I run the site mathpuzzle, and used to be the main advisor for the TV show *Numb3rs*. I've contributed extensively to MathWorld. Before that, I wrote the Math Games columns for the MAA. I am now the chief editor for the Wolfram Demonstrations Project. Of my own Demonstrations there, some of my favorites are:
- Mrs. Perkins's Quilts
- Tightly Packed Squares
- Social Golfer Problem
- The Circles Of Descartes
- Triangle Calculator