A very flexible way to compile Agar natively under Windows is using MSYS. Note that MSYS only supports the configure script and the build system, the compiled libraries are completely native and independent.

1. First install the base MinGW components. To faciliate this task, you can download the Automated MinGW Installer from this page.
2. Get the MSYS installer from the MinGW download area, and proceed with the installation. You will probably want to install the gdb package as well if you are going to be developing applications.
3. If you are using Windows x64, as of MSYS-1.0.10, the following fix is required otherwise the MSYS shell will not start!
4. Download the latest release from the SDL 1.2 series and install:

     $ tar -xzf SDL-1.2.x.tar.gz
     $ cd SDL-1.2.x
     $ ./configure && make && make install
   

5. (Optional) The built-in font engine is a low-quality bitmap engine. Installing FreeType is recommended for high-quality, antialiased font rendering. Download the latest source package of the 2.1 series (or later, if you're adventurous) from the freetype download area, and install:

     $ tar -xzf freetype-2.1.x.tar.gz
     $ cd freetype-2.1.x
     $ ./configure && make && make install
   

6. At this point, you should be ready to compile and install Agar. Go to the Agar source directory and issue:

  $ ./configure && make && make install