Thank you so much for the feedback and I'm glad you enjoyed it :)
It looks like it was a minor bug with the demo level cap, thank you for pointing that out <3
If you're referring to being able to mark cells with "X" then it's both possible to do so with using right mouse click and toggling this button to switch to "X" for left mouse clicks. Might need to find a better design to indicate this to the player...
Regarding the difficulty it's something I'm trying to figure out how to balance, because I want there to be a natural difficulty progression as you complete more levels but it's slightly difficult to determine when I'm also creating the puzzles. From the first 100 players that have played it looks like there are a few outliers that I'll need to take a look at and polish before the full release.
I've also considered changing the puzzle naming so it's not Easy, Medium, Hard and Extreme, but instead 6x6, 8x8, 10x10 and 2 Monks and instead each puzzle would get a difficulty tag regardless of board size as Easy, Medium, Hard and Extreme depending on the data which would give the player a better sense of the actual puzzle difficulty.
