diff --git a/flake.lock b/flake.lock
index 135a36e..83db597 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,15 +1,31 @@
 {
   "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1673956053,
+        "narHash": "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "35bb57c0c8d8b62bbfd284272c928ceb64ddbde9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "flake-parts": {
       "inputs": {
         "nixpkgs-lib": "nixpkgs-lib"
       },
       "locked": {
-        "lastModified": 1693611461,
-        "narHash": "sha256-aPODl8vAgGQ0ZYFIRisxYG5MOGSkIczvu2Cd8Gb9+1Y=",
+        "lastModified": 1696343447,
+        "narHash": "sha256-B2xAZKLkkeRFG5XcHHSXXcP7To9Xzr59KXeZiRf4vdQ=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "7f53fdb7bdc5bb237da7fefef12d099e4fd611ca",
+        "rev": "c9afaba3dfa4085dbd2ccb38dfade5141e33d9d4",
         "type": "github"
       },
       "original": {
@@ -18,28 +34,45 @@
         "type": "github"
       }
     },
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1659877975,
+        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1695806987,
-        "narHash": "sha256-fX5kGs66NZIxCMcpAGIpxuftajHL8Hil1vjHmjjl118=",
-        "owner": "NixOS",
+        "lastModified": 1696983906,
+        "narHash": "sha256-L7GyeErguS7Pg4h8nK0wGlcUTbfUMDu+HMf1UcyP72k=",
+        "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "f3dab3509afca932f3f4fd0908957709bb1c1f57",
+        "rev": "bd1cde45c77891214131cbbea5b1203e485a9d51",
         "type": "github"
       },
       "original": {
-        "id": "nixpkgs",
-        "type": "indirect"
+        "owner": "nixos",
+        "ref": "nixos-23.05",
+        "repo": "nixpkgs",
+        "type": "github"
       }
     },
     "nixpkgs-lib": {
       "locked": {
         "dir": "lib",
-        "lastModified": 1693471703,
-        "narHash": "sha256-0l03ZBL8P1P6z8MaSDS/MvuU8E75rVxe5eE1N6gxeTo=",
+        "lastModified": 1696019113,
+        "narHash": "sha256-X3+DKYWJm93DRSdC5M6K5hLqzSya9BjibtBsuARoPco=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "3e52e76b70d5508f3cec70b882a29199f4d1ee85",
+        "rev": "f5892ddac112a1e9b3612c39af1b72987ee5783a",
         "type": "github"
       },
       "original": {
@@ -50,10 +83,64 @@
         "type": "github"
       }
     },
+    "nixpkgs-unstable": {
+      "locked": {
+        "lastModified": 1697009197,
+        "narHash": "sha256-viVRhBTFT8fPJTb1N3brQIpFZnttmwo3JVKNuWRVc3s=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "01441e14af5e29c9d27ace398e6dd0b293e25a54",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1689088367,
+        "narHash": "sha256-Y2tl2TlKCWEHrOeM9ivjCLlRAKH3qoPUE/emhZECU14=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "5c9ddb86679c400d6b7360797b8a22167c2053f8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "release-23.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "flake-parts": "flake-parts",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-unstable": "nixpkgs-unstable",
+        "zig-overlay": "zig-overlay"
+      }
+    },
+    "zig-overlay": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs_2"
+      },
+      "locked": {
+        "lastModified": 1697198920,
+        "narHash": "sha256-dtaoksNoOMC3H+FDF3cK+bP+jYvJokYBAFvzCALLDYk=",
+        "owner": "mitchellh",
+        "repo": "zig-overlay",
+        "rev": "2d779a7657e346323ab048b218994dbdc42655d7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "mitchellh",
+        "repo": "zig-overlay",
+        "type": "github"
       }
     }
   },
diff --git a/flake.nix b/flake.nix
index bef0b12..823a8df 100644
--- a/flake.nix
+++ b/flake.nix
@@ -2,8 +2,9 @@
   description = "FabApp";
 
   inputs = {
-    # take unstable if not specified
-    # nixpkgs.url = "github:nixos/nixpkgs/release-23.05";
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-23.05";
+    nixpkgs-unstable.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+    zig-overlay.url = "github:mitchellh/zig-overlay";
     flake-parts.url = "github:hercules-ci/flake-parts";
   };
 
@@ -17,11 +18,18 @@
 
       # https://flake.parts/module-arguments.html#persystem-module-parameters
       perSystem = { pkgs, system, ... }: {
-        _module.args.pkgs = import nixpkgs {
+        # We need unstable for Zig
+        _module.args.pkgs = import inputs.nixpkgs-unstable {
           inherit system;
-          # config.allowUnfree = true;
+          # https://flake.parts/overlays
+          overlays = [
+            inputs.zig-overlay.overlays.default
+          ];
+          config = { };
         };
 
+        formatter = pkgs.nixfmt;
+
         devShells.default = with pkgs;
           mkShell {
             buildInputs = [
@@ -29,20 +37,23 @@
 
               # Zig / webAssembly impl.
               zig
+              # zigpkgs."master" # Issue with X11/GL libraries
               zls
               emscripten
 
-              # Tools
-              nixfmt
-
               # Linux graphical deps
               xorg.libX11
               libGL
+              # xorg.libXcursor
+              # xorg.libXi
+              # xorg.libXext
+              # xorg.libXrandr
+              # xorg.libXinerama
+              # libGLU
             ];
 
           };
 
-        formatter = pkgs.nixfmt;
       };
     };
 }