Add build instructions.

README.md

@@ -1 +1,99 @@
 Chirpy is an audio text messaging app.
+
+
+## Requirements
+
+The Chirpy app requires:
+
+  - a 32-bit ARM CPU (ARMv7-A) with VFP coprocessor (VFPv4); and
+  - Android version 4.4 (KitKat) or later.
+
+That means most Android smartphones except the newest ones.
+
+Building Chirpy requires:
+
+  - a [Unix shell and utilities][unix] including [make][];
+  - [GNU Autotools][autotools] (Autoconf, Automake, and Libtool);
+  - [Python][] and [SCons][];
+  - the awesome [LÖVE][] framework;
+  - the [FFTW][] library and [lua-libfftw][];
+  - the [Nu][] library and [lua-libnu][];
+  - the [android-env][] script;
+  - the [DejaVu][] Sans font; and
+  - [Android Studio][].
+
+
+## Build
+
+First, install [Android Studio][].
+
+Then fetch this repository and change into its directory:
+
+    $ git clone https://github.com/eliteraspberries/chirpy.git
+    $ cd chirpy
+
+Download, extract, and patch LÖVE for Android version 11.1:
+
+    $ curl -L -O https://bitbucket.org/rude/love/downloads/love-11.1-android-source.tgz
+    $ gunzip < love-11.1-android-source.tgz | tar -f - -x
+    $ patch -b -p0 < patches/patch-love-11.1-android-source
+
+Copy everything in the `love-11.1-android-source` directory into the
+`chirpy-android` directory, without overwriting files:
+
+    $ cp -R -n love-11.1-android-source/ chirpy-android/
+
+Note the trailing slashes in the command above.
+
+Download, extract, and patch FFTW version 3.3.4:
+
+    $ curl -L -O http://www.fftw.org/fftw-3.3.4.tar.gz
+    $ gunzip < fftw-3.3.4.tar.gz | tar -f - -x
+    $ patch -b -p0 < patches/patch-fftw-3.3.4
+
+Download and extract Nu version 0.5:
+
+    $ curl -L -O https://github.com/eliteraspberries/nu/releases/download/v0.5/nu-0.5.tar.gz
+    $ gunzip < nu-0.5.tar.gz | tar -f - -x
+
+Download lua-libfftw:
+
+    $ git clone https://github.com/eliteraspberries/lua-libfftw.git
+    $ cp -R lua-libfftw/libfftw .
+
+Download lua-libnu:
+
+    $ git clone https://github.com/eliteraspberries/lua-libnu.git
+    $ cp lua-libnu/libnu.lua .
+
+Download the android-env script:
+
+    $ git clone https://github.com/eliteraspberries/android-env.git
+    $ cp android-env/android-env.sh .
+
+Download the latest version of the DejaVu Sans font:
+
+    $ curl -L -O https://github.com/dejavu-fonts/dejavu-fonts/releases/download/version_2_37/dejavu-fonts-ttf-2.37.zip
+    $ unzip -j dejavu-fonts-ttf-2.37.zip dejavu-fonts-ttf-2.37/ttf/DejaVuSans.ttf -d fonts
+
+Build everything:
+
+    $ make apk
+
+Finally, open the project directory `chirpy-android` in Android Studio,
+and select 'Make Project' from the 'Build' menu.
+
+
+[Android Studio]: <https://developer.android.com/studio/>
+[DejaVu]: <https://dejavu-fonts.github.io/>
+[FFTW]: <http://www.fftw.org/>
+[LÖVE]: <https://love2d.org/>
+[Nu]: <https://github.com/eliteraspberries/nu>
+[Python]: <https://www.python.org/>
+[SCons]: <https://scons.org/>
+[android-env]: <https://github.com/eliteraspberries/android-env>
+[autotools]: <https://www.gnu.org/software/automake/>
+[lua-libfftw]: <https://github.com/eliteraspberries/lua-libfftw>
+[lua-libnu]: <https://github.com/eliteraspberries/lua-libnu>
+[make]: <http://pubs.opengroup.org/onlinepubs/9699919799/utilities/make.html>
+[unix]: <http://pubs.opengroup.org/onlinepubs/9699919799/utilities/contents.html>