Crystal Castles has nine levels with four castles each, and a tenth level which features a single castle — the clearing of which ends the game. Each of the 37 trimetric-projected castles consists of a maze of hallways filled with gems and bonus objects, and also includes stairs, elevators and tunnels that the player can use as shortcuts. The three-letter initials of the player with the highest score are used to form the first level's castle structure. When all gems in a castle have been collected, the player moves on to the next castle. The player can also skip some castles and acquire additional lives and points by using secret warps activated by making Bentley Bear jump at special locations.

[Description from Wikipedia]