My five-year-old son has been hogging my iPhone and the family iPad all last week while we were on vacation. He loaded tons of “free” games which ended up costing us $10 — (my husband: “Does he know how to read ‘free’?” Me: “Yes, he reads it as ‘fee.’ Hence the charges!) — and we had to yell at him to turn off the screens. Except when we noticed he was playing Math Ninja. True, he’d try to cheat and slyly ask us what 9 + 6 is but we were on to him. It turns out to be a fun game for all my kids including my 10-year-old and 8-year-0ld, both girls. And, I turn out to be bad at it.