You are looking at a stack of cards containing the stuff you want to memorize. On the front of each card is a question concerning a term or topic to learn, on the back is the corresponding answer. Only one side of the topmost card is visible at a time.

Flips the topmost card so that it's other side becomes visible.

You learned well and knew the answer. Moves the card somewhere to the bottom of the stack.

You knew the answer but where not quite sure. Moves the card up to 20 cards down the stack.

You did not know the answer. Moves the card up to 6 cards down the stack so you will see it again soon.

Reshuffles the entire stack randomly.