Trains continuous working memory. Cards pop up one at a time — have your child hold the most recent card in mind, and if the new one matches the one that just passed, tap the bell fast. The better you get, the faster the cards come. Trains sustained attention and constantly updating memory (1-back) — playable even before your child can read.
Cards pop up in the middle of the screen one at a time — have your child hold the most recent one in mind. If the new card "matches the one that just passed," they should tap the bell before it disappears. A faint image of the previous card sits in the corner to help younger kids remember. The better they do, the faster the cards start changing.
Continuously updating working memory (1-back) — the brain must hold the most recent item, compare it to the new one, then instantly drop the old one and repeat, throughout the whole game. This is a real working-memory training task used in research.
Tips for parents
In the first few rounds, have your child say each card's name out loud ("apple... dog... dog! Same one!"). Once they're comfortable, let them play quietly in their head instead.
It means comparing what you see right now to "one step before it." It's a standard working-memory training task used in research — the adult version, N-back, looks several steps further back.
4-5 year-olds still have very limited working memory, so the faint hint keeps the game fun instead of frustrating. As they grow, they'll naturally stop needing to look at it.
Letting a non-matching card pass without tapping counts as correct, but missing a card that does match counts as a miss — so the game demands constant attention.