- Select 'Easy', 'Medium' or 'Tricky' to make a new rule.
- Enter an input number and leave the output number blank, then press 'Calculate' to see what output
number the rule gives. Press 'Record' to keep the result to refer to
later. Keep doing this until you think you know what
the rule is.
- Enter a new input number and the output number you
think the rule will generate, then press 'Check'. You must do this
twice in a row to win.
Note that a rule can be written in different ways. You might have
written the rule differently than the computer, but still be