How to use this solver:

• Use ↑ ↓ ← → keys to move around the puzzle, or click on a cell
• Black numbers are the starting values and cannot be changed.
• Numbers 1-9 to fill in a number, spacebar or backspace to clear a number
• Press backspace or spacebar to clear the selected cell.
• New! Hold down shift to select multiple cells, escape to clear selection
• Hold + or - keys and press 1-9 to add/remove pencil marks in selected cells.
• Press p to show or hide all pencil marks