Readme update.

README.md

@@ -1,4 +1,37 @@
-sdl.mod
-=======
+# A libSDL backend for BlitzMax
 
-SDL backend for BlitzMax
+SDL.mod leverages [libSDL](https://www.libsdl.org/) as a replacement for some of the core BlitzMax modules that drive the events and graphics subsystems.
+
+The SDL modules allow for improved graphics window management, more consistent cross-platform events, and extra functionality such as touch and haptic support, as well as acting as a base for taking BlitzMax to new platforms such as Android and iOS.
+
+
+
+## How Does it Work?
+
+SDL.mod 
+
+## Installation
+
+Clone or download the repository source, and extract into your BlitzMax/mod folder. The main folder will be called ```sdl.mod``` and will contain each of the SDL modules.
+
+You can then optionally build the modules, or have them automatically compiled when your application builds (bmk understands whenever dependent modules require compilation, and will add them to the build).
+
+## Requirements
+
+Depending on which platform you are targeting, you may be required to install extra libraries as part of the compilation process. 
+
+### Linux
+
+As well as the usual packages required to build BlitzMax, the following developer packages are required for building the libSDL sources with SDL.mod :
+
+```libasound2-dev libpulse-dev libaudio-dev libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxi-dev libxinerama-dev libxxf86vm-dev libxss-dev libgl1-mesa-dev libesd0-dev libdbus-1-dev libudev-dev```
+
+Although these are required for compilation, the runtime requirements for specific audio libraries are optional.
+
+### Windows
+
+Doesn't require anything extra to build or run.
+
+### macOS
+
+Doesn't require anything extra to build or run.