Sudoku

Instructions

• Interaction with cells is done by clicking on one of the 3x3 subcells each representing a value from 1 to 9:
  • Long-click on a cell's subcell to place a value in the cell
  • Short-click on a cell's subcell to toggle a pencil annotation
• The Generate button clears the grid and generates a new proper Sudoku (single solution, all hints required)
• The Clear button clears the value of all non-locked cells
• The Lock button locks all cells with a value
• The Unlock button unlocks all cells
• The Solve button searches for a solution of the current grid
  • Cell values cannot be changed while solver is running
  • Solver can be interrupted by clicking on the same button (labeled "Stop" during computation)
  • If a solution is found, values are displayed
  • If no solution exists, the solver ends (button labeled "Solve" again) but cells are not modified