Layers

Look, keep. A piece can carry the drawings it was made from, its construction or its grid, laid exactly over it in the same frame. Rest the pointer on the piece and they come up over it, like tracing paper lifted onto a drawing; take the pointer away and they go.

Press a layer’s name and it stays, in red, the way a mark is made on a proof, and the piece steps back so the drawing stands alone. On a phone, a tap on the piece does the same.