In Schlafmütze, players try to dump the cards from their personal draw piles as quickly as possible, preferably by dumping them on other players.
The deck consists of one hundred cards, with five copies each of cards numbered 1-20. Place the five 1s in the center of the table, then shuffle the remaining cards and deal them out among the players, with each player forming a face-down draw pile. On a turn, a player first sees whether she can play the top card of her discard stack onto a pile in the center of the table (with numbers always being placed in ascending order) or on an opponent's discard pile (with both ascending and descending plays being valid). After this, the player draws her top card and plays it in a similar manner, if possible. If a player has a choice of location, she chooses as she wishes.
If someone makes a mistake when playing a card, any opponent can shout "Schlafmütze", then all of the opponents give the top card of their deck to the player who goofed.
If a player empties her draw deck, she flips over her discard stack at the start of her next turn. As soon as a player is out of cards, that player wins the game.
Schlafmütze is a slightly altered remake of a traditional card game, so no designer is credited for it.