Higher or Lower

The simplest guessing game there is, and three different games depending on how old you are.

I am thinking of a number. You guess, I say higher or lower, you guess again. Everybody knows it, which is exactly what makes it useful — there are no rules to explain, so the whole game is strategy from the first move.

It was the first game I played with my kids that had real thinking in it, and the interesting part was watching what it turned into as they got older. Same rules every time. A different game each year.