Guess The Number

Find the hiidden number in the minimum of tries. It's a 4-digit that does't contain a 0. And every digit appear only once in the sequence. Enter your suggestion and the app will automatically generate a sort of correction. It's a combination of 'x' and 'X'. 'x' means that a digit in your sequence is in the hidden number. 'X' means that it is in it's correct place.
The number of 'x' and/or 'X' determines the number of digits guessed.