Excellent website and links to some other good math software from this page as well. The games are good for helping kids drill math skills. There are a whole variety of games on here, like how shapes relate to each other and to math, word problems, etc.
This site looks great, but its not for a six year old the way the review states. My 1st grader is smart, but the simplest games here are definitely out of her range.
N My second grader is good at math and I found this website above his skill level. Maybe I was missing the easier games. I would recommend for 4th grade an up?
If your kid is gifted then they might figure out it is an educational site in disguise and not like it as much if they are cynical. If your child is run of the mill naive then they'll figure it out when they are older then the gifted kids, if they go on this site they will figure out its educational.