Community user warrior_rockk has released his port of Castle of Illusion (Master System version) made in BennuGD, along with the engine and some tools he developed to edit stages for the game.
Originally, his plan was to release the engine once the port was completed, but porting all the stages is taking much time, so he decided to release it now and use it as the base for his future games.
Gameplay Video: https://vid.me/lhTX
Debug Mode Video: https://vid.me/9nub
Check the forum post (in spanish): http://forum.bennugd.org/index.php?topic=4420.0;topicseen