Edit code/document with real-time collaboration.

Automatic live view of the changes made to HTML, JS, CSS.

C code for most of the programs that appear in HD (Hacker's Delight)

This site is an adjunct to the book Hacker's Delight (Addison-Wesley, 2003)

SSD storage

Tactile touchscreen surface with physical buttons that rise up from the surface on demand, and then recede back into the screen.

Mathics is a free, general-purpose online computer algebra system featuring Mathematica-compatible syntax and functions. It is backed by highly extensible Python code, relying on SymPy for most mathematical tasks and, optionally, Sage for more advanced stuff.