<s>
NetHack	B-Application
is	O
an	O
open	B-License
source	I-License
single-player	O
roguelike	O
video	O
game	O
,	O
first	O
released	O
in	O
1987	O
and	O
maintained	O
by	O
the	O
NetHack	B-Application
DevTeam	O
.	O
</s>
<s>
The	O
game	O
is	O
a	O
fork	B-Application
of	O
the	O
1982	O
game	O
Hack	B-Application
,	O
itself	O
inspired	O
by	O
the	O
1980	O
game	O
Rogue	B-Application
.	O
</s>
<s>
The	O
player	O
takes	O
the	O
role	O
of	O
one	O
of	O
several	O
pre-defined	O
character	O
classes	O
to	O
descend	O
through	O
multiple	O
dungeon	O
floors	O
,	O
fighting	O
monsters	O
and	O
collecting	O
treasure	O
,	O
to	O
recover	O
the	O
"	O
Amulet	B-Application
of	I-Application
Yendor	I-Application
"	O
at	O
the	O
lowest	O
floor	O
and	O
then	O
escape	O
.	O
</s>
<s>
As	O
an	O
exemplar	O
of	O
the	O
traditional	O
"	O
roguelike	O
"	O
game	O
,	O
NetHack	B-Application
features	O
turn-based	O
,	O
grid-based	O
hack	B-Application
and	I-Application
slash	I-Application
dungeon	O
crawling	O
gameplay	O
,	O
procedurally	O
generated	O
dungeons	O
and	O
treasure	O
,	O
and	O
permadeath	B-Application
,	O
requiring	O
the	O
player	O
to	O
restart	O
the	O
game	O
anew	O
should	O
the	O
player	O
character	O
die	O
.	O
</s>
<s>
The	O
game	O
uses	O
simple	O
ASCII	B-Protocol
graphics	O
by	O
default	O
so	O
as	O
to	O
display	O
readily	O
on	O
a	O
wide	O
variety	O
of	O
computer	B-General_Concept
displays	I-General_Concept
,	O
but	O
can	O
use	O
curses	B-Application
with	O
box-drawing	O
characters	O
,	O
as	O
well	O
as	O
substitute	O
graphical	O
tilesets	O
on	O
machines	O
with	O
graphics	O
.	O
</s>
<s>
While	O
Rogue	B-Application
,	O
Hack	B-Application
and	O
other	O
earlier	O
roguelikes	O
stayed	O
true	O
to	O
a	O
high	O
fantasy	O
setting	O
,	O
NetHack	B-Application
introduced	O
humorous	O
and	O
anachronistic	O
elements	O
over	O
time	O
,	O
including	O
popular	O
cultural	O
reference	O
to	O
works	O
such	O
as	O
Discworld	B-Application
and	O
Raiders	B-Application
of	I-Application
the	I-Application
Lost	I-Application
Ark	I-Application
.	O
</s>
<s>
Comparing	O
it	O
with	O
Rogue	B-Application
,	O
Engadgets	B-Application
Justin	O
Olivetti	O
wrote	O
that	O
it	O
took	O
its	O
exploration	O
aspect	O
and	O
made	O
it	O
far	O
richer	O
with	O
an	O
encyclopedia	O
of	O
objects	O
,	O
a	O
larger	O
vocabulary	O
,	O
a	O
wealth	O
of	O
pop	O
culture	O
references	O
,	O
and	O
a	O
puzzler	O
's	O
attitude	O
.	O
</s>
<s>
There	O
are	O
traditional	O
fantasy	O
roles	O
such	O
as	O
knight	O
,	O
wizard	O
,	O
rogue	B-Application
,	O
and	O
priest	O
;	O
but	O
there	O
are	O
also	O
unusual	O
roles	O
,	O
including	O
archaeologist	O
,	O
tourist	O
,	O
and	O
caveman	B-Algorithm
.	O
</s>
<s>
To	O
win	O
the	O
game	O
,	O
the	O
player	O
must	O
retrieve	O
the	O
Amulet	B-Application
of	I-Application
Yendor	I-Application
,	O
found	O
at	O
the	O
lowest	O
level	O
of	O
the	O
dungeon	O
,	O
and	O
offer	O
it	O
to	O
their	O
deity	O
.	O
</s>
<s>
Successful	O
completion	O
of	O
this	O
task	O
rewards	O
the	O
player	O
with	O
the	O
gift	O
of	O
immortality	B-Application
,	O
and	O
the	O
player	O
is	O
said	O
to	O
"	O
ascend	O
"	O
,	O
attaining	O
the	O
status	O
of	O
demigod	B-Language
.	O
</s>
<s>
There	O
are	O
3	O
major	O
antagonists	O
in	O
NetHack	B-Application
;	O
the	O
Luciferesque	B-Algorithm
god	O
Moloch	O
,	O
who	O
stole	O
the	O
Amulet	B-Application
Of	I-Application
Yendor	I-Application
from	O
the	O
creator	O
god	O
Marduk	O
,	O
the	O
high	O
priest/priestess	O
of	O
Moloch	O
,	O
who	O
holds	O
the	O
Amulet	B-Application
of	I-Application
Yendor	I-Application
,	O
and	O
the	O
most	O
prominent	O
antagonist	O
,	O
the	O
Wizard	O
of	O
Yendor	B-Application
,	O
who	O
will	O
stalk	O
the	O
player	O
throughout	O
the	O
rest	O
of	O
the	O
game	O
after	O
the	O
first	O
encounter	O
by	O
resurrecting	O
and	O
attacking	O
them	O
periodically	O
.	O
</s>
<s>
NetHack'''s	O
dungeon	O
spans	O
about	O
fifty	O
primary	O
levels	O
,	O
most	O
of	O
which	O
are	O
procedurally	O
generated	O
when	O
the	O
player	O
character	O
enters	O
them	O
for	O
the	O
first	O
time	O
.	O
</s>
<s>
Levels	O
,	O
once	O
generated	O
,	O
remained	O
persistent	O
,	O
in	O
contrast	O
to	O
games	O
that	O
followed	O
Moria-style	O
of	O
level	O
generation	O
.	O
</s>
<s>
250px|thumb|A	O
player	O
's	O
inventoryNetHack	O
features	O
a	O
variety	O
of	O
items	O
:	O
weapons	O
(	O
melee	O
or	O
ranged	O
)	O
,	O
armor	O
to	O
protect	O
the	O
player	O
,	O
scrolls	B-Operating_System
and	O
spellbooks	O
to	O
read	O
,	O
potions	O
to	O
quaff	O
,	O
wands	O
,	O
rings	O
,	O
amulets	O
,	O
and	O
an	O
assortment	O
of	O
tools	O
,	O
such	O
as	O
keys	O
and	O
lamps.NetHack	O
'	O
s	O
identification	O
of	O
items	O
is	O
almost	O
identical	O
to	O
Rogue	B-Application
's	O
.	O
</s>
<s>
For	O
instance	O
,	O
all	O
"	O
scrolls	B-Operating_System
of	O
enchant	O
weapon	O
"	O
may	O
be	O
labeled	O
"	O
TEMOV	O
"	O
,	O
and	O
once	O
one	O
has	O
been	O
identified	O
,	O
all	O
"	O
scrolls	B-Operating_System
of	O
enchant	O
weapon	O
"	O
found	O
later	O
will	O
be	O
labeled	O
unambiguously	O
as	O
such	O
.	O
</s>
<s>
As	O
in	O
many	O
other	O
roguelike	O
games	O
,	O
all	O
items	O
in	O
NetHack	B-Application
are	O
either	O
"	O
blessed	O
"	O
,	O
"	O
uncursed	O
"	O
,	O
or	O
"	O
cursed	O
"	O
.	O
</s>
<s>
Where	O
an	O
object	O
would	O
bestow	O
an	O
effect	O
upon	O
the	O
character	O
,	O
a	O
curse	B-Application
will	O
generally	O
make	O
the	O
effect	O
harmful	O
,	O
or	O
increase	O
the	O
amount	O
of	O
harm	O
done	O
.	O
</s>
<s>
As	O
in	O
other	O
roguelike	O
games	O
,	O
NetHack	B-Application
features	O
permadeath	B-Application
:	O
expired	O
characters	O
cannot	O
be	O
revived	O
.	O
</s>
<s>
Although	O
NetHack	B-Application
can	O
be	O
completed	O
without	O
any	O
artificial	O
limitations	O
,	O
experienced	O
players	O
can	O
attempt	O
"	O
conducts	O
"	O
for	O
an	O
additional	O
challenge	O
.	O
</s>
<s>
Such	O
deaths	O
are	O
considered	O
part	O
of	O
learning	O
to	O
play	O
NetHack	B-Application
as	O
to	O
avoid	O
conditions	O
where	O
the	O
same	O
death	O
may	O
happen	O
again.NetHack	O
does	O
allow	O
players	O
to	O
save	O
the	O
game	O
so	O
that	O
one	O
does	O
not	O
have	O
to	O
complete	O
the	O
game	O
in	O
one	O
session	O
,	O
but	O
on	O
opening	O
a	O
new	O
game	O
,	O
the	O
previous	O
save	O
file	O
is	O
subsequently	O
wiped	O
as	O
to	O
enforce	O
the	O
permadeath	B-Application
option	O
.	O
</s>
<s>
While	O
these	O
help	O
the	O
player	O
to	O
learn	O
the	O
game	O
and	O
get	O
around	O
limits	O
of	O
permadeath	B-Application
,	O
both	O
are	O
considered	O
forms	O
of	O
cheating	O
the	O
game	O
.	O
</s>
<s>
A	O
number	O
of	O
NetHack	B-Application
fan	O
sites	O
and	O
discussion	O
forums	O
offer	O
lists	O
of	O
game	O
secrets	O
known	O
as	O
"	O
spoilers	O
"	O
.	O
</s>
<s>
Interface	O
elements	O
such	O
as	O
the	O
environment	O
,	O
entities	O
,	O
and	O
objects	O
are	O
represented	O
by	O
arrangements	O
of	O
ASCII	B-Protocol
or	O
Extended	B-Protocol
ASCII	I-Protocol
glyphs	O
,	O
"	O
DECgraphics	O
"	O
,	O
or	O
"	O
IBMgraphics	O
"	O
mode	O
.	O
</s>
<s>
Apart	O
from	O
the	O
original	O
termcap	B-Application
interface	O
shown	O
above	O
,	O
there	O
are	O
other	O
interfaces	O
that	O
replace	O
standard	O
screen	O
representations	O
with	O
two-dimensional	O
images	O
,	O
or	O
tiles	B-Application
,	O
collectively	O
known	O
as	O
"	O
tiles	B-Application
mode	O
"	O
.	O
</s>
<s>
Graphic	B-Application
interfaces	I-Application
of	O
this	O
kind	O
have	O
been	O
successfully	O
implemented	O
on	O
the	O
Amiga	B-Device
,	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
the	O
Microsoft	B-Application
Windows	I-Application
GUI	B-Application
,	O
the	O
Qt	B-Language
toolkit	I-Language
,	O
and	O
the	O
GNOME	B-Application
libraries	O
.	O
</s>
<s>
Enhanced	O
graphical	O
options	O
also	O
exist	O
,	O
such	O
as	O
the	O
isometric	B-Application
perspective	I-Application
of	O
Falcon	B-Application
's	I-Application
Eye	I-Application
and	O
Vulture	B-Application
's	I-Application
Eye	I-Application
,	O
or	O
the	O
three-dimensional	O
rendering	O
that	O
noegnud	O
offers	O
.	O
</s>
<s>
Vulture	B-Application
's	I-Application
Eye	I-Application
is	O
a	O
fork	B-Application
of	O
the	O
now	O
defunct	O
Falcon	B-Application
's	I-Application
Eye	I-Application
project	O
.	O
</s>
<s>
Vulture	B-Application
's	I-Application
Eye	I-Application
adds	O
additional	O
graphics	O
,	O
sounds	O
,	O
bug	O
fixes	O
and	O
performance	O
enhancements	O
and	O
is	O
under	O
active	O
development	O
in	O
an	O
open	O
collaborative	O
environment	O
.	O
</s>
<s>
History	O
and	O
development	O
NetHack	B-Application
is	O
a	O
software	O
derivative	O
of	O
Hack	B-Application
,	O
which	O
itself	O
was	O
inspired	O
by	O
Rogue	B-Application
.	O
</s>
<s>
Hack	B-Application
was	O
created	O
by	O
students	O
Jay	O
Fenlason	O
,	O
Kenny	O
Woodland	O
,	O
Mike	O
Thome	O
,	O
and	O
Jonathan	B-Application
Payne	I-Application
at	O
Lincoln-Sudbury	O
Regional	O
High	O
School	O
as	O
part	O
of	O
a	O
computer	O
class	O
,	O
after	O
seeing	O
and	O
playing	O
Rogue	B-Application
at	O
the	O
University	O
of	O
California	O
Berkeley	O
computer	O
labs.Craddock	O
2015	O
,	O
Chapter	O
5	O
:	O
"	O
When	O
the	O
Inmates	O
Run	O
the	O
Asylum	O
-	O
Hack-ing	O
at	O
Lincoln-Sudbury	O
High	O
School	O
"	O
The	O
group	O
had	O
tried	O
to	O
get	O
the	O
source	O
code	O
of	O
Rogue	B-Application
from	O
Glenn	O
Wichman	O
and	O
Michael	B-Application
Toy	I-Application
to	O
build	O
upon	O
,	O
but	O
Wichman	O
and	O
Toy	O
had	O
refused	O
,	O
forcing	O
the	O
students	O
to	O
build	O
the	O
dungeon-creation	O
routines	O
on	O
their	O
own	O
.	O
</s>
<s>
As	O
such	O
,	O
the	O
game	O
was	O
named	O
Hack	B-Application
in	O
part	O
for	O
the	O
hack-and-slash	B-Application
gameplay	O
and	O
that	O
the	O
code	O
to	O
generate	O
the	O
dungeons	O
was	O
considered	O
a	O
programming	B-Architecture
hack	I-Architecture
.	O
</s>
<s>
Fenlason	O
provided	O
the	O
source	O
code	O
to	O
a	O
local	O
USENIX	B-Operating_System
conference	O
,	O
and	O
eventually	O
it	O
was	O
uploaded	O
to	O
USENET	B-Application
newsgroups	I-Application
.	O
</s>
<s>
Hack	B-Application
did	O
not	O
have	O
any	O
formal	O
maintainer	O
and	O
while	O
one	O
person	O
was	O
generally	O
recognized	O
to	O
hold	O
the	O
main	O
code	O
to	O
the	O
current	O
version	O
of	O
Hack	B-Application
,	O
many	O
software	B-Application
forks	I-Application
emerged	O
from	O
the	O
unorganized	O
development	O
of	O
the	O
game	O
.	O
</s>
<s>
Eventually	O
,	O
Mike	O
Stephenson	O
took	O
on	O
the	O
role	O
as	O
maintainer	O
of	O
the	O
Hack	B-Application
source	O
code	O
.	O
</s>
<s>
At	O
this	O
point	O
,	O
he	O
decided	O
to	O
create	O
a	O
new	O
fork	B-Application
of	O
the	O
game	O
,	O
bringing	O
in	O
novel	O
ideas	O
from	O
Izchak	O
Miller	O
,	O
a	O
philosophy	O
professor	O
at	O
University	O
of	O
Pennsylvania	O
,	O
and	O
Janet	O
Walz	O
,	O
another	O
computer	O
hacker	O
.	O
</s>
<s>
They	O
called	O
themselves	O
the	O
DevTeam	O
and	O
renamed	O
their	O
branch	O
NetHack	B-Application
since	O
their	O
collaboration	O
work	O
was	O
done	O
over	O
the	O
Internet.Craddock	O
2015	O
,	O
Chapter	O
6	O
:	O
"	O
It	O
Takes	O
a	O
Village	O
:	O
Raising	O
NetHack	B-Application
"	O
They	O
expanded	O
the	O
bestiary	O
and	O
other	O
objects	O
in	O
the	O
game	O
,	O
and	O
drew	O
from	O
other	O
sources	O
outside	O
of	O
the	O
high	O
fantasy	O
setting	O
,	O
such	O
as	O
from	O
Discworld	B-Application
with	O
the	O
introduction	O
of	O
the	O
tourist	O
character	O
class	O
.	O
</s>
<s>
Knowing	O
of	O
the	O
multiple	O
forks	B-Application
of	O
Hack	B-Application
that	O
existed	O
,	O
the	O
DevTeam	O
established	O
a	O
principle	O
that	O
while	O
the	O
game	O
was	O
open	B-License
source	I-License
and	O
anyone	O
could	O
create	O
a	O
fork	B-Application
as	O
a	O
new	O
project	O
,	O
only	O
a	O
few	O
select	O
members	O
in	O
the	O
DevTeam	O
could	O
make	O
modifications	O
to	O
the	O
main	O
source	O
repository	O
of	O
the	O
game	O
,	O
so	O
that	O
players	O
could	O
be	O
assured	O
that	O
the	O
DevTeam	O
's	O
release	O
was	O
the	O
legitimate	O
version	O
of	O
NetHack	B-Application
.	O
</s>
<s>
The	O
DevTeam	O
's	O
first	O
release	O
of	O
NetHack	B-Application
was	O
on	O
28	O
July	O
1987	O
.	O
</s>
<s>
The	O
core	O
DevTeam	O
had	O
expanded	O
with	O
the	O
release	O
of	O
NetHack	B-Application
3.0	O
in	O
July	O
1989	O
.	O
</s>
<s>
Subsequent	O
updates	O
from	O
the	O
DevTeam	O
included	O
new	O
tilesets	O
and	O
compatibility	O
with	O
variants	O
of	O
Mac	B-Application
OS	I-Application
,	O
but	O
no	O
major	O
updates	O
to	O
the	O
game	O
had	O
been	O
made	O
.	O
</s>
<s>
Stephenson	O
said	O
that	O
despite	O
the	O
number	O
of	O
roguelike	O
titles	O
that	O
had	O
emerged	O
since	O
the	O
v3.4.3	O
release	O
,	O
they	O
saw	O
that	O
NetHack	B-Application
was	O
still	O
being	O
talked	O
about	O
online	O
in	O
part	O
due	O
to	O
its	O
high	O
degree	O
of	O
portability	O
,	O
and	O
decided	O
to	O
continue	O
its	O
development	O
.	O
</s>
<s>
The	O
update	O
came	O
shortly	O
after	O
the	O
death	O
of	O
Terry	O
Pratchett	O
,	O
whose	O
Discworld	B-Application
had	O
been	O
influential	O
on	O
the	O
game	O
,	O
and	O
the	O
new	O
update	O
included	O
a	O
tribute	O
to	O
him	O
.	O
</s>
<s>
With	O
the	O
v3.6.0	O
release	O
,	O
NetHack	B-Application
remains	O
"	O
one	O
of	O
the	O
oldest	O
games	O
still	O
being	O
developed	O
"	O
.	O
</s>
<s>
A	O
public	O
read-only	O
mirror	O
of	O
NetHack	B-Application
git	B-Application
repository	O
was	O
made	O
available	O
on	O
10	O
February	O
2016	O
.	O
</s>
<s>
,	O
the	O
official	O
source	O
release	O
supports	O
the	O
following	O
systems	O
:	O
Windows	B-Application
,	O
Linux	B-Application
,	O
macOS	B-Application
,	O
Windows	B-Operating_System
CE	I-Operating_System
,	O
OS/2	B-Application
,	O
Unix	B-Application
(	O
BSD	B-Operating_System
,	O
System	B-Operating_System
V	I-Operating_System
,	O
Solaris	B-Application
,	O
HP-UX	B-Application
)	O
,	O
BeOS	B-Application
,	O
and	O
VMS	B-Operating_System
.	O
</s>
<s>
Licensing	O
,	O
ports	O
,	O
and	O
derivative	O
portsNetHack	O
is	O
released	O
under	O
the	O
NetHack	B-Application
General	B-License
Public	I-License
License	I-License
,	O
which	O
was	O
written	O
in	O
1989	O
by	O
Mike	O
Stephenson	O
,	O
patterned	O
after	O
the	O
GNU	B-Application
bison	I-Application
license	O
(	O
which	O
was	O
written	O
by	O
Richard	O
Stallman	O
in	O
1988	O
)	O
.GNU	O
Bison	B-Application
is	O
no	O
longer	O
distributed	O
under	O
the	O
original	O
Bison	B-Application
license	O
;	O
it	O
has	O
been	O
distributed	O
under	O
an	O
extension	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
since	O
at	O
least	O
1991	O
.	O
</s>
<s>
Like	O
the	O
Bison	B-Application
license	O
,	O
and	O
Stallman	O
's	O
later	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
,	O
the	O
NetHack	B-Application
license	O
was	O
written	O
to	O
allow	O
the	O
free	O
sharing	O
and	O
modification	O
of	O
the	O
source	O
code	O
under	O
its	O
protection	O
.	O
</s>
<s>
The	O
NetHack	B-Application
General	B-License
Public	I-License
License	I-License
is	O
a	O
copyleft	B-License
software	B-License
license	I-License
certified	O
as	O
an	O
open	B-License
source	I-License
license	O
by	O
the	O
Open	B-License
Source	I-License
Initiative	O
.	O
</s>
<s>
The	O
NetHack	B-Application
General	B-License
Public	I-License
License	I-License
allows	O
anyone	O
to	O
port	O
the	O
game	O
to	O
a	O
platform	O
not	O
supported	O
by	O
the	O
official	O
DevTeam	O
,	O
provided	O
that	O
they	O
use	O
the	O
same	O
license	O
.	O
</s>
<s>
The	O
license	O
also	O
allows	O
for	O
software	B-Application
forks	I-Application
as	O
long	O
as	O
they	O
are	O
distributed	O
under	O
the	O
same	O
license	O
,	O
except	O
that	O
the	O
creator	O
of	O
a	O
derivative	O
work	O
is	O
allowed	O
to	O
offer	O
warranty	O
protection	O
on	O
the	O
new	O
work	O
.	O
</s>
<s>
This	O
has	O
also	O
allowed	O
source	O
code	B-Application
forks	I-Application
of	O
NetHack	B-Application
including	O
Slash'EM	B-Application
,	O
UnNetHack	O
,	O
and	O
dNethack	O
.	O
</s>
<s>
Bugs	O
,	O
humorous	O
messages	O
,	O
stories	O
,	O
experiences	O
,	O
and	O
ideas	O
for	O
the	O
next	O
version	O
are	O
discussed	O
on	O
the	O
Usenet	B-Application
newsgroup	I-Application
rec.games.roguelike.nethack	O
.	O
</s>
<s>
A	O
public	O
server	O
at	O
nethack.alt.org,	O
commonly	O
known	O
as	O
"	O
NAO	O
"	O
,	O
gives	O
players	O
access	O
to	O
NetHack	B-Application
through	O
a	O
Telnet	B-Protocol
or	O
SSH	B-Protocol
interface	O
.	O
</s>
<s>
Ebonhack	O
connects	O
to	O
NAO	O
with	O
a	O
graphical	O
tiles-based	O
interface	O
.	O
</s>
<s>
During	O
the	O
whole	O
month	O
of	O
November	O
,	O
the	O
annual	O
/dev/null	O
NetHack	B-Application
Tournament	O
took	O
place	O
every	O
year	O
from	O
1999	O
to	O
2016	O
.	O
</s>
<s>
The	O
November	O
NetHack	B-Application
Tournament	O
,	O
initially	O
conceived	O
as	O
a	O
one-time	O
tribute	O
to	O
devnull	O
,	O
has	O
taken	O
place	O
each	O
year	O
since	O
2018	O
.	O
</s>
<s>
The	B-Application
Facebook	I-Application
artificial	B-Application
intelligence	I-Application
(	O
AI	B-Application
)	O
research	O
team	O
,	O
along	O
with	O
researchers	O
at	O
the	O
University	O
of	O
Oxford	O
,	O
New	O
York	O
University	O
,	O
the	O
Imperial	O
College	O
London	O
,	O
and	O
University	O
College	O
London	O
,	O
developed	O
an	O
open-source	B-License
platform	O
called	O
the	O
NetHack	B-Application
Learning	O
Environment	O
,	O
designed	O
to	O
teach	O
AI	B-Application
agents	O
to	O
play	O
NetHack	B-Application
.	O
</s>
<s>
The	O
base	O
environment	O
is	O
able	O
to	O
maneuver	O
the	O
agent	O
and	O
fight	O
its	O
way	O
through	O
dungeons	O
,	O
but	O
the	O
team	O
seeks	O
community	O
help	O
to	O
build	O
an	O
AI	B-Application
on	O
the	O
complexities	O
of	O
NetHack	B-Application
interconnected	O
systems	O
,	O
using	O
implicit	O
knowledge	O
that	O
comes	O
from	O
player-made	O
resources	O
,	O
thus	O
giving	O
a	O
means	O
for	O
programmers	O
to	O
hook	O
into	O
the	O
environment	O
with	O
additional	O
resources	O
.	O
</s>
<s>
Facebook	B-Application
's	O
research	O
led	O
the	O
company	O
to	O
pose	O
NetHack	B-Application
as	O
a	O
grand	O
challenge	O
in	O
AI	B-Application
in	O
June	O
2021	O
,	O
in	O
part	O
due	O
to	O
the	O
game	O
's	O
permadeath	B-Application
and	O
inability	O
to	O
experiment	O
with	O
the	O
environment	O
without	O
creating	O
a	O
reaction	O
.	O
</s>
