The features/goals sound great, thank you!

These stood out for me as possibly limiting/offputting for wide general use:

- Not being able to generate files in the same directories as input files, or in multiple output directories

- Not being able to provide command line arguments to tasks, as in just

- The mandatory curly braces syntax (and to a lesser extent, smaller verbosities like mandatory `let` keyword). These seem like conveniences for the implementor rather than ideal UX.

The doc for `build` didn't seem quite complete about what can go in there (one of the examples uses a build keyword inside a build recipe ?)