# Layers and parameters

A background is a stack of layers, drawn bottom to top. Each layer uses one generator, such as a gradient, an aurora curtain or a treeline, and has its own parameters.

# The layer list

• Add a layer with the + button above the list, or from the command menu (⌘K, then type the generator’s name). A background holds up to 16 layers.
• Reorder by dragging a row, or with ⌥↑ and ⌥↓.
• Hide a layer with the eye button, or M. Hidden layers are still saved; they are only left out of the preview.
• Delete with the bin button on the row, or ⌫. ⌘Z brings it back.
• Duplicate with ⌘D.

# Parameters

Select a layer and its parameters appear in the inspector’s Layer tab. Every parameter has a range and a default, and the generator’s page in the docs says what each one does.

• Drag a field left or right to change it. Hold ⇧ for bigger steps and ⌥ for smaller ones.
• Click a field to type a value.
• Double-click to reset it to the default.
• Seed parameters pick a different random variation of the same look. Press R or the shuffle button for a new one.

A drag is one undo step, however far you move.

# Compositing

The Compositing section sets how a layer combines with the layers under it:

• Blend: the blend mode, such as screen or multiply.
• Opacity: how strongly the layer shows.
• Mix in: the colour space the layer’s colours blend in. OKLab gives even, natural gradients; sRGB matches the classic presets exactly.
• Mask: limits the layer to part of the canvas with a linear or radial fade.

# Changing the generator

The generator menu at the top of the Layer tab swaps the layer’s generator and keeps any parameters the two share. Its colours and compositing stay as they are.