an explicit variable name. (Step one to changing the defaults)

First step to #3535

Most of this material is covered elsewhere

Talk more about the features of the language, less comparisons to
other languages. Don't introduce the language using the worst possible
example.

Code generated for the test runner needs to break visibility rules

This reverts commit 6267d8a9.

I feel like I've done this before

This reverts commit 90e3665f.