I remember I learnt this when I was 7yo but I am going to teaching our (almost) 2.5yo son addition & subtraction. No, I’m not kiasu, I only teach when I see interest in him, like I always say, it is easier to teach when he is ready. How I know he is ready? He started playing this game and I heard “chirping” sounds more than “thunders”. Don’t understand? Download it from iTunes, it is free.