Try to break the code at 4 levels with different difficulty !
Easy: Pick 4 digits from 9 digits(1-9)
Medium: Pick 9 digits from 9 digits(1-9)
Hard: Pick 9 digits from 16 digits(0-9, D, E, F, G, H, J)
Hell: Pick 16 digits from 25 digits(0-9, D, E, F, G, H, J, K, L, M, N, P, Q, S, T, U)
Too difficult for you? You can take it easy! Try playing 'Fun' mode!
In 'Fun' mode, some cells are randomly removed to reduce the difficulty.

Rules:
Correct digit at correct column but wrong row is represented by C
Correct digit at wrong column but correct row is represented by R
Correct digit at correct column and correct row is represented by A
Correct digit at wrong column and wrong row is represented by B

Example:
your guess answer
345 5D8
678 F7G
9EH 03H

result: 1C1R2A1B