Plus & Minus By Belgrano & Munari

Plus and Minus is a visual toy originally created by Giovanni Belgrano and Bruno Munari where the user can overlay a selection from 72 semi-transparent cards to create different images. As you overlay the cards, children and adults can create different scenes.

Originally published in 1970 with the aim to encourage children to compose an infinite number of stories, it has been re-released and is available in select stores and sites.

[Thanks to Lisa Kwon for the tip]