Type in a number and test it. Up to 4 panels will light up. Each panel lights up if the number satisfies its own special rule.

Which lights you can switch on? Can you make all four lights light up at once? If not, why not?

If you find an example where it's impossible to light them all up, send us the four rules and explain why it's not possible.

If you find an example where it is possible to light them all up, send us the four rules and the numbers that work.

What is special about your numbers? What is the smallest number which lights them all up?

Tap on *Change Rules* for a new set of rules.