In the tile-laying game Castles of Mad King Ludwig, players must building an amazing, extravagant castle for King Ludwig II of Bavaria...one room at a time. You see, the King loves castles, he built Neuschwanstein (the castle that inspired the Disney theme park castles) and others, but now he's commissioned you to build the biggest, and best castle ever - subject, of course, to his ever-changing whims. Each player acts as a building contractor who is adding rooms to the castle he is building while also selling his assistance to other players.

In the game, each player begins with a simple foyer. One player takes on the role of the Master Builder, and that player sets prices for a set of rooms that can be bought by the other players, with him getting to pick from the leftovers after the other players have paid him for their rooms. When a room is added to a castle, the player who built it gets castle points based on the size and type of room constructed, as well as bonus points based on the location of the room. When a room is finished, with all entrance ways leading to other rooms in the castle, the player gets one of seven special rewards.

After each purchasing round, a new player is the Master Builder who sets prices for a new set of rooms. After several rounds, the game ends, then amore points are awarded for completing bonus goals, having the most popular rooms, and being the most responsive to the King's demands, which change each game. The player with the most castle points wins.