Effects

Gradient shading is applied on top of everything. There are three gradient modes, Linear Gradient, Radial Gradient, Corner Gradient

You can have a gradient of 8 colors and 8 alpha keys and it will be applied linearly. You can change the rotation of the gradient.

You can have a gradient of 8 colors and 8 alpha keys and it will be applied radially.

You can have 4 colors with alpha for 4 corners of the image. These four colors are linearly blended.

In the gradient picker window, you can choose the gradient mode.

Documentation