_Mem_ is following the idea and the rules of the board game _Memory_. 40
cards are placed randomly in a rectangular grid of the size 5×8. Each symbol
is included in the cards twice. The goal is to find as many pairs of symbols
as possible. Each turn, a player is allowed to turn two symbols, and if they
do not match, turn them face down again.
The game is a single player game only, with the challenge to solve the board
with as few tries as possible. There is no-multiplayer mode and no computer
opponent to battle. Found pairs do not vanish, but stay visible on the field.
If a board is cleared the score is shown and you can begin again.