Bright Square Goo
Not to be confused with the regular Square Goo, a goo of the same colour.
Bright Square Goo, also known as Pixel, is a unique goo, in terms of design.
The fact that it is square (or a cube) is due to it being set in Chapter 4. Functionally, it is identical to the regular Black Goo, only it appears to hold stronger bonds. It also makes different sounds, has no eyes, and are rarely used. Building in Chapter 4 is executed by using infected goos, and in later levels (E.G Road Blocks) uses Black goos instead. and they are only used in 3 levels:
Bulletin Board System
It's counterpart, the regular square goo, is very different, and the two can be easily confused.