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 3a5d1af..93f695a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 perf.data
 perf.data.old
 flamegraph.svg
+.direnv
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..3adcc44
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,61 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1783224372,
+        "narHash": "sha256-8i/87eeoqiGE4yOTjwSA3Eh/ziJRQEmd/unYU+K27sk=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "d407951447dcd00442e97087bf374aad70c04cea",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs",
+        "utils": "utils"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "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..4059a9d
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,25 @@
+{
+  inputs = {
+    utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  };
+  outputs = { self, nixpkgs, utils }: utils.lib.eachDefaultSystem (system:
+    let
+      pkgs = nixpkgs.legacyPackages.${system};
+    in
+    {
+      devShell = pkgs.mkShell {
+        buildInputs = with pkgs; [];
+      };
+
+      packages.default = pkgs.rustPlatform.buildRustPackage (finalAttrs: {
+        pname = "dynamic-pangramming";
+        version = "0.1.0";
+
+        src = ./.;
+
+        cargoLock.lockFile = ./Cargo.lock;
+      });
+    }
+  );
+}
diff --git a/src/main.rs b/src/main.rs
index e6eb34f..b33fc6f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -47,6 +47,7 @@ fn solve(dictionary: &mut [(String, LetterSet)], target: LetterSet) -> Option<(u
     let mut path = vec![start];
     let mut done = LetterSet::from(start);
 
+    // this fails sometimes with non-full targets
     while let (_, Some(word)) = bests[done.to_index()] {
         path.push(word);
         done = done.union(LetterSet::from(word));