The rule changes under you.
A word says which question to answer. A moment later the thing to answer it about appears, and you press. Half the time the question has moved since the last one.
A block runs about three minutes and ends on its own. Before the first one, a short warm-up settles the two answers into your hands and is then set aside.
Odd or even, against under or over five.
The arrow keys answer, and so do the panels. Escape stops a block.
At the end there are two typical times: one for the trials where the question stayed put, and one for the trials where it had moved. The distance between them is the reading.
The gap between the word and the thing to judge shortens while your answers keep coming out right, and opens again when they stop.
Your blocks
Nothing is written down yet. A finished block leaves one point here, and the run of them is where the reading lives: a single block on its own moves around a great deal.