Exact by design
Wins use exact rational arithmetic. No floating-point guesswork or tolerance.
Expression puzzle for iPhone + iPad
Make 24.
Beautifully.
Combine four number tiles using exact arithmetic, square roots, factorials, and degree-mode trigonometry. Every original number is used exactly once.
1
3
4
6
6 ÷ (1 − 3 ÷ 4)= 24
Why 24++
A puzzle table, not a calculator.
Classic to geek
Explore Classic, Transform, and Trig labs with operator rules that stay clear and finite.
Built for exploration
Tap or sweep across tiles, undo freely, reveal progressive hints, and compare your operation count.
Full Lab
Version 1.0.3: Traditional Chinese, with the same Duo controls.
Version 1.0.1 and later include 72 free puzzles: 24 per lab, using numbers 1–13. Version 1.0 includes the original 24 free puzzles. Full Lab remains an optional one-time purchase for the complete bank and future bank updates, with Family Sharing and Restore Purchases through Apple.
Rotate or unfold iPhone Duo while solving. Number tiles and the operator tray adapt to the available space, keeping your current calculation. Exact arithmetic, puzzles, purchases, and progress sync stay the same. Read the updated guide.