On the Subject of Valued Keys
Just how many modules have to be like this?
This module has 4 keys with a value on them. Pressing a key will cause a key's value to increment by 1 and a key's value to decrement by 1. Key values will loop back to 0 if they go above 9 and loop back to 9 if they go below 0.
To solve this module, make all the keys' values equal to the first digit of the serial number. At least one press must be made before the module will solve.