diff --git a/README.md b/README.md
index a3e7a54..cf091be 100644
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+++ b/README.md
@@ -2,3 +2,55 @@
 
 # template_project
 Basic setup for building something with app.h on Windows/Linux/Mac/Web
+
+## Building
+
+No build system is used, simply call the compiler from the commandline.
+
+
+### Windows
+
+From a Visual Studio Developer Command Prompt, do:
+```
+  cl source\main.c
+```  
+
+
+### Mac
+
+```
+  clang source/main.c `sdl2-config --libs --cflags` -lGLEW -framework OpenGL -lpthread
+```
+
+SDL2 and GLEW are required - if you don't have them installed you can do so with Homebrew by running
+```
+  brew install sdl2 glew  
+```
+
+
+### Linux
+
+```
+  gcc source/main.c `sdl2-config --libs --cflags` -lGLEW -lGL -lm -lpthread
+```
+
+SDL2 and GLEW are required - if you don't have them installed you can do so on Ubuntu (or wherever `apt-get` is available) by running
+```
+  sudo apt-get install libsdl2-dev
+  sudo apt-get install libglew-dev
+```
+
+
+### WebAssembly
+
+Using WAjic:
+```
+  wasm\node wasm\wajicup.js source/main.c main.html
+```
+You can embed asset files in the process with the -embed parameter. 
+
+A WebAssembly build environment is required. You can download it (for Windows) here: [releases/tag/wasm-env]([../../releases/tag/wasm-env](https://github.com/mattiasgustavsson/dos-like/releases/tag/wasm-env).
+Unzip it so that the `wasm` folder in the zip file is at your repository root.
+
+The wasm build environment is a compact distribution of [node](https://nodejs.org/en/download/), [clang/wasm-ld](https://releases.llvm.org/download.html),
+[WAjic](https://github.com/schellingb/wajic) and [wasm system libraries](https://github.com/emscripten-core/emscripten/tree/main/system).