Online engineering/scientific books (like this one) need interactive tools/examples. JavaScript seems a proper tool for creating such examples. I use JavaScript libraries such as JSXGraph, MathBox and plotly.js to create interactive examples. Some are as follows.

## Math

- Eigenvectors and eigenvalues of 3-by-3 matrices
- Change of basis in 2D
- Change of basis in 3D
- Rotation in 2D
- Rotation in 3D
- Rotroinvestion
- Eigenvalues and transformation of a circle
- Eigenvalue and transformation of a sphere