Which cells are there?

Squares, Hexagons, Triangles, Diamonds, Bricks and Stones (irregular cells). In the "Color by number" card, "Mystery mosaics: the cells" sets them for the whole book ("Mixed: a different kind page after page" is the default); the page toolbar sets one page's cells ("The cells of this page"). Choosing cells for the whole book replaces the choices made page by page (locked pages keep theirs).