Delta Tao reported that they had to redo all the code from scratch (the original Dark Castle was written in assembly language); also, they added new rooms,[1] a new difficulty, and an alleged "Secret Level".

[4] Although Color Dark Castle featured almost identical gameplay to Dark Castle, being a remake, Delta Tao also added a few of their own things, such as a new difficulty "Novice" for beginner players, eliminating some of the harder levels in the game and having fewer monsters.

[1] Inside Mac Games complimented Color Dark Castle for including the rooms from the original Dark Castle while also including new elements such as additional rooms that had the effect of making the game come out even better than the original.

On Novice, Beginner, and Intermediate the Black Knight stands up shaking his fist, as a gargoyle takes Duncan to Trouble 3.

On advanced The Black Knight's throne falls off the bottom of the screen, while Duncan dances, and it fades out.