Next Number shows three numbers in a row, such as 7, 8, 9, and asks what follows. It is a short step from reciting numbers to really knowing where each one sits.
What your child is learning
Many young children can chant from one to twenty without being able to start in the middle. Ask "what comes after twelve?" and they need to begin again at one. This game practises picking up the count from anywhere, which is the foundation for adding on later.
About a third of the questions count backwards. Counting down is harder and matters just as much, because it is how children first make sense of taking away.
How to help
Read the three numbers aloud together with a steady beat, then pause. The rhythm often carries the answer out by itself.
For the backwards questions, point out the word on the board. Try counting down on fingers, folding one away each time.
If your child is unsure in the teens, that is normal. The words "eleven", "twelve" and "thirteen" do not follow the pattern of the later numbers, and they take time. Say the whole run from ten to twenty together now and then.
A number line helps a great deal. Draw one on paper from 0 to 20 and let your child find the three numbers and hop to the next.
Taking it further
Play it in the car without a screen. Say three numbers and stop. Let your child set questions for you too, and get one wrong on purpose. Children love correcting an adult.
For HTML5 games that teach early maths, this one is very short: eight questions take a couple of minutes.