What it teaches
Typing anything, not just words. The rungs go small letters, a capital at the front, letters with numbers, one symbol, then all of it at once. By the fifth a child can type anything a grown-up is ever asked to type — which is the point, because the first thing they will be asked for is a password.
Shift is the real lesson. It is the first key a child meets that changes what the other keys do, and nobody explains it: they are told "hold shift for a capital" and left to find the rest by accident.
How it works
The word appears one box per character, so a child can see exactly where they are. The next key lights up on the keyboard, and when that key needs shift, shift lights up too.
The keyboard is the whole one — number row, working shift, symbols above the digits. Pressing shift visibly changes every key at once, which is the thing being taught. A wrong key is refused and nothing already typed is lost.
What to look for
Correct fingers do not matter yet. Finding the keys does, and a child who has to hunt for every one cannot write anything longer than a word.
On the strict settings the next key is not lit. That turns this into a test, which is the right thing for a child who has already done the first three rungs easily.