This Puzzle app let you exercise and improve the ability of observation and deduction when trying to observe the numbers and find the rule behind them. To input the Answer, click into the Question marks, a mini keyboard will automatically appear. The Answer is always a two-digit number, after you input the Answer, the process of checking will automatically start. If the input Answer is not correct, the Question marks will appear again. To see the Rule behind the numbers, click into the Professor Owl on the left. To try another Puzzle, click into the Professor Owl on the right.