<s>
Portal	B-Application
2	I-Application
is	O
a	O
2011	O
puzzle-platform	O
video	O
game	O
developed	O
by	O
Valve	O
for	O
Windows	O
,	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
Linux	B-Application
,	O
PlayStation	B-Operating_System
3	I-Operating_System
,	O
and	O
Xbox	B-Operating_System
360	I-Operating_System
.	O
</s>
<s>
The	O
digital	B-Device
PC	I-Device
version	O
is	O
distributed	O
online	O
by	O
Valve	O
's	O
Steam	B-Application
service	I-Application
,	O
while	O
all	O
retail	O
editions	O
were	O
distributed	O
by	O
Electronic	O
Arts	O
.	O
</s>
<s>
A	O
port	O
for	O
the	O
Nintendo	B-Application
Switch	I-Application
was	O
included	O
as	O
part	O
of	O
Portal	B-Application
:	O
Companion	O
Collection	O
.	O
</s>
<s>
Like	O
the	O
original	O
Portal	B-Application
(	O
2007	O
)	O
,	O
players	O
solve	O
puzzles	O
by	O
placing	O
portals	B-Application
and	O
teleporting	O
between	O
them	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
adds	O
features	O
including	O
tractor	O
beams	O
,	O
lasers	O
,	O
light	O
bridges	O
,	O
and	O
paint-like	O
gels	O
that	O
alter	O
player	O
movement	O
or	O
allow	O
portals	B-Application
to	O
be	O
placed	O
on	O
any	O
surface	O
.	O
</s>
<s>
Valve	O
announced	O
Portal	B-Application
2	I-Application
in	O
March	O
2010	O
,	O
and	O
promoted	O
it	O
with	O
alternate	O
reality	O
games	O
including	O
the	B-Application
Potato	I-Application
Sack	I-Application
,	O
a	O
collaboration	O
with	O
several	O
independent	O
game	O
developers	O
.	O
</s>
<s>
After	O
release	O
,	O
Valve	O
released	O
downloadable	B-Protocol
content	I-Protocol
and	O
a	O
simplified	O
map	O
editor	O
to	O
allow	O
players	O
to	O
create	O
and	O
share	O
levels	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
received	O
critical	O
acclaim	O
for	O
its	O
gameplay	O
,	O
balanced	O
learning	B-General_Concept
curve	I-General_Concept
,	O
pacing	O
,	O
dark	O
humor	O
,	O
writing	O
,	O
and	O
acting	O
.	O
</s>
<s>
Like	O
its	B-Application
predecessor	I-Application
,	O
it	O
has	O
been	O
described	O
as	O
one	O
of	O
the	O
greatest	O
video	O
games	O
ever	O
made	O
by	O
numerous	O
publications	O
and	O
critics	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
is	O
a	O
first-person	O
perspective	O
puzzle	O
game	O
.	O
</s>
<s>
Gameplay	O
revolves	O
around	O
the	O
use	O
of	O
the	O
Aperture	O
Science	O
Handheld	O
Portal	B-Application
Device	O
,	O
which	O
can	O
create	O
a	O
pair	O
of	O
two	O
portals	B-Application
on	O
suitable	O
surfaces	O
through	O
which	O
the	O
player	O
or	O
objects	O
can	O
pass	O
through	O
.	O
</s>
<s>
Characters	O
can	O
use	O
these	O
portals	B-Application
to	O
move	O
between	O
rooms	O
or	O
to	O
"	O
fling	O
"	O
objects	O
or	O
themselves	O
across	O
a	O
distance	O
.	O
</s>
<s>
Additional	O
game	O
elements	O
not	O
featured	O
in	O
the	O
original	O
Portal	B-Application
include	O
Thermal	O
Discouragement	O
Beams	O
(	O
lasers	O
)	O
,	O
Excursion	O
Funnels	O
(	O
tractor	O
beams	O
)	O
,	O
and	O
Hard	O
Light	O
Bridges	O
,	O
all	O
of	O
which	O
can	O
be	O
transmitted	O
through	O
portals	B-Application
.	O
</s>
<s>
Early	O
demonstrations	O
included	O
Pneumatic	O
Diversity	O
Vents	O
,	O
shown	O
to	O
transport	O
objects	O
and	O
transfer	O
suction	O
power	O
through	O
portals	B-Application
,	O
but	O
these	O
do	O
not	O
appear	O
in	O
the	O
final	O
game	O
.	O
</s>
<s>
The	O
typical	O
objective	O
of	O
a	O
test	O
chamber	O
or	O
level	O
is	O
to	O
use	O
the	O
portal	B-Application
gun	O
and	O
provided	O
gameplay	O
elements	O
to	O
open	O
a	O
locked	O
exit	O
door	O
and	O
progress	O
to	O
the	O
next	O
chamber	O
.	O
</s>
<s>
Paint-like	O
gels	O
(	O
which	O
are	O
dispensed	O
from	O
pipes	O
and	O
can	O
be	O
transported	O
through	O
portals	B-Application
)	O
impart	O
certain	O
properties	O
to	O
surfaces	O
or	O
objects	O
coated	O
with	O
them	O
.	O
</s>
<s>
Players	O
can	O
use	O
orange	O
Propulsion	O
Gel	O
to	O
cross	O
surfaces	O
more	O
quickly	O
,	O
blue	O
Repulsion	O
Gel	O
to	O
bounce	O
from	O
a	O
surface	O
,	O
and	O
white	O
Conversion	O
Gel	O
to	O
allow	O
surfaces	O
to	O
accept	O
portals	B-Application
.	O
</s>
<s>
In	O
the	O
cooperative	O
campaign	O
,	O
two	O
players	O
can	O
use	O
the	O
same	O
console	O
with	O
a	O
split	O
screen	O
,	O
or	O
can	O
use	O
a	O
separate	O
computer	O
or	O
console	O
;	O
Windows	O
,	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
and	O
PlayStation	B-Operating_System
3	I-Operating_System
users	O
can	O
play	O
with	O
each	O
other	O
regardless	O
of	O
platform	O
.	O
</s>
<s>
Both	O
player-characters	O
are	O
robots	O
equipped	O
with	O
independent	O
portal	B-Application
guns	O
,	O
a	O
portal	B-Application
pair	O
placed	O
by	O
either	O
player	O
is	O
usable	O
by	O
both	O
.	O
</s>
<s>
Most	O
chambers	O
lack	O
strict	O
structure	O
,	O
and	O
require	O
players	O
to	O
use	O
both	O
sets	O
of	O
portals	B-Application
for	O
laser	O
or	O
funnel	O
redirection	O
,	O
launches	O
,	O
and	O
other	O
maneuvers	O
.	O
</s>
<s>
Portal	B-Application
2s	I-Application
lead	O
writer	O
Erik	O
Wolpaw	O
estimates	O
each	O
campaign	O
to	O
be	O
about	O
six	O
hours	O
long	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
contains	O
in-game	O
commentary	O
from	O
the	O
game	O
developers	O
,	O
writers	O
,	O
and	O
artists	O
.	O
</s>
<s>
According	O
to	O
Valve	O
,	O
each	O
of	O
the	O
single-player	O
and	O
cooperative	O
campaigns	O
is	O
2	O
to	O
2.5	O
times	O
as	O
long	O
as	O
the	O
campaign	O
in	O
Portal	B-Application
,	O
with	O
the	O
overall	O
game	O
five	O
times	O
as	O
long	O
.	O
</s>
<s>
The	O
Portal	B-Application
series	O
shares	O
a	O
fictional	O
universe	O
with	O
the	O
Half-Life	B-Application
series	O
.	O
</s>
<s>
The	O
events	O
in	O
Portal	B-Application
take	O
place	O
between	O
the	O
first	B-Application
and	O
second	B-Application
Half-Life	B-Application
games	O
,	O
while	O
most	O
of	O
Portal	B-Application
2	I-Application
is	O
set	O
"	O
a	O
long	O
time	O
after	O
"	O
the	O
events	O
in	O
Portal	B-Application
and	O
Half-Life	B-Application
2	I-Application
.	O
</s>
<s>
Before	O
Portal	B-Application
,	O
Aperture	O
Science	O
conducted	O
experiments	O
to	O
determine	O
whether	O
human	O
subjects	O
could	O
safely	O
navigate	O
dangerous	O
"	O
test	O
chambers	O
"	O
,	O
until	O
the	B-Application
artificial	I-Application
intelligence	I-Application
GLaDOS	O
,	O
governing	O
the	O
laboratory	O
,	O
killed	O
its	O
employees	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
the	O
first	B-Application
Portal	B-Application
,	O
the	O
protagonist	O
Chell	O
destroys	O
GLaDOS	O
and	O
momentarily	O
escapes	O
the	O
facility	O
,	O
but	O
is	O
dragged	O
back	O
inside	O
by	O
an	O
unseen	O
figure	O
later	O
identified	O
by	O
writer	O
Erik	O
Wolpaw	O
as	O
the	O
"	O
Party	O
Escort	O
Bot	O
"	O
.	O
</s>
<s>
A	O
promotional	O
comic	O
shows	O
estranged	O
Aperture	O
Science	O
employee	O
Doug	O
Rattmann	O
,	O
who	O
used	O
graffiti	O
to	O
guide	O
the	O
player	O
in	O
Portal	B-Application
,	O
placing	O
Chell	O
into	O
suspended	O
animation	O
to	O
save	O
her	O
life	O
,	O
until	O
the	O
beginning	O
of	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Wheatley	O
(	O
Stephen	O
Merchant	O
)	O
,	O
a	O
personality	O
core	O
,	O
guides	O
her	O
through	O
old	O
test	O
chambers	O
from	O
the	O
first	B-Application
game	O
in	O
an	O
attempt	O
to	O
escape	O
the	O
facility	O
after	O
its	O
reserve	O
power	O
is	O
depleted	O
.	O
</s>
<s>
Wheatley	O
,	O
immediately	O
driven	O
mad	O
with	O
power	O
,	O
installs	O
GLaDOS	O
on	O
a	O
potato	B-Algorithm
battery	I-Algorithm
.	O
</s>
<s>
Chell	O
retrieves	O
the	O
potato	B-Algorithm
battery	I-Algorithm
and	O
they	O
form	O
a	O
reluctant	O
partnership	O
to	O
stop	O
Wheatley	O
before	O
his	O
incompetence	O
destroys	O
the	O
facility	O
.	O
</s>
<s>
In	O
1981	O
,	O
Johnson	O
became	O
mortally	O
ill	O
from	O
moon	O
dust	O
used	O
to	O
manufacture	O
portal-conductive	O
surfaces	O
.	O
</s>
<s>
As	O
the	O
facility	O
crumbles	O
,	O
Chell	O
places	O
a	O
portal	B-Application
on	O
the	O
Moon	O
;	O
she	O
and	O
Wheatley	O
begin	O
to	O
be	O
pulled	O
into	O
the	O
vacuum	O
of	O
space	O
.	O
</s>
<s>
In	O
the	O
first	B-Application
four	O
'	O
sets	O
 '	O
of	O
levels	O
,	O
the	O
robots	O
are	O
sent	O
on	O
ventures	O
into	O
the	O
depths	O
of	O
the	O
Aperture	O
facilities	O
to	O
recover	O
and	O
upload	O
data	O
disks	O
.	O
</s>
<s>
At	O
first	B-Application
,	O
GLaDOS	O
is	O
excited	O
about	O
her	O
non-human	O
test	O
subjects	O
,	O
but	O
later	O
becomes	O
dissatisfied	O
because	O
the	O
two	O
robots	O
cannot	O
truly	O
die	O
,	O
and	O
at	O
one	O
point	O
also	O
gets	O
uncomfortable	O
with	O
their	O
close	O
partnership	O
.	O
</s>
<s>
The	O
saboteur	O
is	O
revealed	O
to	O
be	O
a	O
bird	O
pecking	O
at	O
the	O
console	O
's	O
keyboard	O
,	O
which	O
sends	O
GLaDOS	O
into	O
a	O
panic	O
when	O
she	O
recognizes	O
it	O
as	O
the	O
one	O
who	O
tried	O
to	O
eat	O
her	O
during	O
her	O
time	O
as	O
a	O
potato	B-Algorithm
battery	I-Algorithm
.	O
</s>
<s>
After	O
the	O
success	O
of	O
Portal	B-Application
,	O
Valve	O
decided	O
to	O
make	O
Portal	B-Application
2	I-Application
a	O
standalone	O
product	O
,	O
partly	O
because	O
of	O
pressure	O
from	O
other	O
developers	O
within	O
Valve	O
who	O
wanted	O
to	O
work	O
on	O
a	O
Portal	B-Application
product	O
.	O
</s>
<s>
Work	O
began	O
almost	O
immediately	O
after	O
the	O
release	O
of	O
Portal	B-Application
.	O
</s>
<s>
Valve	O
committed	O
more	O
resources	O
to	O
Portal	B-Application
2s	I-Application
development	O
than	O
they	O
had	O
for	O
the	O
first	B-Application
game	O
;	O
Portal	B-Application
had	O
a	O
team	O
of	O
seven	O
or	O
eight	O
people	O
,	O
but	O
Portal	B-Application
2	I-Application
had	O
a	O
team	O
of	O
30	O
or	O
40	O
.	O
</s>
<s>
According	O
to	O
Erik	O
Wolpaw	O
,	O
some	O
Portal	B-Application
2	I-Application
developers	O
worked	O
on	O
the	O
Left	B-Application
4	I-Application
Dead	I-Application
games	O
to	O
help	O
them	O
meet	O
milestones	O
,	O
but	O
returned	O
to	O
Portal	B-Application
2	I-Application
,	O
"	O
with	O
extra	O
people	O
in	O
tow.	O
"	O
</s>
<s>
Kim	O
Swift	O
,	O
Portals	B-Application
designer	O
,	O
left	O
Valve	O
for	O
Airtight	O
Games	O
halfway	O
through	O
Portal	B-Application
2s	I-Application
development	O
.	O
</s>
<s>
Project	O
manager	O
Erik	O
Johnson	O
said	O
Valve	O
's	O
goal	O
for	O
Portal	B-Application
2	I-Application
was	O
to	O
find	O
a	O
way	O
to	O
"	O
re-surprise	O
"	O
players	O
,	O
which	O
he	O
considered	O
a	O
"	O
pretty	O
terrifying	O
"	O
prospect	O
.	O
</s>
<s>
In	O
March	O
2011	O
,	O
one	O
month	O
before	O
the	O
game	O
's	O
release	O
,	O
Valve	O
president	O
Gabe	O
Newell	O
called	O
Portal	B-Application
2	I-Application
"	O
the	O
best	O
game	O
we	O
've	O
ever	O
done	O
"	O
.	O
</s>
<s>
After	O
Portal	B-Application
2s	I-Application
release	O
,	O
Geoff	O
Keighley	O
wrote	O
that	O
according	O
to	O
Newell	O
,	O
"	O
Portal	B-Application
2	I-Application
will	O
probably	O
be	O
Valve	O
's	O
last	O
game	O
with	O
an	O
isolated	O
single-player	O
experience	O
"	O
.	O
</s>
<s>
Newell	O
said	O
that	O
Valve	O
is	O
not	O
"	O
giving	O
up	O
on	O
single-player	O
"	O
,	O
but	O
intends	O
to	O
include	O
more	O
social	O
features	O
on	O
top	O
of	O
the	O
single	O
player	O
experience	O
,	O
akin	O
to	O
the	O
cooperative	O
mode	O
in	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Initially	O
,	O
Valve	O
planned	O
to	O
exclude	O
portals	B-Application
from	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Valve	O
's	O
F-Stop	O
game	O
was	O
set	O
in	O
the	O
1980s	O
,	O
and	O
would	O
not	O
have	O
featured	O
Chell	O
or	O
GLaDOS	O
;	O
instead	O
,	O
it	O
followed	O
a	O
new	O
test	O
subject	O
involved	O
in	O
a	O
conflict	O
within	O
Aperture	O
after	O
Johnson	O
,	O
in	O
an	O
attempt	O
to	O
reach	O
immortality	O
,	O
uploaded	O
himself	O
into	O
an	O
artificial	B-Application
intelligence	I-Application
and	O
took	O
control	O
of	O
a	O
robot	O
army	O
.	O
</s>
<s>
Though	O
the	O
playtesters	O
liked	O
F-Stop	O
,	O
they	O
expressed	O
disappointment	O
at	O
the	O
omission	O
of	O
portals	B-Application
.	O
</s>
<s>
Valve	O
did	O
not	O
aim	O
to	O
make	O
Portal	B-Application
2	I-Application
more	O
difficult	O
than	O
Portal	B-Application
,	O
but	O
instead	O
to	O
produce	O
"	O
a	O
game	O
where	O
you	O
think	O
your	O
way	O
through	O
particular	O
parts	O
of	O
the	O
level	O
,	O
and	O
feel	O
really	O
smart	O
when	O
you	O
solve	O
it	O
"	O
.	O
</s>
<s>
The	O
developers	O
ran	O
a	O
sanity	B-Error_Name
check	I-Error_Name
before	O
crafting	O
simple	O
levels	O
with	O
the	O
Hammer	B-Application
Editor	I-Application
,	O
Valve	O
's	O
level	O
construction	O
tool	O
.	O
</s>
<s>
Valve	O
aimed	O
to	O
teach	O
new	O
players	O
the	O
portal	B-Application
mechanics	O
while	O
still	O
entertaining	O
experienced	O
players	O
.	O
</s>
<s>
To	O
this	O
end	O
,	O
they	O
streamlined	O
some	O
elements	O
;	O
for	O
example	O
,	O
the	O
moving	O
energy	O
balls	O
of	O
Portal	B-Application
were	O
replaced	O
with	O
lasers	O
,	O
which	O
provide	O
immediate	O
feedback	O
.	O
</s>
<s>
To	O
evoke	O
a	O
sense	O
of	O
nostalgia	O
and	O
time	O
having	O
passed	O
between	O
the	O
games	O
,	O
Valve	O
included	O
test	O
chambers	O
from	O
the	O
original	O
Portal	B-Application
;	O
they	O
used	O
higher-resolution	O
textures	O
supported	O
by	O
the	O
improved	O
game	O
engine	O
,	O
and	O
applied	O
decay	O
,	O
collapse	O
and	O
overgrowth	O
effects	O
.	O
</s>
<s>
The	O
middle	O
section	O
of	O
the	O
single-player	O
campaign	O
takes	O
place	O
in	O
large	O
spaces	O
where	O
few	O
portals	B-Application
can	O
be	O
placed	O
,	O
forcing	O
players	O
to	O
find	O
creative	O
ways	O
to	O
cross	O
.	O
</s>
<s>
The	O
Repulsion	O
(	O
jumping	O
)	O
and	O
Propulsion	O
(	O
running	O
)	O
gels	O
in	O
Portal	B-Application
2	I-Application
originated	O
in	O
Tag	B-Application
:	I-Application
The	I-Application
Power	I-Application
of	I-Application
Paint	I-Application
.	O
</s>
<s>
Valve	O
hired	O
the	O
Tag	O
creators	O
to	O
develop	O
the	O
idea	O
further	O
and	O
later	O
decided	O
to	O
include	O
it	O
in	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Journalists	O
have	O
likened	O
Tag	O
to	O
Narbacular	B-Application
Drop	I-Application
,	O
the	O
DigiPen	O
student	O
project	O
whose	O
mechanics	O
became	O
Portal	B-Application
.	O
</s>
<s>
As	O
the	O
third	O
Tag	O
gel	O
,	O
which	O
allows	O
the	O
character	O
to	O
walk	O
on	O
any	O
surface	O
regardless	O
of	O
gravity	O
,	O
gave	O
playtesters	O
motion	O
sickness	O
,	O
it	O
was	O
replaced	O
by	O
Conversion	O
gel	O
,	O
which	O
integrates	O
with	O
the	O
portal	B-Application
mechanic	O
.	O
</s>
<s>
Rendering	O
techniques	O
developed	O
for	O
Left	B-Application
4	I-Application
Dead	I-Application
2	I-Application
were	O
used	O
to	O
render	O
pools	O
of	O
liquid	O
;	O
Portal	B-Application
2	I-Application
combines	O
"	O
flowing	O
"	O
surface	O
maps	O
to	O
mimic	O
the	O
motion	O
of	O
water	O
with	O
"	O
debris	O
flow	O
"	O
maps	O
and	O
random	O
noise	O
to	O
create	O
realistic	O
,	O
real-time	O
rendering	O
of	O
water	O
effects	O
.	O
</s>
<s>
The	O
cooperative	O
campaign	O
was	O
also	O
inspired	O
by	O
Valve	O
's	O
Left	B-Application
4	I-Application
Dead	I-Application
cooperative	O
games	O
,	O
in	O
which	O
players	O
enjoyed	O
discussing	O
their	O
personal	O
experiences	O
with	O
the	O
game	O
when	O
they	O
had	O
finished	O
playing	O
it	O
.	O
</s>
<s>
While	O
the	O
single	O
player	O
campaign	O
in	O
Portal	B-Application
2	I-Application
is	O
designed	O
to	O
avoid	O
frustrating	O
the	O
player	O
,	O
the	O
cooperative	O
levels	O
focus	O
on	O
coordination	O
and	O
communication	O
,	O
and	O
Valve	O
recognizes	O
they	O
are	O
much	O
more	O
difficult	O
than	O
the	O
single-player	O
puzzles	O
.	O
</s>
<s>
Valve	O
did	O
not	O
include	O
timed	O
puzzles	O
in	O
the	O
single-player	O
campaigns	O
in	O
Portal	B-Application
and	O
Portal	B-Application
2	I-Application
,	O
but	O
found	O
that	O
their	O
inclusion	O
in	O
the	O
cooperative	O
mode	O
is	O
effective	O
and	O
gives	O
players	O
a	O
positive	O
feeling	O
after	O
they	O
successfully	O
plan	O
and	O
execute	O
difficult	O
maneuvers	O
.	O
</s>
<s>
As	O
soon	O
as	O
a	O
playtester	O
discovered	O
a	O
way	O
to	O
complete	O
a	O
puzzle	O
with	O
one	O
set	O
of	O
portals	B-Application
,	O
the	O
level	O
was	O
sent	O
back	O
to	O
the	O
designers	O
for	O
further	O
work	O
.	O
</s>
<s>
Some	O
of	O
the	O
puzzle	O
chambers	O
were	O
designed	O
asymmetrically	O
;	O
one	O
player	O
would	O
manipulate	O
portals	B-Application
and	O
controls	O
to	O
allow	O
the	O
other	O
player	O
to	O
cross	O
the	O
room	O
,	O
emphasizing	O
that	O
the	O
two	O
characters	O
,	O
while	O
working	O
together	O
,	O
are	O
separate	O
entities	O
.	O
</s>
<s>
According	O
to	O
Wolpaw	O
,	O
the	O
mode	O
was	O
similar	O
to	O
the	O
video	O
game	O
Speedball	B-Application
;	O
one	O
team	O
would	O
try	O
to	O
transport	O
a	O
ball	O
from	O
one	O
side	O
of	O
the	O
playing	O
field	O
to	O
the	O
other	O
using	O
portals	B-Application
,	O
while	O
the	O
other	O
team	O
would	O
attempt	O
to	O
stop	O
them	O
with	O
their	O
own	O
use	O
of	O
portals	B-Application
.	O
</s>
<s>
Valve	O
realized	O
that	O
people	O
enjoyed	O
solving	O
puzzles	O
with	O
portals	B-Application
more	O
and	O
therefore	O
they	O
focused	O
on	O
the	O
cooperative	O
mode	O
.	O
</s>
<s>
Wolpaw	O
and	O
ex-National	O
Lampoon	O
writer	O
Jay	O
Pinkerton	O
wrote	O
the	O
single-player	O
story	O
,	O
while	O
Left	B-Application
4	I-Application
Dead	I-Application
writer	O
Chet	O
Faliszek	O
wrote	O
GLaDOS	O
's	O
lines	O
for	O
the	O
cooperative	O
campaign	O
.	O
</s>
<s>
They	O
considered	O
expanding	O
the	O
"	O
sterility	O
and	O
dryness	O
"	O
of	O
Portal	B-Application
and	O
adding	O
more	O
comedy	O
to	O
the	O
script	O
.	O
</s>
<s>
In	O
June	O
2008	O
,	O
based	O
on	O
information	O
from	O
a	O
casting	O
call	O
website	O
and	O
leaked	O
script	O
samples	O
,	O
Kotaku	O
reported	O
that	O
Valve	O
was	O
seeking	O
voice	O
actors	O
to	O
play	O
Johnson	O
,	O
named	O
him	O
as	O
an	O
AI	B-Application
and	O
identified	O
the	O
game	O
as	O
a	O
prequel	O
.	O
</s>
<s>
Following	O
negative	O
playtester	O
feedback	O
about	O
the	O
omission	O
of	O
Chell	O
and	O
GLaDOS	O
,	O
Portal	B-Application
2	I-Application
was	O
re-conceived	O
as	O
a	O
sequel	O
.	O
</s>
<s>
One	O
of	O
these	O
joke	O
endings	O
was	O
triggered	O
by	O
shooting	O
a	O
portal	B-Application
onto	O
the	O
moon	O
's	O
surface	O
,	O
after	O
which	O
the	O
player	O
's	O
character	O
would	O
die	O
from	O
asphyxiation	O
over	O
a	O
closing	O
song	O
,	O
but	O
the	O
idea	O
of	O
creating	O
a	O
portal	B-Application
on	O
the	O
moon	O
was	O
incorporated	O
into	O
the	O
game	O
's	O
final	O
ending	O
.	O
</s>
<s>
The	O
cooperative	O
campaign	O
was	O
planned	O
to	O
feature	O
a	O
more	O
detailed	O
storyline	O
,	O
in	O
which	O
GLaDOS	O
would	O
send	O
two	O
robots	O
to	O
discover	O
human	O
artifacts	O
,	O
such	O
as	O
a	O
comic	O
based	O
on	O
a	O
pastiche	O
of	O
Garfield	B-Application
.	O
</s>
<s>
Wolpaw	O
said	O
that	O
while	O
many	O
story	O
elements	O
of	O
Portal	B-Application
are	O
revisited	O
in	O
Portal	B-Application
2	I-Application
,	O
he	O
avoided	O
some	O
of	O
the	O
memes	O
—	O
such	O
as	O
the	O
frequently	O
repeated	O
"	O
the	B-Application
cake	I-Application
is	I-Application
a	I-Application
lie	I-Application
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
produced	O
its	O
own	O
memes	O
,	O
including	O
a	O
space-obsessed	O
personality	O
core	O
.	O
</s>
<s>
Valve	O
later	O
created	O
a	O
Space	O
Core	O
modification	O
for	O
the	O
game	O
The	B-Application
Elder	I-Application
Scrolls	I-Application
V	I-Application
:	I-Application
Skyrim	I-Application
(	O
see	O
below	O
)	O
,	O
and	O
the	O
Space	O
Core	O
also	O
appeared	O
as	O
a	O
laser-based	O
engraving	O
on	O
a	O
panel	O
manufactured	O
by	O
NASA	O
for	O
the	O
International	O
Space	O
Station	O
.	O
</s>
<s>
Richard	O
McCormick	O
of	O
PlayStation	B-Operating_System
3	I-Operating_System
Magazine	O
identified	O
several	O
elements	O
of	O
Portal	B-Application
2s	I-Application
story	O
that	O
reference	O
the	O
myth	O
of	O
Prometheus	B-Language
;	O
McCormick	O
wrote	O
that	O
GLaDOS	O
is	O
a	O
personification	O
of	O
Prometheus	B-Language
,	O
who	O
grants	O
knowledge	O
to	O
humanity	O
—	O
in	O
the	O
form	O
of	O
the	O
portal	B-Application
gun	O
—	O
and	O
is	O
then	O
punished	O
by	O
being	O
bound	O
to	O
a	O
rock	O
,	O
pecked	O
at	O
by	O
birds	O
,	O
and	O
is	O
cast	O
into	O
the	O
pits	O
of	O
Tartarus	O
.	O
</s>
<s>
McCormick	O
also	O
likens	O
Wheatley	O
to	O
Prometheus	B-Language
 '	O
foolish	O
brother	O
Epimetheus	O
.	O
</s>
<s>
Within	O
the	O
game	O
,	O
a	O
turret	O
makes	O
reference	O
to	O
the	O
Prometheus	B-Language
myth	O
,	O
the	O
word	O
"	O
Tartarus	O
"	O
is	O
visible	O
on	O
the	O
supporting	O
columns	O
in	O
the	O
depths	O
of	O
Aperture	O
Science	O
,	O
and	O
a	O
portrait	O
of	O
Cave	O
and	O
Caroline	O
also	O
shows	O
Aeschylus	O
,	O
the	O
presumed	O
author	O
of	O
Prometheus	B-Language
Bound	O
.	O
</s>
<s>
Journalists	O
and	O
players	O
have	O
also	O
found	O
connections	O
between	O
Portal	B-Application
2	I-Application
and	O
Half-Life	B-Application
2	I-Application
.	O
</s>
<s>
As	O
an	O
easter	O
egg	O
,	O
a	O
hidden	O
area	O
in	O
Portal	B-Application
2	I-Application
contains	O
the	O
empty	O
dry	O
dock	O
of	O
Aperture	O
Science	O
's	O
cargo	O
ship	O
,	O
the	O
Borealis	O
,	O
which	O
is	O
found	O
during	O
Half-Life	B-Application
2	I-Application
:	I-Application
Episode	I-Application
Two	I-Application
to	O
have	O
been	O
stranded	O
in	O
the	O
Arctic	O
as	O
a	O
result	O
of	O
a	O
teleportation	O
experiment	O
.	O
</s>
<s>
Though	O
Portal	B-Application
2	I-Application
introduced	O
some	O
new	O
characters	O
,	O
the	O
writers	O
wanted	O
to	O
maintain	O
the	O
one-on-one	O
relationships	O
between	O
each	O
character	O
and	O
the	O
player-character	O
.	O
</s>
<s>
Valve	O
explored	O
the	O
possibility	O
of	O
introducing	O
a	O
new	O
protagonist	O
for	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
The	O
playtesters	O
accepted	O
playing	O
as	O
a	O
different	O
character	O
for	O
the	O
first	B-Application
part	O
of	O
the	O
game	O
,	O
but	O
they	O
became	O
disoriented	O
when	O
GLaDOS	O
did	O
not	O
recognize	O
them	O
.	O
</s>
<s>
The	O
writers	O
returned	O
to	O
using	O
Chell	O
,	O
the	O
protagonist	O
of	O
Portal	B-Application
.	O
</s>
<s>
They	O
returned	O
to	O
the	O
orange	O
"	O
dehumanizing	O
"	O
jumpsuit	O
from	O
Portal	B-Application
with	O
the	O
top	O
tied	O
around	O
Chell	O
's	O
waist	O
to	O
enhance	O
her	O
freedom	O
of	O
movement	O
and	O
help	O
her	O
"	O
stand	O
out	O
more	O
as	O
an	O
individual	O
"	O
.	O
</s>
<s>
As	O
in	O
the	O
first	B-Application
game	O
,	O
Chell	O
's	O
facial	O
appearance	O
is	O
based	O
on	O
that	O
of	O
voice	O
actress	O
Alésia	O
Glidewell	O
.	O
</s>
<s>
As	O
part	O
of	O
her	O
character	O
arc	O
,	O
the	O
plot	O
moves	O
GLaDOS	O
from	O
her	O
anger	O
with	O
Chell	O
for	O
her	O
actions	O
in	O
Portal	B-Application
,	O
which	O
Wolpaw	O
said	O
"	O
was	O
going	O
to	O
get	O
old	O
pretty	O
quick	O
"	O
,	O
to	O
an	O
internal	O
struggle	O
.	O
</s>
<s>
Pictures	O
of	O
Cave	O
Johnson	O
,	O
based	O
on	O
the	O
face	O
of	O
lead	O
animator	O
Bill	O
Fletcher	O
,	O
appear	O
throughout	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Though	O
comparisons	O
have	O
been	O
made	O
between	O
Johnson	O
and	O
Andrew	O
Ryan	O
,	O
the	O
wealthy	O
industrialist	O
who	O
created	O
the	O
fictional	O
underwater	O
city	O
of	O
Rapture	O
in	O
BioShock	B-Application
,	O
Wolpaw	O
says	O
the	O
writers	O
did	O
not	O
consider	O
this	O
character	O
while	O
creating	O
Johnson	O
.	O
</s>
<s>
GLaDOS	O
returns	O
from	O
Portal	B-Application
as	O
a	O
major	O
character	O
and	O
the	O
game	O
's	O
antagonist	O
,	O
and	O
is	O
voiced	O
by	O
Ellen	O
McLain	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
contains	O
both	O
scored	O
and	O
procedurally	O
generated	O
music	O
created	O
by	O
Valve	O
's	O
composer	O
,	O
Mike	O
Morasky	O
,	O
and	O
two	O
songs	O
;	O
"	O
Want	O
You	O
Gone	O
"	O
recorded	O
by	O
Jonathan	O
Coulton	O
,	O
used	O
on	O
the	O
final	O
credits	O
of	O
the	O
single-player	O
mode	O
,	O
and	O
"	O
Exile	O
Vilify	O
"	O
by	O
the	O
National	O
,	O
used	O
in	O
the	O
background	O
of	O
one	O
of	O
the	O
Rat	O
Man	O
's	O
dens	O
.	O
</s>
<s>
The	O
full	O
soundtrack	O
"	O
Songs	O
to	O
Test	O
By	O
"	O
,	O
containing	O
most	O
of	O
the	O
songs	O
in	O
the	O
game	O
,	O
was	O
released	O
as	O
three	O
free	O
downloads	O
between	O
May	O
and	O
September	O
2011	O
,	O
and	O
later	O
in	O
October	O
2012	O
as	O
a	O
retail	O
Collector	O
's	O
Edition	O
,	O
including	O
the	O
soundtrack	O
from	O
Portal	B-Application
.	O
</s>
<s>
In	O
January	O
2008	O
,	O
Valve	O
spokesman	O
Doug	O
Lombardi	O
told	O
Eurogamer	O
,	O
"	O
There	O
'll	O
be	O
more	O
Portal	B-Application
,	O
for	O
sure	O
"	O
,	O
and	O
Portal	B-Application
designer	O
Kim	O
Swift	O
confirmed	O
that	O
work	O
on	O
Portal	B-Application
2	I-Application
would	O
begin	O
the	O
following	O
month	O
.	O
</s>
<s>
Swift	O
said	O
that	O
a	O
multiplayer	O
mode	O
in	O
Portal	B-Application
was	O
"	O
technically	O
possible	O
"	O
,	O
but	O
that	O
it	O
was	O
"	O
less	O
fun	O
than	O
you	O
'd	O
think.	O
"	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
officially	O
announced	O
on	O
March	O
5	O
,	O
2010	O
,	O
via	O
Game	O
Informer	O
.	O
</s>
<s>
On	O
March	O
1	O
,	O
Valve	O
released	O
a	O
patch	O
for	O
Portal	B-Application
that	O
included	O
a	O
new	O
achievement	O
,	O
"	O
Transmission	O
Received	O
"	O
,	O
requiring	O
the	O
player	O
to	O
manipulate	O
in-game	O
radios	O
.	O
</s>
<s>
The	O
images	O
included	O
hints	O
to	O
a	O
BBS	B-Application
phone	O
number	O
that	O
,	O
when	O
accessed	O
,	O
provided	O
a	O
large	O
number	O
of	O
ASCII-based	O
images	O
relating	O
to	O
Portal	B-Application
and	O
segments	O
of	O
Aperture	O
Science	O
documents	O
.	O
</s>
<s>
Many	O
of	O
these	O
ASCII	B-Protocol
pictures	O
were	O
later	O
published	O
in	O
the	O
Game	O
Informer	O
reveal	O
of	O
the	O
title	O
.	O
</s>
<s>
New	O
ASCII	B-Protocol
images	O
continued	O
to	O
appear	O
on	O
the	O
BBS	B-Application
after	O
the	O
official	O
announcement	O
.	O
</s>
<s>
Background	O
on	O
the	O
ARG	O
is	O
embedded	O
in	O
additional	O
SSTV	O
images	O
found	O
in	O
a	O
hidden	O
room	O
in	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Valve	O
's	O
Adam	O
Foster	O
came	O
up	O
with	O
the	O
idea	O
for	O
the	O
ARG	O
,	O
tying	O
it	O
to	O
the	O
Game	O
Informer	O
reveal	O
,	O
and	O
he	O
provided	O
his	O
own	O
home	O
phone	O
line	O
to	O
run	O
the	O
BBS	B-Application
software	O
on	O
,	O
as	O
Valve	O
's	O
offices	O
at	O
the	O
time	O
were	O
too	O
modern	O
to	O
support	O
the	O
protocol	O
.	O
</s>
<s>
A	O
second	B-Application
Portal	B-Application
patch	O
released	O
on	O
March	O
3	O
altered	O
the	O
game	O
's	O
ending	O
sequence	O
to	O
show	O
Chell	O
being	O
pulled	O
back	O
into	O
the	O
Aperture	O
facility	O
.	O
</s>
<s>
Gaming	O
journalists	O
speculated	O
that	O
an	O
announcement	O
of	O
Portal	B-Application
2	I-Application
was	O
imminent	O
.	O
</s>
<s>
On	O
March	O
5	O
,	O
Game	O
Informer	O
announced	O
Portal	B-Application
2s	I-Application
official	O
release	O
on	O
the	O
cover	O
of	O
its	O
April	O
issue	O
.	O
</s>
<s>
During	O
the	O
following	O
week	O
,	O
Gabe	O
Newell	O
's	O
speech	O
accepting	O
the	O
Pioneer	O
Award	O
at	O
the	O
Game	O
Developers	O
Conference	O
2010	O
ended	O
with	O
a	O
fake	O
blue	O
screen	O
of	O
death	O
appearing	O
on	O
a	O
screen	O
behind	O
him	O
with	O
a	O
message	O
purported	O
to	O
be	O
from	O
GLaDOS	O
which	O
hinted	O
of	O
further	O
Portal	B-Application
2	I-Application
news	O
at	O
the	O
upcoming	O
E3	O
2010	O
.	O
</s>
<s>
Two	O
weeks	O
before	O
the	O
E3	O
,	O
game	O
journalists	O
received	O
a	O
cryptic	O
e-mail	O
,	O
worded	O
as	O
a	O
press	O
release	O
from	O
Aperture	O
Science	O
,	O
hinting	O
that	O
the	O
presentation	O
on	O
Portal	B-Application
2	I-Application
would	O
be	O
replaced	O
with	O
"	O
a	O
surprise	O
"	O
jointly	O
hosted	O
by	O
Aperture	O
Science	O
and	O
Valve	O
.	O
</s>
<s>
This	O
prompted	O
speculation	O
that	O
the	O
surprise	O
would	O
be	O
the	O
announcement	O
of	O
Half-Life	B-Application
2	I-Application
:	I-Application
Episode	I-Application
Three	I-Application
,	O
but	O
Valve	O
confirmed	O
that	O
it	O
would	O
be	O
about	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
The	O
surprise	O
was	O
the	O
announcement	O
of	O
Portal	B-Application
2	I-Application
on	O
PlayStation	B-Operating_System
3	I-Operating_System
.	O
</s>
<s>
The	O
March	O
2010	O
announcement	O
said	O
that	O
Portal	B-Application
2	I-Application
would	O
be	O
released	O
in	O
late	O
2010	O
.	O
</s>
<s>
In	O
August	O
2010	O
,	O
Valve	O
postponed	O
the	O
release	O
to	O
February	O
2011	O
,	O
with	O
a	O
Steam	B-Application
release	O
date	O
of	O
February	O
9	O
,	O
to	O
allow	O
it	O
to	O
complete	O
changes	O
to	O
the	O
game	O
's	O
dialogue	O
,	O
to	O
fill	O
and	O
connect	O
about	O
sixty	O
test	O
chambers	O
,	O
and	O
to	O
finish	O
refinements	O
to	O
the	O
gel	O
gameplay	O
mechanic	O
.	O
</s>
<s>
On	O
February	O
18	O
,	O
2011	O
,	O
Newell	O
confirmed	O
that	O
Valve	O
had	O
completed	O
the	O
development	O
work	O
on	O
Portal	B-Application
2	I-Application
and	O
that	O
they	O
were	O
"	O
waiting	O
for	O
final	O
approvals	O
and	O
to	O
get	O
the	O
discs	O
manufactured	O
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
the	O
first	B-Application
Valve	O
product	O
simultaneously	O
released	O
for	O
Windows	O
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
computers	O
through	O
the	O
Steam	B-Application
platform	O
.	O
</s>
<s>
On	O
April	O
1	O
,	O
2011	O
,	O
Valve	O
released	O
another	O
alternate	O
reality	O
game	O
called	O
the	B-Application
Potato	I-Application
Sack	I-Application
.	O
</s>
<s>
Some	O
journalists	O
believed	O
the	O
game	O
denoted	O
the	O
release	O
of	O
Portal	B-Application
2	I-Application
on	O
April	O
15	O
,	O
2011	O
,	O
instead	O
of	O
the	O
target	O
release	O
date	O
of	O
April	O
19	O
,	O
2011	O
.	O
</s>
<s>
On	O
April	O
15	O
,	O
the	O
players	O
discovered	O
"	O
GLaDOS	O
@Home	O
"	O
,	O
a	O
distributed	B-Architecture
computing	I-Architecture
spoof	O
that	O
encouraged	O
participants	O
to	O
play	O
the	O
games	O
to	O
unlock	O
Portal	B-Application
2	I-Application
early	O
.	O
</s>
<s>
Once	O
the	O
puzzles	O
were	O
solved	O
,	O
Portal	B-Application
2	I-Application
was	O
unlocked	O
on	O
April	O
18	O
at	O
around	O
21:30	O
PST	O
,	O
roughly	O
ten	O
hours	O
before	O
its	O
planned	O
release	O
at	O
7:00	O
PST	O
on	O
the	O
next	O
day	O
.	O
</s>
<s>
Valve	O
created	O
a	O
series	O
of	O
television	O
commercials	O
to	O
promote	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Valve	O
also	O
developed	O
online	O
promotional	O
videos	O
featuring	O
J	O
.	O
K	O
.	O
Simmons	O
narrating	O
as	O
Cave	O
Johnson	O
,	O
to	O
promote	O
new	O
elements	O
of	O
Portal	B-Application
2s	I-Application
gameplay	O
.	O
</s>
<s>
These	O
videos	O
were	O
part	O
of	O
a	O
larger	O
effort	O
described	O
by	O
Newell	O
as	O
a	O
"	O
documentary-style	O
investment	O
opportunity	O
"	O
for	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
An	O
earlier	O
video	O
released	O
on	O
February	O
14	O
,	O
2011	O
,	O
promoted	O
the	O
cooperative	O
aspect	O
of	O
Portal	B-Application
2	I-Application
as	O
a	O
St.	O
Valentine	O
's	O
gift	O
and	O
"	O
lit	O
up	O
our	O
preorders	O
,	O
our	O
buzz	O
,	O
all	O
the	O
metrics	O
that	O
are	O
used	O
and	O
collected	O
by	O
publishers	O
and	O
retailers	O
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
includes	O
bonus	O
content	O
,	O
including	O
four	O
promotional	O
videos	O
,	O
a	O
Lab	O
Rat	O
comic	O
,	O
and	O
an	O
interactive	O
trailer	O
for	O
the	O
2011	O
film	O
Super	O
8	O
,	O
constructed	O
with	O
the	O
Source	B-Application
game	I-Application
engine	I-Application
.	O
</s>
<s>
Valve	O
planned	O
to	O
produce	O
downloadable	B-Protocol
content	I-Protocol
for	O
Portal	B-Application
2	I-Application
,	O
beginning	O
with	O
"	O
Peer	O
Review	O
"	O
,	O
released	O
on	O
October	O
4	O
,	O
2011	O
.	O
</s>
<s>
The	O
content	O
also	O
adds	O
a	O
"	O
challenge	O
mode	O
"	O
similar	O
to	O
that	O
in	O
Portal	B-Application
—	O
players	O
try	O
to	O
complete	O
specific	O
chambers	O
with	O
the	O
shortest	O
time	O
or	O
fewest	O
portals	B-Application
used	O
,	O
both	O
which	O
are	O
tracked	O
on	O
overall	O
and	O
friends	O
leaderboards	O
.	O
</s>
<s>
According	O
to	O
Faliszek	O
,	O
user-generated	O
content	O
for	O
Portal	B-Application
2	I-Application
would	O
be	O
available	O
on	O
all	O
platforms	O
,	O
but	O
because	O
of	O
software	O
dependencies	O
,	O
the	O
necessary	O
modding	O
tools	O
would	O
only	O
be	O
available	O
for	O
Windows	O
.	O
</s>
<s>
Valve	O
released	O
beta	O
versions	O
of	O
the	O
modding	O
tools	O
on	O
May	O
10	O
,	O
2011	O
,	O
and	O
supported	O
a	O
competition	O
held	O
by	O
the	O
community	O
mapping	O
website	O
"	O
Thinking	O
with	O
Portals	B-Application
"	O
in	O
May	O
2011	O
,	O
providing	O
prizes	O
for	O
the	O
most-selected	O
maps	O
.	O
</s>
<s>
The	O
"	O
Perpetual	O
Testing	O
Initiative	O
"	O
,	O
a	O
free	O
title	O
update	O
for	O
the	O
Windows	O
and	O
Mac	O
versions	O
,	O
was	O
released	O
on	O
May	O
8	O
,	O
2012	O
,	O
and	O
includes	O
a	O
new	O
level	O
editor	O
and	O
a	O
means	O
of	O
obtaining	O
and	O
sharing	O
user-created	O
levels	O
through	O
the	O
Steam	B-Application
Workshop	O
.	O
</s>
<s>
In	O
November	O
2011	O
,	O
GTTV	O
host	O
Geoff	O
Keighley	O
said	O
that	O
Valve	O
was	O
developing	O
a	O
simplified	O
level	O
editing	O
tool	O
to	O
allow	O
novice	O
editors	O
to	O
assemble	O
test	O
chambers	O
without	O
learning	O
how	O
to	O
use	O
the	O
modified	O
Valve	B-Application
Hammer	I-Application
Editor	I-Application
,	O
and	O
an	O
in-game	O
system	O
to	O
distribute	O
user-created	O
levels	O
via	O
the	O
Steam	B-Application
Workshop	O
.	O
</s>
<s>
Within	O
a	O
few	O
days	O
of	O
release	O
,	O
the	O
Perpetual	O
Testing	O
Initiative	O
add-on	O
had	O
been	O
used	O
to	O
create	O
35,000	O
maps	O
,	O
with	O
1.3	O
million	O
downloads	O
of	O
these	O
maps	O
through	O
Steam	B-Application
.	O
</s>
<s>
The	O
first	B-Application
release	O
of	O
the	O
Perpetual	O
Testing	O
Initiative	O
was	O
limited	O
to	O
single-player	O
maps	O
,	O
but	O
a	O
patch	O
released	O
in	O
August	O
2012	O
enabled	O
users	O
to	O
create	O
new	O
levels	O
for	O
cooperative	O
play	O
.	O
</s>
<s>
,	O
Valve	O
supports	O
fan	O
reuse	O
of	O
Portal	B-Application
2	I-Application
content	O
,	O
offering	O
selected	O
assets	O
and	O
assistance	O
.	O
</s>
<s>
The	O
Windows	O
release	O
of	O
Bastion	B-Application
includes	O
a	O
weapon	O
inspired	O
by	O
Portal	B-Application
2s	I-Application
Conversion	O
Gel	O
and	O
turrets	O
;	O
its	O
developer	O
Supergiant	O
Games	O
received	O
writing	O
assistance	O
from	O
Erik	O
Wolpaw	O
and	O
McLain	O
voiced	O
new	O
lines	O
for	O
the	O
turrets	O
.	O
</s>
<s>
An	O
add-on	O
scenario	O
for	O
Hidden	O
Path	O
Entertainment	O
's	O
tower	B-Application
defense	I-Application
game	I-Application
Defense	B-Application
Grid	I-Application
:	I-Application
The	I-Application
Awakening	I-Application
incorporates	O
GLaDOS	O
as	O
an	O
antagonist	O
using	O
new	O
dialogue	O
from	O
McLain	O
and	O
assets	O
from	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
For	O
a	O
patch	O
for	O
Bethesda	O
's	O
The	B-Application
Elder	I-Application
Scrolls	I-Application
V	I-Application
:	I-Application
Skyrim	I-Application
that	O
incorporated	O
support	O
for	O
Steam	B-Application
Workshop	O
content	O
,	O
Valve	O
developed	O
a	O
free	O
add-on	O
module	O
that	O
introduced	O
the	O
Space	O
Core	O
as	O
a	O
non-player	O
character	O
that	O
follows	O
the	O
player	O
around	O
.	O
</s>
<s>
Valve	O
collaborated	O
with	O
Zen	O
Studios	O
to	O
create	O
a	O
Portal	O
2-themed	O
pinball	O
table	O
,	O
among	O
other	O
Valve-themed	O
tables	O
,	O
for	O
their	O
games	O
Pinball	B-Application
FX	I-Application
2	I-Application
and	O
Zen	B-Application
Pinball	I-Application
.	O
</s>
<s>
A	O
Portal	O
2-themed	O
set	O
is	O
available	O
for	O
Lego	B-Application
Dimensions	I-Application
by	O
Warner	O
Bros	O
.	O
Entertainment	O
and	O
Traveller	O
's	O
Tales	O
;	O
the	O
game	O
features	O
additional	O
stories	O
written	O
by	O
Traveller	O
's	O
Tales	O
with	O
Valve	O
's	O
blessing	O
set	O
after	O
the	O
events	O
of	O
Portal	B-Application
2	I-Application
,	O
with	O
Ellen	O
McLain	O
,	O
Stephen	O
Merchant	O
and	O
J.K.	O
Simmons	O
reprising	O
their	O
respective	O
voice	O
roles	O
,	O
as	O
well	O
as	O
a	O
new	O
GLaDOS	O
credits	O
song	O
written	O
by	O
Jonathan	O
Coulton	O
and	O
performed	O
by	O
McLain	O
.	O
</s>
<s>
The	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
version	O
was	O
added	O
to	O
the	O
backwards	O
compatibility	O
feature	O
for	O
the	B-Device
Xbox	I-Device
One	I-Device
in	O
June	O
2016	O
.	O
</s>
<s>
Alongside	O
Portal	B-Application
,	O
Portal	B-Application
2	I-Application
was	O
released	O
on	O
the	O
Nintendo	B-Application
Switch	I-Application
on	O
June	O
28	O
,	O
2022	O
,	O
as	O
part	O
of	O
Portal	B-Application
:	O
Companion	O
Collection	O
,	O
developed	O
by	O
Valve	O
and	O
Nvidia	O
Lightspeed	O
Studios	O
.	O
</s>
<s>
Valve	O
announced	O
"	O
Teach	O
with	O
Portals	B-Application
"	O
and	O
"	O
Steam	B-Application
for	O
Schools	O
"	O
in	O
June	O
2012	O
,	O
initiatives	O
that	O
offered	O
Portal	B-Application
2	I-Application
and	O
Portal	B-Application
2	I-Application
Puzzle	O
Maker	O
for	O
education	O
.	O
</s>
<s>
The	O
educational	O
version	O
was	O
free	O
but	O
only	O
contained	O
the	O
single-player	O
campaign	O
and	O
Puzzle	O
Maker	O
,	O
and	O
was	O
only	O
available	O
for	O
"	O
Steam	B-Application
for	O
Schools	O
"	O
users	O
.	O
</s>
<s>
Several	O
critics	O
wrote	O
that	O
Portal	B-Application
2	I-Application
excels	O
in	O
teaching	O
the	O
player	O
to	O
solve	O
puzzles	O
;	O
in	O
a	O
review	O
for	O
the	O
New	O
York	O
Times	O
,	O
Seth	O
Schiesel	O
wrote	O
,	O
"	O
Somewhere	O
out	O
there	O
an	O
innovative	O
,	O
dynamic	O
high	O
school	O
physics	O
teacher	O
will	O
use	O
Portal	B-Application
2	I-Application
as	O
the	O
linchpin	O
of	O
an	O
entire	O
series	O
of	O
lessons	O
and	O
will	O
immediately	O
become	O
the	O
most	O
important	O
science	O
teacher	O
those	O
lucky	O
students	O
have	O
ever	O
had.	O
"	O
</s>
<s>
Mathematics	O
and	O
science	O
teachers	O
wrote	O
e-mails	O
to	O
Valve	O
to	O
tell	O
them	O
how	O
they	O
had	O
included	O
Portal	B-Application
in	O
their	O
classroom	O
lessons	O
as	O
part	O
of	O
a	O
project	O
to	O
promote	O
the	O
"	O
gamification	O
of	O
learning	O
"	O
.	O
</s>
<s>
Portal	B-Application
developers	O
Joshua	O
Weier	O
and	O
Yasser	O
Malaika	O
led	O
a	O
team	O
within	O
Valve	O
to	O
explore	O
ways	O
of	O
using	O
Portal	B-Application
2	I-Application
for	O
education	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
development	O
of	O
Puzzle	O
Maker	O
,	O
a	O
level	O
editor	O
for	O
Portal	B-Application
2	I-Application
players	O
,	O
built	O
from	O
the	O
professional	O
tools	O
used	O
to	O
develop	O
the	O
game	O
.	O
</s>
<s>
This	O
formed	O
the	O
basis	O
of	O
a	O
new	O
"	O
Steam	B-Application
for	O
Schools	O
"	O
initiative	O
launched	O
in	O
June	O
2012	O
,	O
under	O
which	O
educators	O
could	O
acquire	O
Portal	B-Application
2	I-Application
and	O
the	O
Puzzle	O
Maker	O
software	O
free	O
of	O
charge	O
for	O
classroom	O
use	O
through	O
its	O
"	O
Teach	O
with	O
Portals	B-Application
"	O
program	O
.	O
</s>
<s>
In	O
November	O
2012	O
,	O
Valve	O
estimated	O
that	O
over	O
2,500	O
educators	O
were	O
using	O
the	O
"	O
Teach	O
with	O
Portals	B-Application
"	O
software	O
within	O
their	O
lesson	O
plans	O
.	O
</s>
<s>
In	O
2016	O
,	O
a	O
study	O
demonstrated	O
that	O
the	O
Portal	B-Application
2	I-Application
Puzzle	O
Maker	O
can	O
be	O
used	O
as	O
a	O
measure	O
of	O
fluid	O
intelligence	O
,	O
similar	O
to	O
the	O
(	O
BOMAT	O
)	O
.	O
</s>
<s>
Referred	O
to	O
as	O
the	O
Portal	B-Application
2	I-Application
Test	O
Battery	O
,	O
the	O
participants	O
of	O
the	O
study	O
completed	O
a	O
series	O
of	O
test	O
chambers	O
that	O
progressively	O
became	O
harder	O
.	O
</s>
<s>
Through	O
multiple	O
pretests	O
and	O
post	O
tests	O
,	O
a	O
2014	O
study	O
has	O
shown	O
that	O
Portal	B-Application
2	I-Application
can	O
improve	O
problem	O
solving	O
skills	O
,	O
spatial	O
skills	O
,	O
and	O
persistence	O
for	O
a	O
designated	O
task	O
.	O
</s>
<s>
Another	O
study	O
done	O
in	O
2017	O
found	O
that	O
commercial	O
video	O
games	O
,	O
like	O
Portal	B-Application
2	I-Application
,	O
can	O
also	O
increase	O
communication	O
,	O
adaptability	O
and	O
resourcefulness	O
.	O
</s>
<s>
Sixense	B-Device
developed	O
a	O
version	O
of	O
Portal	B-Application
2	I-Application
to	O
support	O
the	O
Razer	B-Device
Hydra	I-Device
motion	B-Device
controller	I-Device
for	O
PC	B-Device
that	O
allows	O
enhanced	O
control	O
of	O
some	O
game	O
elements	O
.	O
</s>
<s>
Ten	O
extra	O
single-player	O
levels	O
are	O
available	O
as	O
downloadable	B-Protocol
content	I-Protocol
for	O
this	O
version	O
.	O
</s>
<s>
Writer	O
Chet	O
Faliszek	O
said	O
Sixense	B-Device
developers	O
spent	O
nine	O
months	O
to	O
a	O
year	O
in-house	O
at	O
Valve	O
preparing	O
the	O
native	O
version	O
.	O
</s>
<s>
A	O
limited	O
edition	O
of	O
the	O
Razer	B-Device
Hydra	I-Device
comes	O
bundled	O
with	O
a	O
copy	O
of	O
Portal	B-Application
2	I-Application
for	O
PC	B-Device
.	O
</s>
<s>
The	O
announcement	O
that	O
Portal	B-Application
2	I-Application
would	O
be	O
available	O
on	O
PlayStation	B-Operating_System
3	I-Operating_System
came	O
as	O
a	O
surprise	O
to	O
the	O
industry	O
because	O
Gabe	O
Newell	O
had	O
criticized	O
that	O
console	O
in	O
the	O
past	O
,	O
citing	O
difficulties	O
in	O
the	O
port	O
of	O
The	O
Orange	O
Box	O
.	O
</s>
<s>
The	O
move	O
toward	O
the	O
PlayStation	B-Operating_System
3	I-Operating_System
was	O
a	O
result	O
of	O
growing	O
frustration	O
with	O
Microsoft	O
's	O
policies	O
for	O
Xbox	B-Operating_System
360	I-Operating_System
content	O
,	O
including	O
the	O
difficulty	O
of	O
releasing	O
patches	O
and	O
new	O
content	O
.	O
</s>
<s>
Newell	O
saw	O
Sony	O
's	O
publication	O
model	O
as	O
more	O
open	O
,	O
allowing	O
Steam-like	O
features	O
to	O
be	O
used	O
on	O
the	O
console	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
the	O
first	B-Application
PlayStation	B-Operating_System
3	I-Operating_System
game	O
to	O
support	O
a	O
subset	O
of	O
features	O
from	O
Steamworks	O
,	O
including	O
automatic	O
updates	O
,	O
downloadable	B-Protocol
content	I-Protocol
,	O
and	O
community	O
support	O
.	O
</s>
<s>
The	O
game	O
supports	O
cross-platform	O
play	O
between	O
the	O
PlayStation	B-Operating_System
3	I-Operating_System
,	O
Windows	O
,	O
and	O
OS	B-Operating_System
X	I-Operating_System
versions	O
.	O
</s>
<s>
The	O
Steam	B-Application
overlay	O
shows	O
the	O
player	O
's	O
friends	O
on	O
both	O
Steam	B-Application
and	O
the	O
PlayStation	B-Device
Network	I-Device
,	O
with	O
achievements	O
rewarded	O
for	O
both	O
Steam	B-Application
and	O
PlayStation	B-Device
Network	I-Device
Trophies	O
.	O
</s>
<s>
Players	O
can	O
unlock	O
the	O
game	O
on	O
Steam	B-Application
for	O
Windows	O
and	O
OS	B-Operating_System
X	I-Operating_System
for	O
no	O
additional	O
charge	O
.	O
</s>
<s>
The	O
integration	O
of	O
Steamworks	O
on	O
the	O
PlayStation	B-Operating_System
3	I-Operating_System
allows	O
Valve	O
to	O
collect	O
data	O
about	O
problems	O
that	O
arise	O
after	O
shipping	O
and	O
push	O
appropriate	O
updates	O
.	O
</s>
<s>
Valve	O
has	O
stated	O
they	O
do	O
not	O
plan	O
on	O
integrating	O
other	O
PlayStation	B-Operating_System
3	I-Operating_System
features	O
,	O
such	O
as	O
3D	B-Algorithm
television	I-Algorithm
or	O
PlayStation	B-Device
Move	I-Device
support	O
.	O
</s>
<s>
In	O
June	O
2012	O
,	O
Valve	O
announced	O
that	O
the	O
PlayStation	B-Operating_System
3	I-Operating_System
version	O
would	O
be	O
patched	O
later	O
that	O
year	O
to	O
include	O
support	O
for	O
the	O
PlayStation	B-Device
Move	I-Device
motion	B-Device
controller	I-Device
,	O
and	O
to	O
add	O
the	O
additional	O
content	O
that	O
was	O
previously	O
provided	O
with	O
the	O
Hydra	O
,	O
under	O
the	O
name	O
Portal	B-Application
2	I-Application
In	O
Motion	O
.	O
</s>
<s>
A	O
free	O
co-op	O
add-on	O
for	O
the	O
Portal	B-Application
2	I-Application
In	O
Motion	O
content	O
was	O
added	O
in	O
June	O
2013	O
.	O
</s>
<s>
Valve	O
said	O
that	O
despite	O
additional	O
support	O
for	O
PlayStation	B-Operating_System
3	I-Operating_System
over	O
Xbox	B-Operating_System
360	I-Operating_System
,	O
the	O
core	O
game	O
is	O
the	O
same	O
on	O
both	O
platforms	O
.	O
</s>
<s>
As	O
of	O
February	O
2014	O
,	O
SteamOS	B-Application
,	O
Valve	O
's	O
own	O
Linux-based	O
operating	O
system	O
,	O
supports	O
Portal	B-Application
2	I-Application
and	O
its	B-Application
predecessor	I-Application
,	O
as	O
do	O
most	O
modern	O
Debian-based	O
Linux	B-Application
distributions	O
on	O
its	O
services	O
via	O
the	O
Steam	B-Application
client	I-Application
.	O
</s>
<s>
Released	O
as	O
a	O
Beta	O
in	O
early	O
2014	O
for	O
Linux	B-Application
distributions	O
,	O
it	O
holds	O
all	O
of	O
the	O
same	O
traits	O
as	O
the	O
other	O
versions	O
,	O
retaining	O
cross-platform	O
play	O
,	O
split	O
screen	O
and	O
fully	O
native	O
controller	O
support	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
a	O
strong	O
favorite	O
of	O
gaming	O
journalists	O
during	O
closed-door	O
previews	O
at	O
the	O
E3	O
2010	O
convention	O
.	O
</s>
<s>
The	O
Game	O
Critics	O
Awards	O
,	O
selected	O
by	O
journalists	O
and	O
critics	O
,	O
awarded	O
Portal	B-Application
2	I-Application
the	O
title	O
of	O
Best	O
PC	B-Device
Game	O
and	O
Best	O
Action/Adventure	O
Game	O
,	O
and	O
nominated	O
the	O
game	O
for	O
Best	O
of	O
Show	O
and	O
Best	O
Console	O
Game	O
.	O
</s>
<s>
IGN	O
named	O
Portal	B-Application
2	I-Application
as	O
its	O
Best	O
of	O
E3	O
for	O
PC	B-Device
,	O
Xbox	B-Operating_System
360	I-Operating_System
,	O
and	O
PlayStation	B-Operating_System
3	I-Operating_System
systems	O
and	O
Best	O
Puzzle	O
Game	O
,	O
and	O
nominated	O
it	O
for	O
Best	O
Overall	O
Game	O
.	O
</s>
<s>
GameSpy	O
named	O
Portal	B-Application
2	I-Application
the	O
Best	O
Overall	O
Game	O
and	O
Best	O
Puzzle	O
Game	O
of	O
E3	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
won	O
the	O
2010	O
Spike	O
Video	O
Game	O
Award	O
for	O
"	O
Most	O
Anticipated	O
Game	O
for	O
2011	O
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
received	O
universal	O
acclaim	O
upon	O
release	O
.	O
</s>
<s>
Several	O
reviewers	O
identified	O
Portal	B-Application
2	I-Application
as	O
an	O
early	O
contender	O
for	O
"	O
Game	O
of	O
the	O
Year	O
"	O
,	O
while	O
others	O
called	O
it	O
one	O
of	O
the	O
best	O
games	O
of	O
all	O
time	O
.	O
</s>
<s>
Eurogamers	O
Oli	O
Welsh	O
said	O
that	O
the	O
game	O
avoids	O
the	O
normal	O
pitfalls	O
that	O
developers	O
introduce	O
in	O
sequels	O
,	O
stating	O
that	O
"	O
Portal	B-Application
is	O
perfect	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
is	O
not	O
.	O
</s>
<s>
Club	O
wrote	O
that	O
with	O
Portal	B-Application
2	I-Application
,	O
Valve	O
had	O
alleviated	O
any	O
doubts	O
that	O
"	O
Portal	B-Application
could	O
be	O
expanded	O
into	O
a	O
big	O
,	O
narrative	O
experience	O
with	O
all	O
the	O
bells	O
and	O
whistles	O
of	O
a	O
mainstream	O
gaming	O
hit	O
"	O
.	O
</s>
<s>
Dan	O
Stapleton	O
of	O
PC	B-Device
Gamer	O
was	O
able	O
to	O
predict	O
many	O
of	O
the	O
plot	O
twists	O
within	O
Portal	B-Application
2	I-Application
story	O
but	O
"	O
still	O
looked	O
forward	O
to	O
witnessing	O
exactly	O
how	O
the	O
characters	O
would	O
react	O
"	O
;	O
he	O
praised	O
the	O
development	O
of	O
the	O
characters	O
,	O
as	O
"	O
their	O
charm	O
makes	O
what	O
would	O
otherwise	O
be	O
an	O
empty	O
and	O
lifeless	O
world	O
feel	O
boisterous	O
and	O
alive	O
"	O
.	O
</s>
<s>
In	O
contrast	O
,	O
Peter	O
Bright	O
of	O
Ars	O
Technica	O
wrote	O
that	O
compared	O
to	O
the	O
loneliness	O
and	O
despair	O
he	O
felt	O
while	O
playing	O
the	O
first	B-Application
game	O
,	O
the	O
characters	O
,	O
Wheatley	O
and	O
GLaDOS	O
,	O
lost	O
some	O
of	O
this	O
feeling	O
and	O
"	O
the	O
inane	O
babble	O
served	O
only	O
to	O
disrupt	O
the	O
mood	O
"	O
.	O
</s>
<s>
Portal	B-Application
2s	I-Application
additional	O
gameplay	O
elements	O
,	O
like	O
light	O
bridges	O
,	O
lasers	O
,	O
and	O
the	O
gels	O
,	O
were	O
praised	O
as	O
appropriate	O
additions	O
to	O
the	O
game	O
.	O
</s>
<s>
Reviewers	O
were	O
pleased	O
with	O
the	O
difficulty	O
of	O
the	O
puzzles	O
throughout	O
the	O
game	O
,	O
which	O
appeared	O
visually	O
complicated	O
at	O
first	B-Application
but	O
had	O
uncomplicated	O
solutions	O
.	O
</s>
<s>
Tom	O
Hoggins	O
of	O
The	O
Telegraph	O
praised	O
the	O
manner	O
with	O
which	O
these	O
elements	O
were	O
introduced	O
through	O
a	O
"	O
brilliant	O
learning	B-General_Concept
curve	I-General_Concept
of	O
direction	O
,	O
rather	O
than	O
instruction	O
"	O
,	O
and	O
considered	O
it	O
a	O
"	O
design	O
ethos	O
that	O
is	O
supremely	O
generous	O
,	O
but	O
dealt	O
with	O
marvellous	O
economy	O
"	O
.	O
</s>
<s>
Bright	O
felt	O
that	O
Portal	B-Application
2	I-Application
was	O
easier	O
than	O
its	B-Application
predecessor	I-Application
,	O
in	O
part	O
that	O
he	O
felt	O
much	O
of	O
the	O
game	O
was	O
effectively	O
tutorials	O
for	O
the	O
new	O
gameplay	O
additions	O
,	O
requiring	O
"	O
careful	O
use	O
of	O
the	O
tools	O
provided	O
"	O
,	O
leaving	O
him	O
with	O
the	O
impression	O
that	O
"	O
the	O
game	O
was	O
on	O
rails	O
"	O
.	O
</s>
<s>
In	O
Portal	B-Application
2	I-Application
,	O
communication	O
is	O
vital	O
to	O
success	O
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
praised	O
for	O
the	O
amount	O
of	O
detail	O
in	O
its	O
design	O
,	O
sound	O
,	O
and	O
music	O
.	O
</s>
<s>
Onyett	O
was	O
impressed	O
with	O
the	O
amount	O
of	O
visual	O
details	O
and	O
capabilities	O
Valve	O
achieved	O
from	O
their	O
Source	B-Application
game	I-Application
engine	I-Application
and	O
that	O
the	O
added	O
details	O
and	O
animations	O
of	O
the	O
levels	O
"	O
consistently	O
serv[ed]	O
not	O
only	O
to	O
entertain	O
the	O
eye	O
but	O
to	O
expand	O
our	O
understanding	O
of	O
the	O
game	O
's	O
characters	O
"	O
.	O
</s>
<s>
Hoggins	O
wrote	O
that	O
the	O
game	O
's	O
world	O
reacted	O
to	O
the	O
player-character	O
Chell	O
's	O
presence	O
"	O
in	O
a	O
startlingly	O
organic	O
way	O
"	O
,	O
and	O
praised	O
Valve	O
's	O
design	O
as	O
"	O
an	O
achievement	O
of	O
world-building	O
that	O
compares	O
favourably	O
with	O
BioShock	B-Application
underwater	O
city	O
of	O
Rapture	O
"	O
.	O
</s>
<s>
Some	O
reviewers	O
said	O
that	O
the	O
second	B-Application
act	O
of	O
the	O
game	O
,	O
taking	O
place	O
in	O
the	O
less-structured	O
portion	O
of	O
the	O
old	O
Aperture	O
facilities	O
,	O
may	O
be	O
confusing	O
to	O
some	O
players	O
.	O
</s>
<s>
Young	O
wrote	O
that	O
in	O
the	O
second	B-Application
act	O
,	O
the	O
game	O
"	O
cranks	O
up	O
the	O
difficulty	O
level	O
at	O
a	O
speed	O
that	O
may	O
dishearten	O
casual	O
gamers	O
"	O
,	O
and	O
said	O
that	O
particularly	O
when	O
traveling	O
between	O
chambers	O
,	O
he	O
had	O
"	O
absolutely	O
no	O
idea	O
where	O
I	O
was	O
supposed	O
to	O
head	O
next	O
"	O
.	O
</s>
<s>
Watters	O
also	O
said	O
that	O
it	O
was	O
unfortunate	O
that	O
the	O
game	O
lacks	O
"	O
stand-alone	O
test	O
chambers	O
and	O
leaderboards	O
...	O
but	O
even	O
so	O
,	O
Portal	B-Application
2	I-Application
is	O
not	O
light	O
on	O
content	O
"	O
without	O
these	O
.	O
</s>
<s>
Welsh	O
said	O
that	O
the	O
attempt	O
to	O
recapture	O
the	O
spirit	O
of	O
the	O
song	O
"	O
Still	O
Alive	O
"	O
at	O
the	O
end	O
credits	O
of	O
Portal	B-Application
2	I-Application
"	O
was	O
a	O
mistake	O
"	O
.	O
</s>
<s>
Video	O
game	O
critic	O
Ben	O
"	O
Yahtzee	O
"	O
Croshaw	O
wrote	O
in	O
his	O
Extra	O
Punctuation	O
column	O
that	O
,	O
while	O
Portal	B-Application
2	I-Application
was	O
a	O
"	O
very	O
good	O
game	O
"	O
,	O
it	O
unnecessarily	O
retconned	O
portions	O
of	O
the	O
original	O
game	O
's	O
story	O
,	O
and	O
did	O
not	O
really	O
further	O
the	O
game	O
's	O
concept	O
.	O
</s>
<s>
On	O
April	O
20	O
,	O
2011	O
,	O
it	O
was	O
reported	O
that	O
customers	O
had	O
launched	O
a	O
protest	O
against	O
perceived	O
shortcomings	O
of	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
Users	O
complained	O
that	O
the	O
game	O
was	O
too	O
shortsome	O
saying	O
that	O
it	O
is	O
only	O
four	O
hours	O
long	O
,	O
about	O
the	O
existence	O
of	O
paid	O
,	O
downloadable	B-Protocol
content	I-Protocol
for	O
some	O
versions	O
at	O
launch	O
,	O
and	O
that	O
the	O
Windows	O
and	O
OS	B-Operating_System
X	I-Operating_System
versions	O
were	O
ports	O
of	O
the	O
console	O
version	O
.	O
</s>
<s>
Stephen	O
Totilo	O
of	O
Kotaku	O
wrote	O
that	O
the	O
game	O
lasted	O
nine	O
hours	O
and	O
that	O
the	O
downloadable	B-Protocol
content	I-Protocol
consisted	O
purely	O
of	O
cosmetic	O
add-ons	O
.	O
</s>
<s>
Some	O
journalists	O
said	O
that	O
the	O
minimal	O
impact	O
of	O
The	B-Application
Potato	I-Application
Sack	I-Application
alternative	O
reality	O
game	O
on	O
the	O
early	O
release	O
of	O
Portal	B-Application
2	I-Application
may	O
be	O
influencing	O
the	O
user	O
scores	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
won	O
the	O
title	O
of	O
"	O
Ultimate	O
Game	O
of	O
the	O
Year	O
"	O
at	O
the	O
2011	O
Golden	O
Joystick	O
Awards	O
,	O
and	O
ranked	O
second	B-Application
place	O
on	O
Time	O
's	O
"	O
Top	O
10	O
Video	O
Games	O
of	O
2011	O
"	O
.	O
</s>
<s>
Gamasutra	O
,	O
IGN	O
,	O
Eurogamer	O
,	O
Kotaku	O
,	O
the	O
Associated	O
Press	O
,	O
and	O
The	O
Mirror	O
listed	O
Portal	B-Application
2	I-Application
as	O
their	O
top	O
video	O
game	O
of	O
2011	O
.	O
</s>
<s>
The	O
game	O
received	O
twelve	O
nominations	O
including	O
"	O
Game	O
of	O
the	O
Year	O
"	O
for	O
the	O
2011	O
Spike	O
Video	O
Game	O
Awards	O
,	O
where	O
it	O
was	O
the	O
most-nominated	O
title	O
,	O
and	O
won	O
for	O
"	O
Best	O
PC	B-Device
Game	O
"	O
,	O
"	O
Best	O
Male	O
Performance	O
"	O
for	O
Stephen	O
Merchant	O
,	O
"	O
Best	O
Female	O
Performance	O
"	O
for	O
Ellen	O
McLain	O
,	O
"	O
Best	O
Downloadable	B-Protocol
Content	I-Protocol
"	O
,	O
and	O
"	O
Best	O
Multiplayer	O
Game	O
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
nominated	O
for	O
six	O
BAFTA	O
video	O
game	O
award	O
categories	O
,	O
and	O
won	O
in	O
the	O
"	O
Best	O
Game	O
"	O
,	O
"	O
Best	O
Story	O
"	O
and	O
"	O
Best	O
Design	O
"	O
categories	O
.	O
</s>
<s>
In	O
the	O
inaugural	O
New	O
York	O
Videogame	O
Critics	O
Circle	O
Awards	O
,	O
Portal	B-Application
2	I-Application
was	O
given	O
the	O
top	O
honors	O
for	O
best	O
writing	O
and	O
best	O
acting	O
.	O
</s>
<s>
The	O
Perpetual	O
Testing	O
Initiative	O
add-on	O
was	O
awarded	O
the	O
2012	O
Golden	O
Joystick	O
for	O
"	O
Best	O
Use	O
of	O
DLC	B-Protocol
"	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
nominated	O
for	O
the	O
2016	O
Steam	B-Application
Awards	O
by	O
the	O
Steam	B-Application
community	O
and	O
won	O
the	O
award	O
for	O
“	O
Villain	O
Most	O
In	O
Need	O
Of	O
A	O
Hug	O
”	O
.	O
</s>
<s>
Based	O
on	O
sales	O
data	O
from	O
Amazon.com,	O
Portal	B-Application
2	I-Application
was	O
the	O
best-selling	O
game	O
in	O
the	O
United	O
States	O
in	O
the	O
first	B-Application
week	O
of	O
its	O
release	O
,	O
but	O
was	O
overtaken	O
by	O
Mortal	B-Application
Kombat	I-Application
in	O
its	O
second	B-Application
week	O
.	O
</s>
<s>
According	O
to	O
NPD	O
Group	O
,	O
Portal	B-Application
2	I-Application
was	O
the	O
second-best	O
selling	O
game	O
in	O
the	O
U.S.	O
in	O
April	O
2011	O
,	O
at	O
637,000	O
copies	O
,	O
and	O
the	O
fourth-best	O
selling	O
in	O
May	O
.	O
</s>
<s>
However	O
,	O
NPD	O
does	O
not	O
include	O
sales	O
on	O
Valve	O
's	O
Steam	B-Application
platform	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
the	O
best	O
selling	O
game	O
in	O
the	O
U.K.	O
in	O
the	O
first	B-Application
week	O
of	O
its	O
release	O
,	O
the	O
first	B-Application
number-one	O
for	O
a	O
Valve	O
game	O
.	O
</s>
<s>
It	O
retained	O
the	O
top	O
spot	O
during	O
its	O
second	B-Application
week	O
.	O
</s>
<s>
Portal	B-Application
2	I-Application
was	O
released	O
a	O
few	O
days	O
before	O
the	O
PlayStation	B-Error_Name
Network	I-Error_Name
outage	I-Error_Name
.	O
</s>
<s>
ShopToNews	O
analyst	O
Joe	O
Anderson	O
expected	O
that	O
the	O
effect	O
of	O
the	O
outage	O
on	O
UK	O
sales	O
of	O
Portal	B-Application
2	I-Application
would	O
be	O
mild	O
.	O
</s>
<s>
On	O
June	O
22	O
,	O
Newell	O
announced	O
that	O
Portal	B-Application
2	I-Application
had	O
sold	O
3	O
million	O
copies	O
.	O
</s>
<s>
,	O
Electronic	O
Arts	O
stated	O
that	O
more	O
than	O
2	O
million	O
copies	O
of	O
Portal	B-Application
2	I-Application
have	O
been	O
sold	O
by	O
retailers	O
worldwide	O
.	O
</s>
<s>
In	O
an	O
August	O
2011	O
interview	O
,	O
Newell	O
stated	O
that	O
"	O
Portal	B-Application
2	I-Application
did	O
better	O
on	O
the	O
PC	B-Device
than	O
it	O
did	O
on	O
the	O
consoles	O
"	O
.	O
</s>
<s>
Upon	O
release	O
of	O
the	O
Perpetual	O
Testing	O
Initiative	O
in	O
May	O
2012	O
,	O
Newell	O
stated	O
that	O
Portal	B-Application
2	I-Application
had	O
shipped	O
more	O
than	O
4	O
million	O
units	O
,	O
with	O
the	O
personal	B-Device
computer	I-Device
versions	O
outselling	O
the	O
console	O
versions	O
.	O
</s>
<s>
Overall	O
,	O
Portal	B-Application
and	O
Portal	B-Application
2	I-Application
had	O
together	O
shipped	O
more	O
than	O
8	O
million	O
units	O
.	O
</s>
<s>
In	O
addition	O
to	O
player-created	O
levels	O
,	O
there	O
have	O
been	O
complete	O
mods	O
of	O
Portal	B-Application
2	I-Application
created	O
by	O
users	O
.	O
</s>
<s>
Portal	B-Application
Stories	O
:	O
Mel	O
is	O
a	O
single-player	O
mod	O
of	O
Portal	B-Application
2	I-Application
developed	O
by	O
Prism	O
Studios	O
,	O
a	O
group	O
made	O
up	O
of	O
eight	O
fans	O
of	O
the	O
Portal	B-Application
series	O
.	O
</s>
<s>
The	O
mod	O
was	O
released	O
on	O
June	O
25	O
,	O
2015	O
,	O
for	O
Windows	O
,	O
OS	B-Operating_System
X	I-Operating_System
and	O
Linux	B-Application
systems	O
,	O
available	O
freely	O
to	O
people	O
that	O
own	O
Portal	B-Application
2	I-Application
on	O
Steam	B-Application
.	O
</s>
<s>
Aperture	O
Tag	O
:	O
The	O
Paint	O
Gun	O
Testing	O
Initiative	O
is	O
a	O
single-player	O
modification	O
of	O
Portal	B-Application
2	I-Application
developed	O
by	O
"	O
The	O
Aperture	O
Tag	O
Team	O
"	O
released	O
in	O
2014	O
.	O
</s>
<s>
The	O
mod	O
replaces	O
the	O
portal	B-Application
gun	O
with	O
a	O
gun	O
that	O
can	O
shoot	O
the	O
various	O
gels	O
(	O
mimicking	O
how	O
Tag	B-Application
:	I-Application
the	I-Application
Power	I-Application
of	I-Application
Paint	I-Application
worked	O
)	O
to	O
otherwise	O
various	O
portal-based	O
puzzles	O
.	O
</s>
<s>
Thinking	O
with	O
Time	O
Machine	O
is	O
a	O
single	O
player	O
mod	O
for	O
Portal	B-Application
2	I-Application
created	O
by	O
Ruslan	O
Rybka	O
and	O
released	O
in	O
2014	O
,	O
which	O
gives	O
the	O
player	O
the	O
ability	O
to	O
record	O
actions	O
that	O
can	O
be	O
played	O
back	O
by	O
a	O
duplicate	O
of	O
the	O
player-character	O
,	O
including	O
the	O
use	O
of	O
a	O
second	B-Application
set	O
of	O
portals	B-Application
.	O
</s>
<s>
Portal	B-Application
Reloaded	O
is	O
a	O
single-player	O
mod	O
for	O
Portal	B-Application
2	I-Application
created	O
by	O
Jannis	O
Brinkmann	O
and	O
was	O
released	O
on	O
April	O
19	O
,	O
2021	O
,	O
exactly	O
10	O
years	O
after	O
the	O
release	O
of	O
Portal	B-Application
2	I-Application
.	O
</s>
<s>
The	O
mod	O
gives	O
players	O
the	O
ability	O
to	O
fire	O
a	O
third	O
portal	B-Application
,	O
the	O
"	O
time	O
portal	B-Application
"	O
,	O
to	O
travel	O
between	O
the	O
present	O
and	O
future	O
versions	O
of	O
each	O
test	O
chamber	O
.	O
</s>
