The D button actually opens the dungeon editor.
In my rush to get the game uploaded for the Ludum Dare in time I forgot to remove my editors, you can even press the M button to open the map editor. :S
Sorry about the difficulty; I wanted to implement some kind of difficulty curve to the dungeons but, due to the time limit and inexperience with creating randomly-generated games, I didn't manage to ge that done in time. Something I'd definitely keep in mind incase I make a post-jam version.
Thanks for playing our game!