The Castle is video game developed by ASCII and released for the SG-1000 in 1986. It is a port of an MSX game of the same name, and is largely identical due to the similar hardware between the two machines. Due to the decline of the SG-1000 and emergence of the Sega Master System, the game was not released in Europe or Australia like many other SG-1000 games.
The Castle was the last SG-1000 game to be released commercially by Sega on a cart, and the only SG-1000 to adopt packaging more akin to Sega Mark III games. The Black Onyx would be the very last SG-1000 game to be released by Sega, but this would be on card.
The game has a fairly standard plot of rescuing a princess from a castle, though the game itself was considered very large for the time. It also contains a map system similar to that of later Metroid and Castlevania games.
The Castle was followed by the MSX/NES game Castle Excellent later in the year. The MSX version was also brought independently to the SG-1000 in Taiwan.