diff --git a/default.nix b/default.nix
index 388b79d9fa..8285c81524 100644
--- a/default.nix
+++ b/default.nix
@@ -1,16 +1,16 @@
 let sources = import ./nix/sources.nix;
-in { system ? builtins.currentSystem, nixpkgs ? sources.nixpkgs, ... }:
+in { system ? builtins.currentSystem, nixpkgs ? sources.nixpkgs, 
+  multiversal_src ?  if builtins.pathExists ./multiversal/make-multiverse.rb then
+    ./multiversal
+  else
+    sources.multiversal,
+  ... }:
 
 let
   retroPlatforms = import nix/platforms.nix;
 
   lib = ((import nixpkgs) { inherit system; }).lib;
 
-  multiversal_src = if builtins.pathExists ./multiversal/make-multiverse.rb then
-    ./multiversal
-  else
-    sources.multiversal;
-
   # A Nixpkgs overlay.
   overlay = lib.composeManyExtensions [
     ((import nix/overlay.nix) { inherit multiversal_src; })
@@ -30,6 +30,8 @@ let
       crossSystem = plat;
       config = { allowUnsupportedSystem = true; };
     }) retroPlatforms;
+  targetPkgs = lib.mapAttrs (name: cross:
+    cross.buildPackages) crossPkgs;
 
   shell = lib.mapAttrs (name: cross:
     cross.mkShell {
@@ -45,4 +47,5 @@ let
 in shell.m68k // shell // {
   inherit overlay;
   inherit (overlaidPkgs) retro68;
+  targetPkg = targetPkgs;
 }
diff --git a/flake.lock b/flake.lock
index e346e4aee5..9b37985172 100644
--- a/flake.lock
+++ b/flake.lock
@@ -17,6 +17,22 @@
         "type": "indirect"
       }
     },
+    "multiversal": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1682955462,
+        "narHash": "sha256-fOLYuSJOWh/iE7JelpeuT4NgZ/5bZivqV+o9LtiJGxA=",
+        "owner": "autc04",
+        "repo": "multiversal",
+        "rev": "1170bce4c98f1956ad73ca335479d510cd6e8620",
+        "type": "github"
+      },
+      "original": {
+        "owner": "autc04",
+        "repo": "multiversal",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1702312524,
@@ -54,6 +70,7 @@
     "root": {
       "inputs": {
         "flake-parts": "flake-parts",
+        "multiversal": "multiversal",
         "nixpkgs": "nixpkgs"
       }
     }
diff --git a/flake.nix b/flake.nix
index 929e34f4ff..5d64f032ef 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,31 +3,58 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    multiversal.url = "github:autc04/multiversal";
+    multiversal.flake = false;
   };
 
-  outputs = inputs@{ flake-parts, ... }:
-    flake-parts.lib.mkFlake { inherit inputs; } {
-      imports = [
-        # To import a flake module
-        # 1. Add foo to inputs
-        # 2. Add foo as a parameter to the outputs function
-        # 3. Add here: foo.flakeModule
+  outputs = inputs@{ flake-parts, nixpkgs, multiversal, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } ({ self, lib, retroPlatforms, ... }: {
+      _module.args.lib = import (nixpkgs + "/lib");
+      _module.args.retroPlatforms = import ./nix/platforms.nix;
 
-      ];
       systems = [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin" ];
-      perSystem = { config, self', inputs', pkgs, system, ... }: {
-        # Per-system attributes can be defined here. The self' and inputs'
-        # module parameters provide easy access to attributes of the same
-        # system.
+      perSystem = { config, self', inputs', pkgs, system, ... }:
+        {
+          _module.args.pkgs = import nixpkgs { inherit system; overlays = [ self.overlays.default ]; };
 
-        # Equivalent to  inputs'.nixpkgs.legacyPackages.hello;
-        packages.default = pkgs.hello;
-      };
+          legacyPackages.crossPkgs = lib.mapAttrs
+            (name: plat:
+              import nixpkgs {
+                inherit system;
+                overlays = [ self.overlays.default ];
+                crossSystem = plat;
+                config = { allowUnsupportedSystem = true; };
+              })
+            retroPlatforms;
+
+          devShells = {
+            default = pkgs.mkShell {
+              inputsFrom = [ pkgs.retro68.monolithic ];
+              nativeBuildInputs = [ pkgs.nixpkgs-fmt ];
+            };
+          } // lib.mapAttrs
+            (name: cross:
+              cross.mkShell
+                {
+                  nativeBuildInputs = with pkgs; [
+                    retro68.hfsutils
+                    retro68.tools
+                    cmake
+                    gnumake
+                  ];
+                  buildInputs = [ cross.retro68.console ];
+                } // cross)
+            self'.legacyPackages.crossPkgs;
+
+
+        };
       flake = {
-        # The usual flake attributes can be defined here, including system-
-        # agnostic ones like nixosModule and system-enumerating ones, although
-        # those are more easily expressed in perSystem.
-
+        overlays.default =
+          lib.composeManyExtensions [
+            ((import nix/overlay.nix) { multiversal_src = multiversal; })
+            (import nix/universal.nix)
+            (import nix/samples.nix)
+          ];
       };
-    };
+    });
 }
diff --git a/nix/sources.json b/nix/sources.json
index f017eed65e..15b7018841 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -5,10 +5,10 @@
         "homepage": null,
         "owner": "autc04",
         "repo": "multiversal",
-        "rev": "ce33b1bada9b0acb14021c21ac916927c757d525",
-        "sha256": "1fsyjad4kwsqgr2mlx9dfl7z8z42cf2sgw1arqmci47zhaj8is1f",
+        "rev": "1170bce4c98f1956ad73ca335479d510cd6e8620",
+        "sha256": "040vi7c2wggaazm2nrjvzrkn10sgmsbrcpmj2gi1ynjf4awxiqkw",
         "type": "tarball",
-        "url": "https://github.com/autc04/multiversal/archive/ce33b1bada9b0acb14021c21ac916927c757d525.tar.gz",
+        "url": "https://github.com/autc04/multiversal/archive/1170bce4c98f1956ad73ca335479d510cd6e8620.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "niv": {
@@ -17,10 +17,10 @@
         "homepage": "https://github.com/nmattia/niv",
         "owner": "nmattia",
         "repo": "niv",
-        "rev": "5830a4dd348d77e39a0f3c4c762ff2663b602d4c",
-        "sha256": "1d3lsrqvci4qz2hwjrcnd8h5vfkg8aypq3sjd4g3izbc8frwz5sm",
+        "rev": "6bd7cd686220bf3db0e212481faf9578e8c8ff0f",
+        "sha256": "15claxlj6y15db67qc7kb4vzyn6sv7r13z4q502vq7a4z2488z94",
         "type": "tarball",
-        "url": "https://github.com/nmattia/niv/archive/5830a4dd348d77e39a0f3c4c762ff2663b602d4c.tar.gz",
+        "url": "https://github.com/nmattia/niv/archive/6bd7cd686220bf3db0e212481faf9578e8c8ff0f.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs": {
@@ -29,10 +29,10 @@
         "homepage": "",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "d1e59cfc49961e121583abe32e2f3db1550fbcff",
-        "sha256": "03ldf1dlxqf3g8qh9x5vp6vd9zvvr481fyjds111imll69y60wpm",
+        "rev": "2766f77c32e171a04d59b636a91083bae862274e",
+        "sha256": "1xk1f62n00z7q5i3pf4c8c4rlv5k4jwpgh0pqgzw1l40vhdkixk9",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/d1e59cfc49961e121583abe32e2f3db1550fbcff.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/2766f77c32e171a04d59b636a91083bae862274e.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }
diff --git a/nix/sources.nix b/nix/sources.nix
index 1938409ddd..fe3dadf7eb 100644
--- a/nix/sources.nix
+++ b/nix/sources.nix
@@ -10,29 +10,50 @@ let
     let
       name' = sanitizeName name + "-src";
     in
-      if spec.builtin or true then
-        builtins_fetchurl { inherit (spec) url sha256; name = name'; }
-      else
-        pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
+    if spec.builtin or true then
+      builtins_fetchurl { inherit (spec) url sha256; name = name'; }
+    else
+      pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
 
   fetch_tarball = pkgs: name: spec:
     let
       name' = sanitizeName name + "-src";
     in
-      if spec.builtin or true then
-        builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
-      else
-        pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
+    if spec.builtin or true then
+      builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
+    else
+      pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
 
   fetch_git = name: spec:
     let
       ref =
-        if spec ? ref then spec.ref else
+        spec.ref or (
           if spec ? branch then "refs/heads/${spec.branch}" else
-            if spec ? tag then "refs/tags/${spec.tag}" else
-              abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
+          if spec ? tag then "refs/tags/${spec.tag}" else
+          abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!"
+        );
+      submodules = spec.submodules or false;
+      submoduleArg =
+        let
+          nixSupportsSubmodules = builtins.compareVersions builtins.nixVersion "2.4" >= 0;
+          emptyArgWithWarning =
+            if submodules
+            then
+              builtins.trace
+                (
+                  "The niv input \"${name}\" uses submodules "
+                  + "but your nix's (${builtins.nixVersion}) builtins.fetchGit "
+                  + "does not support them"
+                )
+                { }
+            else { };
+        in
+        if nixSupportsSubmodules
+        then { inherit submodules; }
+        else emptyArgWithWarning;
     in
-      builtins.fetchGit { url = spec.repo; inherit (spec) rev; inherit ref; };
+    builtins.fetchGit
+      ({ url = spec.repo; inherit (spec) rev; inherit ref; } // submoduleArg);
 
   fetch_local = spec: spec.path;
 
@@ -66,16 +87,16 @@ let
       hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
       hasThisAsNixpkgsPath = <nixpkgs> == ./.;
     in
-      if builtins.hasAttr "nixpkgs" sources
-      then sourcesNixpkgs
-      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
-        import <nixpkgs> {}
-      else
-        abort
-          ''
-            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
-            add a package called "nixpkgs" to your sources.json.
-          '';
+    if builtins.hasAttr "nixpkgs" sources
+    then sourcesNixpkgs
+    else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
+      import <nixpkgs> { }
+    else
+      abort
+        ''
+          Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+          add a package called "nixpkgs" to your sources.json.
+        '';
 
   # The actual fetching function.
   fetch = pkgs: name: spec:
@@ -95,13 +116,13 @@ let
   # the path directly as opposed to the fetched source.
   replace = name: drv:
     let
-      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
+      saneName = stringAsChars (c: if (builtins.match "[a-zA-Z0-9]" c) == null then "_" else c) name;
       ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
     in
-      if ersatz == "" then drv else
-        # this turns the string into an actual Nix path (for both absolute and
-        # relative paths)
-        if builtins.substring 0 1 ersatz == "/" then /. + ersatz else /. + builtins.getEnv "PWD" + "/${ersatz}";
+    if ersatz == "" then drv else
+      # this turns the string into an actual Nix path (for both absolute and
+      # relative paths)
+    if builtins.substring 0 1 ersatz == "/" then /. + ersatz else /. + builtins.getEnv "PWD" + "/${ersatz}";
 
   # Ports of functions for older nix versions
 
@@ -112,7 +133,7 @@ let
   );
 
   # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
-  range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
+  range = first: last: if first > last then [ ] else builtins.genList (n: first + n) (last - first + 1);
 
   # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
   stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
@@ -123,43 +144,46 @@ let
   concatStrings = builtins.concatStringsSep "";
 
   # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
-  optionalAttrs = cond: as: if cond then as else {};
+  optionalAttrs = cond: as: if cond then as else { };
 
   # fetchTarball version that is compatible between all the versions of Nix
   builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
     let
       inherit (builtins) lessThan nixVersion fetchTarball;
     in
-      if lessThan nixVersion "1.12" then
-        fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
-      else
-        fetchTarball attrs;
+    if lessThan nixVersion "1.12" then
+      fetchTarball ({ inherit url; } // (optionalAttrs (name != null) { inherit name; }))
+    else
+      fetchTarball attrs;
 
   # fetchurl version that is compatible between all the versions of Nix
   builtins_fetchurl = { url, name ? null, sha256 }@attrs:
     let
       inherit (builtins) lessThan nixVersion fetchurl;
     in
-      if lessThan nixVersion "1.12" then
-        fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
-      else
-        fetchurl attrs;
+    if lessThan nixVersion "1.12" then
+      fetchurl ({ inherit url; } // (optionalAttrs (name != null) { inherit name; }))
+    else
+      fetchurl attrs;
 
   # Create the final "sources" from the config
   mkSources = config:
-    mapAttrs (
-      name: spec:
-        if builtins.hasAttr "outPath" spec
-        then abort
-          "The values in sources.json should not have an 'outPath' attribute"
-        else
-          spec // { outPath = replace name (fetch config.pkgs name spec); }
-    ) config.sources;
+    mapAttrs
+      (
+        name: spec:
+          if builtins.hasAttr "outPath" spec
+          then
+            abort
+              "The values in sources.json should not have an 'outPath' attribute"
+          else
+            spec // { outPath = replace name (fetch config.pkgs name spec); }
+      )
+      config.sources;
 
   # The "config" used by the fetchers
   mkConfig =
     { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
-    , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
+    , sources ? if sourcesFile == null then { } else builtins.fromJSON (builtins.readFile sourcesFile)
     , system ? builtins.currentSystem
     , pkgs ? mkPkgs sources system
     }: rec {
@@ -171,4 +195,4 @@ let
     };
 
 in
-mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }
+mkSources (mkConfig { }) // { __functor = _: settings: mkSources (mkConfig settings); }