Layers

Layouts are drawn on layers. In GDSII a layer is identified by two numbers, the layer and the datatype. laylight gives them names in a layer table:

define layer {
    si    { gds 1/0 }
    metal { gds 10/0 }
}

A cell draws on a layer with a layer <name> { ... } block, and every shape defined in the block belongs to that layer. A cell can have as many layer blocks as it needs, in any order.

The preview gives each layer its own color.

Real projects keep the layer table in a file of its own and import it. From the next chapter on, the tour's programs start with import "tech.lyl", a small table with the layers si, slab, sio2, metal and marker; its tab sits next to your file in the editor.