chore: add nix deps. management

.envrc

@@ -0,0 +1 @@
+use nix

README.md

@@ -1,2 +1,21 @@
 # SnakeDL3
 a game of snake written in the brand new SDL3/C
+
+
+## running the game
+
+this game uses [nix](https://nixos.org/) to manage dependencies.
+
+after downloading nix, you can simply clone the repository, enter the directory
+with direnv enabled and you will automatically get all the dependencies needed.
+
+if you don't have direnv, you can run 
+```bash
+    $ nix-shell .
+```
+to enter a shell with the required dependencies.
+
+after this, you can run the game by typing
+```bash
+    $ make run
+```

shell.nix

@@ -0,0 +1,7 @@
+{ pkgs ? import <nixpkgs> {} }: pkgs.mkShell {
+    nativeBuildInputs = with pkgs; [
+        libgcc
+        sdl3
+        gnumake
+    ];
+}