Fun game, glad I came back and tried again seems like an update added more variants of guys to find and that's definitely added to the difficulty in a cool way. In some ways it's easier, but since you don't always know the difference you're looking for it can be somewhat harder. A suggestion that you could take or leave is perhaps having a "Target" in the top right corner or something for what the player is looking for, would help them realize the type of difference they're looking for in a level. Not sure if that would make it too easy or not, either way a fun little concept!