What it teaches
Sums and differences inside twenty, in both directions — 8 + 5 and 13 − 5 are the same fact seen from two sides, and the game asks for both. This is the range the Polish podstawa programowa sets for klasa I, and the range an English Year 1 classroom calls "number bonds within 20".
The aim is recall, not counting. A child who counts on their fingers to 13 is doing arithmetic correctly and slowly; the point of practice is that the answer eventually arrives without the counting.
How it works
A sum appears with a number pad under it. There is no clock, no countdown and no pressure to be quick: timed drills are a documented cause of early maths anxiety, so nothing in the maths games counts down.
A wrong answer does not pass. The task stays on the screen and the help grows. The first miss says only "not yet". The second brings a picture — counters, or a ten frame, which is the frame most classrooms use. The third shows the answer and asks the child to type it, so the last thing that happens is still the child writing the right number.
The sum is worth ten points first time and four after a miss, and it comes back in tomorrow's review either way.
What to look for
Watch for the crossing of ten. Most children are steady on 5 + 3 and slow on 8 + 5, because the second one crosses a ten and the first does not. If that is where the pauses are, the ten frame in the second hint is the picture to talk about.
When the answers come back quickly and without counting, move to Adding and taking away to 100. There is no hurry: this range is worth a whole year.