Puzzle
Square-Sum Path
Arrange 1 through 15 in a line so every neighboring pair adds up to a perfect square. There's exactly one way. The 1 to 32 circle is the hard one.
Things to play with
Small interactive math. Some are puzzles, one is a game, one is an experiment that only works if lots of people try it. All free, nothing to install.
Game
Function Blaster
Type an equation, fire the laser, hit the targets. Lines are easy. Then the targets stop lining up, and you'll want a parabola, or a sine wave. An early prototype, and already fun.
Explore
Interactive Unit Circle
All sixteen special angles with their exact values, in degrees or radians. Flip between the ordered pair, cosine, sine, and tangent, or drag the point anywhere on the circle and read the values live.
Experiment
Where does a million belong?
A number line runs from zero to a billion. Draw where you think one million goes. Then see where everyone else put it, and where it really is.