National Gallery of Art
National Gallery of Art: Wallovers
A wallpaper-designing program that turns your freehand drawing into repetitive patterns. A good introduction to repetition as a design principle and to grid systems.
Thomas Jefferson National Accelerator Facility
Jefferson Lab: Looking for the Top Quark
In Looking for the Top Quark, each player receives six quarks that they hide on a grid. The players use coordinates to find their opponent's hidden quarks. The first player to find all six of their opponent's quarks wins!