{{Technology Infobox
| image=FilePortal 1 goo.jpg|250px
| image2=FilePortal 2 goo.jpg|250px
| name=Goo
| alternatenames=
| affiliation=Aperture Science
| type=Contaminated water
| maker=
| usedby=Test Subjects
| entity=
| designer=
| voicedby=
| damage=25/tick or instant kill''Portal 2 Collector's Edition Guide''
| hidei=
| hideu=
| hideg=
{{Quote|For this next test, the humans originally requested helmets to avoid brain injuries. I ran the numbers. Making the goo deadly was more cost effective.|GLaDOS|Portal 2|Filemp coop catapult 201.ogg}}

The '''Goo''',''Perpetual Testing Initiative''https// Name according to Valve employee Steve Kalning also known as '''Contaminated Water''', '''Moat''', '''Toxic Water''' or simply '''Acid''', is a common environmental hazard in both ''Portal'' and ''Portal 2''. It is often found in Testing track|Test Chambers, where it usually functions as a testing element, as well as in various maintenance areas. It also fills the very bottom of Test Shaft 09.

== Overview ==
Goo is usually present within Test Chambers to add a hazardous element to the equation. Any contact with the Goo will result in continuous damage that would eventually kill a Test Subject within a few seconds. In ''Portal'', the death appears as in the ''Half-Life'' series (i.e. the view of the bottom of the Goo pit, with the ability to look around); in ''Portal 2'', the screen simply goes to green.

In ''Portal'', the Goo appears as a mixture of red, green, and brown-colored liquid with a swirled appearance, often with smoke swirling around its presence. In ''Portal 2'', the Goo appears to be mainly brown, though still with a swirled appearance.

Cubes of any kind or Sentry Turrets that have fallen into the Goo are irretrievable.

==Related Achievements==
{|class=wikitable style="vertical-aligncenter;" width=50%
!colspan="2" style="text-alignleft"|''Portal 2 Achievements and Trophies|Portal 2''
|rowspan=2 width=64px|FilePARTNER DROP.jpg
!style="text-alignleft"|Empty Gesture (25G)
|''Drop your co-op partner in Goo while they are gesturing by removing the bridge under them.''

== Behind the scenes ==

The Goo can be seen as the ''Portal'' series equivalent of the radioactive / toxic waste from the ''Half-Life'' series, which serves a similar purpose.

== Gallery ==
=== ''Portal'' ===

FileTestchmb11early.jpg|Early Goo.
FileTestchmb8 early.jpg|Ditto, in early GLaDOS' testing track (Portal) Chamber 08|Test Chamber 08.
FileTestchmb8 early2.jpg|Ditto.
FileTestchmb08.jpg|Goo in Test Chamber 08.
FileTestchmb11.jpg|In GLaDOS' testing track (Portal) Chamber 11|Test Chamber 11.
FileTestchmb a 140009.jpg|In GLaDOS' testing track (Portal) Chamber 18|Test Chamber 18.
FileTestchmb a 1500002.jpg|In a typical maintenance area of the Aperture Laboratories.

=== ''Portal 2'' ===

FilePaint caution sign.png|Warning sign set near Goo at the bottom of Test Shaft 09, showing a human being eaten away by the waste.
FilePortal2 2011-05-23 02-45-12-46.jpg|The same sign in-game.
FileP2TC4.png|Goo in GLaDOS' testing track (Portal 2) Chamber 04|Test Chamber 04.
FileP2TC5.png|In GLaDOS' testing track (Portal 2) Chamber 05|Test Chamber 05.
FileP2TC6.png|In GLaDOS' testing track (Portal 2) Chamber 06|Test Chamber 06.
FileP2TC12.png|In GLaDOS' testing track (Portal 2) Chamber 12|Test Chamber 12.
FileP2TC18.png|In GLaDOS' testing track (Portal 2) Chamber 18|Test Chamber 18.
FileP2TC21.png|In GLaDOS' testing track (Portal 2) Chamber 21|Test Chamber 21.

FilePortal2 2011-05-27 21-25-47-31.jpg|The bottom of Test Shaft 09, filled with Goo.
FilePortal2 2011-05-27 21-26-17-59.jpg|Ditto.
FilePortal2 2011-05-27 21-27-03-23.jpg|Ditto.
FilePortal2 2011-05-27 21-27-31-40.jpg|Ditto.
FilePortal2 2011-05-27 21-27-53-67.jpg|Ditto.
FilePortal2 2011-05-27 22-45-54-79.jpg|Ditto.
FilePortal2 2011-05-27 23-17-59-53.jpg|Goo in Enrichment Sphere 02.
FilePortal2 2011-05-27 23-19-42-04.jpg|Ditto, with another warning sign.
FilePortal2 2011-05-28 23-09-09-76.jpg|Goo in Test Shaft 09 Enrichment Sphere 05|Enrichment Sphere 05, functioning as an intended hazard.
FilePeti goo.png|Goo icon in ''Perpetual Testing Initiative''.

== List of appearances ==
* ''Portal'' {{1st}}
* ''Portal First Slice''
* ''Portal Still Alive'' {{Nc}}
* ''Portal 2''
* ''The Final Hours of Portal 2''
* ''Peer Review''
* ''Perpetual Testing Initiative''
*''Lego Dimensions'' {{Nc}}

== References ==

CategoryPortal 2
CategoryAperture Science testing elements
CategoryAperture Science technology