diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3e4f61f..666d9e2 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,24 +8,10 @@ jobs:
   elm-test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-
-      - uses: actions/setup-node@v1
-        with:
-          node-version: "12"
-
-      - uses: actions/cache@v2
+      - uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v22
         with:
-          path: |
-            ~/.npm
-            ~/.elm
-            elm-stuff
-          key: ${{ runner.os }}-cache
-
-      - run: npm install -g elm@latest-0.19.1 elm-test@0.19.1-revision6 elm-review@2.5.0 elm-format@0.8.5
-
-      - run: elm-format --validate .
-
-      - run: elm-review
-
-      - run: elm-test
+          github_access_token: ${{ secrets.GITHUB_TOKEN }}
+      - run: nix develop --command elm-format --validate .
+      - run: nix develop --command elm-review
+      - run: nix develop --command elm-test
diff --git a/elm.json b/elm.json
index 9840802..4355d20 100644
--- a/elm.json
+++ b/elm.json
@@ -21,6 +21,6 @@
         "ianmackenzie/elm-units": "2.7.0 <= v < 3.0.0"
     },
     "test-dependencies": {
-        "elm-explorations/test": "1.2.2 <= v < 2.0.0"
+        "elm-explorations/test": "2.2.0 <= v < 3.0.0"
     }
 }
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..2921cfd
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,61 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1710146030,
+        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1711124224,
+        "narHash": "sha256-l0zlN/3CiodvWDtfBOVxeTwYSRz93muVbXWSpaMjXxM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "56528ee42526794d413d6f244648aaee4a7b56c0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-23.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..d64ddda
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,22 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let pkgs = nixpkgs.legacyPackages.${system};
+      in
+      {
+        devShells.default = with pkgs; with elmPackages; mkShell {
+          buildInputs = [
+            elm
+            elm-format
+            elm-test
+            elm-review
+            elm-json
+          ];
+        };
+      });
+}
diff --git a/review/elm.json b/review/elm.json
index 1b7c4e8..7cb6cf3 100644
--- a/review/elm.json
+++ b/review/elm.json
@@ -9,11 +9,11 @@
             "elm/core": "1.0.5",
             "elm/json": "1.1.3",
             "elm/project-metadata-utils": "1.0.1",
-            "jfmengels/elm-review": "2.4.1",
-            "jfmengels/elm-review-simplify": "1.0.1",
-            "jfmengels/elm-review-unused": "1.1.9",
-            "jfmengels/elm-review-performance": "1.0.0",
-            "stil4m/elm-syntax": "7.2.2"
+            "jfmengels/elm-review": "2.13.1",
+            "jfmengels/elm-review-simplify": "2.1.3",
+            "jfmengels/elm-review-unused": "1.2.0",
+            "jfmengels/elm-review-performance": "1.0.2",
+            "stil4m/elm-syntax": "7.3.2"
         },
         "indirect": {
             "elm/html": "1.0.0",
@@ -21,15 +21,15 @@
             "elm/random": "1.0.0",
             "elm/time": "1.0.0",
             "elm/virtual-dom": "1.0.2",
-            "elm-community/list-extra": "8.3.0",
-            "elm-explorations/test": "1.2.2",
+            "elm-community/list-extra": "8.7.0",
+            "elm-explorations/test": "2.2.0",
             "rtfeldman/elm-hex": "1.0.0",
             "stil4m/structured-writer": "1.0.3"
         }
     },
     "test-dependencies": {
         "direct": {
-            "elm-explorations/test": "1.2.2"
+            "elm-explorations/test": "2.2.0"
         },
         "indirect": {}
     }
diff --git a/review/src/ReviewConfig.elm b/review/src/ReviewConfig.elm
index 5630c29..2363de5 100644
--- a/review/src/ReviewConfig.elm
+++ b/review/src/ReviewConfig.elm
@@ -34,6 +34,6 @@ config =
     , NoUnused.Parameters.rule
     , NoUnused.Patterns.rule
     , NoUnused.Variables.rule
-    , Simplify.rule
+    , Simplify.rule Simplify.defaults
     , NoUnoptimizedRecursion.rule (NoUnoptimizedRecursion.optOutWithComment "IGNORE TCO")
     ]
diff --git a/scripts/elm-publish.sh b/scripts/elm-publish.sh
index ab7d1a6..c387a8e 100755
--- a/scripts/elm-publish.sh
+++ b/scripts/elm-publish.sh
@@ -26,7 +26,7 @@ git commit -m "Bump to $version"
 git push
 last_commit=$(git rev-parse HEAD)
 
-git rm -rf --ignore-unmatch .github benchmarks examples scripts tests elm-physics.gif
+git rm -rf --ignore-unmatch .github benchmarks examples scripts tests elm-physics.gif flake.nix
 sed -i.bak "s+https://unsoundscapes.com/elm-physics/+https://unsoundscapes.com/elm-physics/$version/+g" README.md
 sed -i.bak "s+https://github.com/w0rm/elm-physics/tree/main/+https://github.com/w0rm/elm-physics/tree/$last_commit/+g" README.md
 rm README.md.bak
diff --git a/src/Shapes/Convex.elm b/src/Shapes/Convex.elm
index 9dafad7..32b792e 100644
--- a/src/Shapes/Convex.elm
+++ b/src/Shapes/Convex.elm
@@ -280,9 +280,11 @@ initFacesHelp visited vertices faceByEdgeIndex facesToCheck edgesToCheck current
         newEdgesToCheck =
             List.foldl
                 (\{ indices } res ->
-                    case indices of
-                        ( i1, i2, i3 ) ->
-                            ( i2, i1 ) :: ( i3, i2 ) :: ( i1, i3 ) :: res
+                    let
+                        ( i1, i2, i3 ) =
+                            indices
+                    in
+                    ( i2, i1 ) :: ( i3, i2 ) :: ( i1, i3 ) :: res
                 )
                 []
                 coplanar
diff --git a/tests/Shapes/ConvexTest.elm b/tests/Shapes/ConvexTest.elm
index c85d9bc..255782a 100644
--- a/tests/Shapes/ConvexTest.elm
+++ b/tests/Shapes/ConvexTest.elm
@@ -8,7 +8,6 @@ module Shapes.ConvexTest exposing
     , volume
     )
 
-import Block3d exposing (vertices)
 import Expect
 import Extra.Expect as Expect
 import Fixtures.Convex
@@ -102,8 +101,7 @@ faces =
                 (List.map
                     (\{ normal, vertices } ->
                         \_ ->
-                            Expect.true
-                                "normal points inside"
+                            Expect.equal True
                                 (List.all
                                     (\v ->
                                         let