Bulls and Cows (BullsCows)

Computer (AI) thinks of 4-bubbles secret combination. The bubbles must be all different. Player (Guesser) try to figure that bubble combination by guessing combination containing the same number of bubbles. Computer responds with the number of Cows & Bulls for each guessed bubble combination.

"Cow" means a bubble in the wrong position, while "Bull" means a bubble in the right position. The game would continue until user scores "4 Bulls" for guessing bubble combination exactly.