Every round puts a math task on screen together with an answer, and you only have to judge one thing: is it correct? There is nothing to write down and no number to type in. The challenge is making that call quickly, because the game wants you to react fast.
Read the task, work out the result in your head, and compare it with the answer shown. Click or tap true if they match and false if they don't. A careless glance is the usual way to slip, so check every digit before you choose. Since each decision takes only a moment, it makes a handy warm-up for basic arithmetic. If you'd rather sort colors than numbers afterward, try Water Sorting Puzzle.