diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/.gitignore b/.gitignore
index 75be678..d8206ff 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,5 @@
 /*.yuv
 /*.xml
 /*.png
+
+.direnv
diff --git a/cmd/avif/main.go b/cmd/avif/main.go
index e69d6d0..a977c9e 100644
--- a/cmd/avif/main.go
+++ b/cmd/avif/main.go
@@ -8,8 +8,8 @@ import (
 	"io"
 	"os"
 
-	"github.com/Kagami/go-avif"
 	"github.com/docopt/docopt-go"
+	"tulpa.dev/cadey/avif"
 )
 
 const VERSION = "0.0.0"
diff --git a/example_test.go b/example_test.go
index f68b0d2..f0f9f7b 100644
--- a/example_test.go
+++ b/example_test.go
@@ -6,7 +6,7 @@ import (
 	"log"
 	"os"
 
-	"github.com/Kagami/go-avif"
+	"tulpa.dev/cadey/avif"
 )
 
 const usageHelp = "Usage: %s src.jpg dst.avif"
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..4bac686
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1663087123,
+        "narHash": "sha256-cNIRkF/J4mRxDtNYw+9/fBNq/NOA2nCuPOa3EdIyeDs=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9608ace7009ce5bc3aeb940095e01553e635cbc7",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "ref": "nixos-unstable",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs",
+        "utils": "utils"
+      }
+    },
+    "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"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..0cce969
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,40 @@
+{
+  description = "/x/perimental code";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-unstable";
+    utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, utils }@attrs:
+    utils.lib.eachSystem [
+      "x86_64-linux"
+      "aarch64-linux"
+      "x86_64-darwin"
+      "aarch64-darwin"
+    ] (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            (final: prev: {
+              go = prev.go_1_19;
+              buildGoModule = prev.buildGo119Module;
+            })
+          ];
+        };
+
+      in {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            go
+            gopls
+            gotools
+            go-tools
+
+            pkg-config
+            libaom
+          ];
+        };
+      });
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..9ae6a62
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module tulpa.dev/cadey/avif
+
+go 1.19
+
+require github.com/docopt/docopt-go v0.0.0-20180111231733-ee0de3bc6815
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..42c4f03
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/docopt/docopt-go v0.0.0-20180111231733-ee0de3bc6815 h1:bWDMxwH3px2JBh6AyO7hdCn/PkvCZXii8TGj7sbtEbQ=
+github.com/docopt/docopt-go v0.0.0-20180111231733-ee0de3bc6815/go.mod h1:WwZ+bS3ebgob9U8Nd0kOddGdZWjyMGR8Wziv+TBNwSE=
diff --git a/mp4.go b/mp4.go
index d36e299..4227807 100644
--- a/mp4.go
+++ b/mp4.go
@@ -725,7 +725,7 @@ func muxFrame(w io.Writer, m image.Image, subsampling image.YCbCrSubsampleRatio,
 
 	fileData := boxMDAT{data: obuData}
 	fileType := boxFTYP{
-		majorBrand:       itemTypeMIF1,
+		majorBrand:       itemTypeAVIF,
 		compatibleBrands: []fourCC{itemTypeMIF1, itemTypeAVIF, itemTypeMIAF},
 	}
 	metadata := boxMETA{