You mentioned your ds doesn't ask for math worksheets - I'm a scientist and I love love love math. There are a heck of a lot of people who love math and are talented at math who really aren't turned on by worksheets.
Oh believe me, I know, I only mentioned worksheets a bit tongue-in-cheekily after having read recently of gifted kids who seriously love math so much that they ASK to be taught it, and do stuff like ask for math workbooks for Christmas. That is soooo not my son! But yes, he likes solving 3d puzzles like Hanayama metal puzzles and playing games like Rush Hour. Basically he likes anything visual-spatial / concrete / 3d manipulative. His favorite thing in the world is Minecraft and he's very very good at it. He creates insane redstone creations that leave even much older kids in the dust.
