I made this game mostly for my own enjoyment, since I like to play Mastermind and always wanted to try to code one.
As a fun bonus I decided to use the characters from my Brewing Trouble story. They become unlockable as you progress through the levels, until you get all 12 of them (although you can play until level 99).
My biggest challenges wasn't with the code but having to work with size constraints, especially when it came to drawing the characters.