Btw, I have luck that one of my japanese friend teach Abacus, and today we went to her home to try if my DS3 like Abacus. My son sit on the table and once my friend show her the equations for calculation, my son took the paper and keep calculation, totally ignore the Abacus =_=, may be he is not yet reach the age for paying attention to instruction. I will wait and see if he want to learn Aabacus when he get older and may try those computer based maths game for him when he is 4.
Thanks everyone for so many good suggestions ^^
