I only could suggest, for hackers don't show hints of code shapes (for engine consoles), just make less buttons, so for example, just 64 possible variants, so real hacker could just find code by brute force.
Other possible idea, sough harder to implement, to use rotating dials and issue some shake of screen when approach right number on some dial.
I only could suggest, for hackers don't show hints of code shapes (for engine consoles), just make less buttons, so for example, just 64 possible variants, so real hacker could just find code by brute force.
Other possible idea, sough harder to implement, to use rotating dials and issue some shake of screen when approach right number on some dial.