README.md: update this

README.md

@@ -1,9 +1,78 @@
 Tectonic
 ========
 
-*An embeddable, hackable TeX typesetting engine, powered by TeXLive and XeTeX.*
+*A standalone TeX typesetting engine, powered by TeXLive and XeTeX.*
 
-At least, that’s the vision. We’re still doing the work to make it embeddable.
+Tectonic is [TeX](https://en.wikipedia.org/wiki/TeX) processer forked from the
+[XeTeX](http://xetex.sourceforge.net/) extension of the classic “Web2C” TeX
+implementation. The goal of Tectonic is to provide a *standalone* TeX/LaTeX
+engine that can be embedded anywhere, bringing the power of TeX typesetting to
+any application that needs it.
+
+There are two key differences between Tectonic and other TeX engines:
+
+- The implementation has been fully detached from the classic implementation
+  in the [WEB](https://en.wikipedia.org/wiki/WEB) language and from the
+  associated nest of support tools. Tectonic is written in C, C++, and Rust,
+  and its implementation is self-contained.
+- Tectonic’s I/O backend obtains resources from a Zip file called a “bundle,”
+  so that you don’t need a specialized filesystem tree containing thousands of
+  files in order to process a realistic document.
+
+Tectonic is almost completely derived from XeTeX and relies upon the
+infrastructure developed by the [TeXLive](https://www.tug.org/texlive/)
+project. XeTeX was chosen because it can load modern system fonts and process
+Unicode input files.
+
+
+Current Status and Roadmap
+--------------------------
+
+The Tectonic codebase currently builds a standalone program that works almost
+identically to XeTeX. The most important difference is that it looks for
+support files in a Zip file, rather than searching filesystem trees using the
+[kpathsea](https://www.tug.org/kpathsea/) framework. Tools to generate bundle
+files are provided in another repository.
+
+Tectonic currently only builds on Linux machines, although it should almost
+work on Macs.
+
+The current task is a general rearrangement of the code to isolate and tidy
+the I/O-related layers. These will be replaced with new code that will allow
+the possibility of processing LaTeX documents in fully-embedded fashion,
+namely, without producing the usual assortment of output files (`file.log`,
+`file.aux`, etc.).
+
+There is also a significant need to tidy up the machine-generated C code and
+develop a test suite to validate the system. (Tectonic does pass the TRIP and
+eTRIP tests.)
+
+In the long term, the goal is to tidy up the code as much as possible and
+package the full functionality into an easy-to-use library. Ideally the
+implementation will be ported to pure [Rust](https://www.rust-lang.org/) so
+that it can be compiled for fun targets like
+[WebAssembly](http://webassembly.org/). That will take a great deal of effort,
+however. Modern documentation of the internals (i.e., not literate-programming
+style) would also be nice.
+
+
+Building the Program
+--------------------
+
+To build Tectonic requires:
+
+- C and C++ compilers
+- The [Rust](https://www.rust-lang.org/) compiler and its
+  [Cargo](https://crates.io/) package manager.
+- The [Ninja](http://ninja-build.org/) build system.
+- A Python interpreter.
+- The [pwkit](http://pwkit.readthedocs.org/) Python library for
+  `gen-ninja.py`.
+
+This is way too many requirements and I need to drop some of them.
+
+If you have all those things, you should be able to build the executable just
+by running `./gen-ninja.py`, then `ninja`.
 
 
 Testing Your Build
@@ -13,6 +82,22 @@ For now, just run `tests/run.sh`. Hopefully we’ll be moving to a better test
 rig soon.
 
 
+About the Name
+==============
+
+The name of the project is “Tectonic,” spelled and pronounced like a regular
+word because it is one. Enough with the cutesy obscurantism.
+
+In cases where the name might lead to ambiguities, it should be expanded to
+“Tectonic typesetting.”
+
+If you’re feeling expansive, you can interpret the name as suggesting a large
+change in the TeX world. Or you can think of it as suggesting a salubrious
+offering for weary TeX users. Either way, the root of the word does go back to
+the ancient Greek τέκτων, ”carpenter,” which Donald Knuth — a devout Christian
+— might appreciate.
+
+
 Copyright and Licensing
 =======================