Layers

Every shape lives on a numbered GDS layer. The Layers panel shows one row per layer:

• Color chip — click to edit color, fill pattern, and mask field tone (see below).
• Eye — toggles visibility. Hidden layers are not selectable.
• Lock — prevents editing shapes on that layer.
• Radio dot — the active layer. New shapes go here, inheriting the active layer's datatype.
• Up / Down chevrons — reorder z-priority within the viewport. You can also drag a layer row by its handle to move it to any position in the list (one undo step).
• Name — editable inline (double-click to rename, Enter to commit, Escape to cancel).
• id/datatype badge — the layer's GDS number and datatype. Click to retag (type N to change just the layer number, or N/M to set both); new shapes drawn on this layer inherit whichever pair you land on. Retagging migrates every shape already on the old pair onto the new one, across every cell in the document — not just a rename of the row. It refuses a pair that collides with another declared row, and if the target pair already holds shapes of its own it asks to merge first, naming both counts. The whole move (row, migrated shapes, and the active-layer pointer if it was the retagged row) is one undo step.
• Deleting a layer row cascades. The delete button removes the row and every shape on that exact layer/datatype pair, across every cell — as the confirm says. A single Undo restores the row, the shapes, and their original stacking order.
• Tone badge (DF / CF) — shown when the layer declares a mask field tone: DF (dark field, filled badge) = drawn shapes become chromium; CF (clear field, outlined badge) = drawn shapes become the openings. Set it in the colours dialog. This is app-level metadata that travels with the layer-setup JSON and the document — it records the single most consequential per-mask decision without changing geometry.
• Shape count — the small number to the right of the id/datatype badge is how many shapes are on this layer in the active cell. Layers with zero shapes appear dimmed (KLayout-style "used vs unused" hint), so you can tell at a glance which layers carry geometry without expanding everything.
• Hollow toggle (○ / ◌, hover-revealed) — switches the layer between solid fill and outline-only rendering. Useful when many layers overlap and you want to see edges through one another.
• Opacity slider (hover-revealed, 0–100% in 5% steps) — multiplies the fill alpha for that layer. The stroke is left alone, so even at 0% opacity the layer is still distinguishable by its outline.

Use the + button at the top of the panel to add a new layer.

Clicking a layer row to make it active, and clicking its eye (including the panel header's show-all / hide-all button) to hide or show one or every layer, are view changes only: they cost no undo step and do not mark the file as having unsaved changes — Ctrl+Z still undoes your last real edit, not the click.