Add README

README.md

@@ -4,11 +4,11 @@ Demo of basic shapes collisions using the library SGP.
 
 # Building & installing
 
-To build `shapecollisions` we need the `sdl2` and `sdl2_ttf` libraries.
+To build `shapecollisions` we need the `sdl2`, `sdl2-gfx` and `sdl2_ttf` libraries.
 In Debian/Ubuntu/Elementary we can install it with: 
 
 ```bash
-sudo apt install libsdl2-ttf-dev
+sudo apt install libsdl2-dev libsdl2-gfx-dev libsdl2-ttf-dev
 ```
 We also need the library `SGP`:
 https://git.clibre.io/sgp/sgp