The Ankh is a golden key-shaped symbol that appears on the bottom left corner of the screen. It only appears in certain mazes (mostly easier ones). It is here to warn you if the maze can no longer be solved. If it turns red, the maze can no longer be solved and you would have to undo one or more of your moves and/or reset the maze to get through. A message will also flash on the top of the screen saying that the maze can no longer be solved.