Update README.md with build instructions + license

README.md

@@ -1,5 +1,5 @@
 # tinyray
-A simple raytracer in exactly 450 lines of C
+A simple raytracer in exactly 450 lines of C-code.
 
 ![Output](output.bmp)
 
@@ -13,6 +13,26 @@ A simple raytracer in exactly 450 lines of C
  * Gradient Background
  * Watermark
  
+### Building
+Find a compiler and build `tinyray.c`. Run the executable and it'll create an image called 'output.bmp' in that directory. Simple as that!
+
+Some examples:
+
+```
+# Building with gcc
+$ gcc tinyray.c -o "tinyray"
+
+# Building with cl
+> cl tinyray.c
+```
+
+tinyray uses [the excellent stb_image_write library](https://github.com/nothings/stb/blob/master/stb_image_write.h) for outputting a bitmap image.
+
+### License
+Public Domain - Do whatever you like!
+
+Credit would be very much appreciated though :)
+
 ### Helpful Resources
 I created this toy raytracer to learn about basic raytracing (and for fun, of course), taking inspiration from the following resources:
  - [Gabriel Gambetta: Computer Graphics From Scratch](https://www.gabrielgambetta.com/computer-graphics-from-scratch/basic-ray-tracing.html)