What it teaches
Adding and taking away inside a hundred. The jump from twenty is not a jump in size, it is a jump in method: 34 + 20 is done by moving tens, and 34 + 28 is done by moving tens and then dealing with what is left over.
This is the klasa II range, and the year in which a child stops treating a two-digit number as one lump and starts seeing the tens and the units inside it.
How it works
The same screen as the twenty game, with bigger numbers: a sum, a number pad, and no clock. The help builds in the same three steps, and the picture in the second step changes to match — tens and units rather than single counters, because that is the structure the answer depends on.
A wrong answer never passes and the question never disappears. Nothing is lost by being wrong except the difference between ten points and four.
What to look for
The tell is where a child slows down. A pause on 40 + 30 means the tens are not yet automatic. A pause only on 47 + 38 means the tens are fine and the carrying is not — a different problem with a different fix.
Children often meet this range before they are fluent inside twenty. If the misses are frequent, going back to Adding and taking away to 20 for a week is not a step backwards, it is the shorter road.