Our Lessons, Simulations, Puzzles, and most other materials are built with interactive features that require an active internet connection. They are tightly integrated with our website, and cannot be downloaded. That said, these materials were designed to use a very small amount of data. Lessons are typically less than 5 MB in size, Simulations less than 2 MB, and Puzzles less than 1MB. This means they will work well even on slow connections, and cost relatively little if your internet access is metered.

Our Videos are delivered using automatic adaptive-quality streaming, and they also cannot be downloaded.

Our PDF Materials may be downloaded, printed, and shared freely among your colleagues or students.