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Small interactive things, most of them built for my own classroom. Free, no login, no ads. They work best on a laptop or tablet.

Interactive Unit Circle

Drag the point around the circle and watch the angle, the coordinates and the trig values move together. The whole of trigonometry in one picture.

A game about graphing: pick the function that hits the targets. Lines first, then quadratics and beyond.

Arrange the numbers 1 to 15 so every neighboring pair adds to a perfect square. Harder than it sounds; there's a reason it's famous.

A number line from zero to a billion. Draw where you think one million goes, then see where everyone else put it, and where it really is.