Black Holes are not considered good in DoodleJump, or anywhere. Black Holes are rips in the background except in the Space Theme, and are a way to end. If you collide or fall into one, then you go into the point of no return and the game is over. Black Holes do not form in the middle, but they form in the far left or far right side. Although not common, you can jump past one, miss the next platform and fall into the black hole. Black holes are featured in every theme except jungle.
Black Holes in two themes.