This is a game of sudoku, which I tried to make more fun by automating the most boring part - counting. You still have to think, but no more manual counting of what numbers are allowed in each cell. You could only click on possible numbers. You still could loose (reach a dead end), where there are no possible solutions. In such case you could undo some moves and try to fix your mistake.
Built using sudoku.js library & some CSS tricks.