This publication unfolds along the lines of Bridget Riley's (born 1931) 2018 exhibition at David Zwirner, London. Beginning with an exploration of black-and-white equilateral triangles, Riley leads the viewer into an awareness of the ways in which a surface--wall or canvas--can affect a seemingly simple form: the triangle. While demonstrating these subtle changes, she manipulates this form by bending its sides. Riley is revisiting and developing works which she initiated over 50 years ago, as is shown here by the inclusion of Black to White Discs (1962/1965). This diamond formation of discs, which graduates in tone from white to black and back again, offers a lead-in to her new body of work. In Cosmos and the Measure for Measure series, Riley recalls a group of subtly shaded colors used this time in discs. While the compositions remain fundamentally the same, the play of colors changes every time.