Watch. Add. Remember.

Numbers appear on screen one at a time, each visible for about a second — then it’s gone for good. When the sequence ends, type the total. It’s the digital cousin of Anzan, the flash-arithmetic drill used by abacus students.

Type the sum — it submits automatically on the last digit. Correct: you score and the next sequence starts. Wrong: it counts as a miss. Either way there’s no replay — the numbers only flash once.

Early sequences are three single-digit numbers at a gentle pace. As you score, sequences grow to seven numbers up to 50, and the flash time shrinks from 1.2 seconds to 0.6. The game stops being arithmetic and becomes working memory.

You and your opponent get the same sequences on a 60-second clock. Most correct totals wins; ties break on accuracy, then speed.