Etch-a-Sketch was a red plastic square-shaped toy with a grey screen. When you turned the two knobs a line would appear on the screen. One dial made the 'cursor' move up and down and the other moved the 'cursor left and right. To draw a complex design took a lot of patience as it was only really possible to draw images with straight lines. Diagonal lines were drawn by carefully moving the up vertical dial and then the horizontal dial. Circles were impossible.
When you were finished with your design, or you'd given up on something that was overly ambitious to start with you cleared the screen by shaking the Etch-a-Sketch up and down. One of the most frustrating things was that you couldn't 'undo' a line if you made a mistake - so you had to start all over again.