What it teaches
What each of the four operations actually does. To fill the gap in 12 ? 4 = 3 a child cannot calculate their way forward — they have to look at the three numbers and ask which operation could connect them.
It is the best short exercise for the confusion between multiplication and division, because the two are tested against each other on the same three numbers.
How it works
Three numbers appear with a gap between the first two, and four signs to choose from. Tapping a sign fills the gap. Only one is right.
A wrong sign is not accepted and the question stays. The help works the sum through with the chosen sign so the child can see for themselves that it does not reach the number on the right.
What to look for
This is the game that shows up gaps the ordinary sums hide. A child can be fluent at 12 ÷ 4 and still not recognise division when it is the thing being asked for.
It is also short. Six to eight questions is a full round, which makes it a good one for the five minutes before something else.