Add readme

Program.cs

@@ -56,7 +56,7 @@ struct FirePixels
 
     static FirePixels firePixels;
 
-    static MiniRandom rng = new MiniRandom(5005);
+    static MiniRandom rng;
 
     static void SpreadFire(int src)
     {
@@ -175,6 +175,8 @@ private static IntPtr WndProc(IntPtr hwnd, uint msg, IntPtr lParam, IntPtr wPara
 
     static int Main()
     {
+        rng = new MiniRandom(5005);
+
         string className = "MyClass";
         IntPtr wnd;
         fixed (char* pClassName = className)

README.md

@@ -0,0 +1,19 @@
+# DOOM fire effect in C#
+
+This is the DOOM fire effect with no dependencies on standard GUI frameworks. Calls into Win32 APIs directly.
+
+This is not idiomatic C# GUI code, but mostly a hack. No sane person writes C# GUI apps like this.
+
+Can be compiled with CoreRT to generate a ~8 kB fully self-contained executable.
+
+To publish with CoreRT simply run the following line from the root of the repo:
+
+```
+dotnet publish -r win-x64 -c Release /p:UseCoreRT=true
+```
+
+The main objective of this was to get this code running on Windows NT 3.51:
+
+![C# fire effect on Windows NT 3.51](win351fire.gif)
+
+Mission accomplished.

nogui.csproj

@@ -29,7 +29,7 @@
 
   <ItemGroup Condition="$(UseCoreRT) == 'true'">
     <LinkerArg Include="/subsystem:windows /entry:__managed__Main" />
-    <PackageReference Include="Microsoft.DotNet.ILCompiler" Version="1.0.0-alpha-29101-01" />
+    <PackageReference Include="Microsoft.DotNet.ILCompiler" Version="1.0.0-alpha-29117-01" />
   </ItemGroup>
 
   <ItemGroup Condition="$(UseCoreRT) != 'true'">