It was working before, now it just won't start.

Zen of Sudoku is now free-to-pay, but I want to to bind it to my account. Is there any shop where I can buy a Steam key?

When a player fills in a square you should probably make it so that all the numbers that were previously penciled in in that square are removed.

... this might sound strange, but, this short few minutes long tutorial 'taught' me how to really 'play' Sudoku. I always 'knew' the rules as such, but the animation and visualization and even the short text "you do not need to know math ... it's 'just' logic" made me finally 'see' how to approach these puzzles. What to look for and where. Before this game, I always felt 'stuck' one way or another when solving these puzzles in newspapers. Having seen the animations (emphasizing the rows, showing me 'her...

Crowded here huh? Steam achievements would be dope. I need to feel I'm getting somewhere in my life.