Click a square, or a clue, then type the digits (or use the buttons). Click the same square again, or press Space, to switch between Across and Down. Arrow keys move around the grid. 💡 Hint picks a clue you can do next and says why. ✓ Check shows any wrong squares and how many are right. Tick Mark as I go to have each digit marked as soon as it is typed: a right digit scores a point, and a wrong one is replaced by the right digit (no point), like handing it to a teacher. 👁 Reveal square shows the answer in the highlighted square, without a point. Everyone who opens the same puzzle, or the same puzzle code, gets the same cross number. Standard puzzles are a good start; Harder ones need more steps and more mathematics. Choose the level and Standard or Harder, then 🎲 New puzzle for a fresh one. 🏆 Class competition runs a live competition at this level and tier.