Fair criticism. I appreciate the feedback! I thought I made the backspace key work on Sudoku. I'll look into that. I know "E" works for erase. Just checked it and if the incorrect answer is selected, you can press "E" or "delete"/"backspace" and that should clear the incorrect answer. As for the fail counter, it's so that the leaderboards are fair. If someone can just faceroll the keyboard to solve the puzzle quickly, it's not really fair for the leaderboards. But I get it. Sudoku isn't typically really a competitive puzzle and when doing them on paper, you often will erase wrong answers and keep going.