In what sense is there a "progress to higher difficulty levels"? I am at level 23 and it stops getting any harder once it gets to 6 colors, it just stays at 6. It needs to announce I've won at some point or keep getting harder.
Darnit, you know what I'd like to see? A mastermind game where you can choose freely the number of colors to choose from (so not necessarily 6 or less than 6 but anything between 2 and 256 maybe!), and the length of the code (so not necessarily 4, but anything between 2 and 256 again), and the number of guesses. Or better yet, for it to actually estimate the number of guesses you should need to determine the combination given the number of colors and the length of the sequence, and actually give you recommendations on what would constitute an "easy", a "medium" and a "hard" game under those parameters. Now THAT would be something NEW. And it would not even make it harder to create! Except for the utility where it recommends numbers of guesses for different skill level, that's combinatorics and information theory and it's probably NP complete. But a game that just allows the user to set the parameters like that wouldn't be hard to make.
But hey, at least it doesn't have any horrible bugs like the last one I just played a few minutes ago. This, it works the way the parker brothers game works, it's just not very interesting or fun to play, especially what with the mistaken notion of what constitutes an easy and what constitutes a hard skill level.
Nope, I think the only reasonable mastermind game is the one on armorgames based on the mastermind animation - which amazingly enough seems to be designed for newgrounds but it's apparently not here any more. Weird. What's great about it is its atmosphere.
Ima let you in on a little secret though. If you give me 8 turns and 6 colors and a length-4 sequence, I will never lose. In fact I'll never lose if you give me 6. So an infinite number of levels with 8 turns each is not getting to a higher difficulty level. If I have time to think. I learned that on the armorgames one (only just learned this last week that mastermind is an actual board game, now it makes sense, that the maker of the mastermind videos would make a mastermind game, to make a pun out of it).