Thanks, LMom! I don't think my DS is ready for Math Detective yet, it's grade 3-4. But Zaccaro looks good. I'm looking for practice that's fun, and that reinforces his basic math skills. I can see that he hasn't committed a lot of basic math to long term memory yet. (the concept of long and short term memory discussed in that NY Times article really helped me understand the issue). I think I will order this one. Thanks.