed	B-Application
generated	O
its	O
mazes	B-Application
have	O
been	O
the	O
subject	O
of	O
academic	O
research	O
and	O
some	O
legend	O
,	O
as	O
the	O
maze	B-Application
data	O
itself	O
,	O
if	O
stored	O
directly	O
,	O
was	O
too	O
large	O
to	O
fit	O
within	O
the	O
hardware	O
limitations	O
of	O
the	O
console	O
,	O
even	O
with	O
the	O
left/right	O
symmetry	O
of	O
the	O
mazes	B-Application
.	O
</s>
<s>
Researchers	O
evaluated	O
the	O
game	O
's	O
ROM	O
and	O
discovered	O
that	O
the	O
mazes	B-Application
were	O
generated	O
on-the-fly	O
by	O
the	O
game	O
using	O
the	O
state	O
of	O
five	O
adjacent	O
squares	O
of	O
the	O
maze	B-Application
(	O
wall	O
or	O
open	O
)	O
already	O
generated	O
to	O
determine	O
the	O
next	O
part	O
of	O
the	O
maze	B-Application
through	O
a	O
lookup	B-Data_Structure
table	I-Data_Structure
,	O
including	O
potentially	O
a	O
random	O
state	O
.	O
</s>
<s>
Sometimes	O
the	O
table	O
generates	O
mazes	B-Application
that	O
would	O
be	O
unsolvable	O
without	O
the	O
"	O
make-break	O
"	O
item	O
.	O
</s>
<s>
A	O
2021	O
paper	O
described	O
the	O
algorithm	O
for	O
generating	O
this	O
lookup	B-Data_Structure
table	I-Data_Structure
and	O
a	O
generalization	O
to	O
three-dimensional	O
mazes	B-Application
.	O
</s>
<s>
A	O
2022	O
publication	O
co-authored	O
by	O
Paul	O
Allen	O
Newell	O
,	O
a	O
first-hand	O
participant	O
in	O
the	O
game	O
development	O
,	O
has	O
come	O
closer	O
to	O
settling	O
the	O
debate	O
about	O
the	O
mysteries	O
of	O
the	O
maze	B-Application
algorithm	O
.	O
</s>
