The Sonji Triangle is a giant triangle that is a verse. It is two dimensional, but since it doesn't exist, it can contain 4 dimensional objects.
This verse's outside is two dimensional, but the inside is four dimensional. There are no layers. The reason it is a triangle is because the gravity is triangular. This type of gravity is known as irregular gravity, as it is gravity that doesn't create hydrostatic equilibrium.
This triangle used to be collidable, so somebody decided to paint a smiley face on it. Then, since there was a massive shake in reality, the Sonji Triangle became noncollidable, so no one else could paint on it. Therefore, the smiley face is stuck forever. It is unknown who put the smiley face on it.