iGuess Number - (Cows and Bulls or Mastermind)

About:
This iGuessNumber game is also known as Cows and Bulls or Mastermind. It is a very old game which is starts from UK in middle of 20th century. You can choose how many digits you want to guess and complexity level.

Designed by: Davit Avetisyan

Introduction:
iGuessNumber is usually a game playing between 2 players. At beginning of the game, each player keeps one 4-digit secret number in mind. The number is formed with digits which range from 0 to 9, and each digit cannot be repeated.
During the game, one player (user) proposes a number for guess attempt, the other player (user or device) replies the result compared between the guess and the secret number. The result is composed of how many digits has the player guessed on the same position (first digit) and how many digits has the player guessed at all (noted as second digit).

Example:
The generated secret number is "8043". The first attempt to guess the number was "8602". The result of this first attempt will be "2:1". It means there are 2 digits guessed ("8" and "0" digits exist in secret number), and one of them is in correct position (it is "8").