What’s Missing? is a drawing game that contains 240 cards with line drawings, sorted by difficulty. In a round, each player takes a card, hides it behind a cardboard screen, and tries to draw another picture on transparent paper placed on top of that card, with the goal being that the drawer wants other players to guess what's on the card.

After finishing the drawing, the drawer shows only the transparent paper to others, and the other players have to guess what's missing on the transparent paper. The player who guesses correctly earns 1 point, with the drawer losing 1 point if no one guesses.

To win, being clever is more important than being a good artist. Young drawers can give other players a clue based on what kind of things are on the card.