feat: add Nix flake for ephemeral run and build

Author: tamirelazar

CHANGELOG.md

@@ -26,6 +26,8 @@ Distribution and release-pipeline fixes.
 - One-paste install blocks for Linux and Windows in the README: they fetch the
   latest release binary, install it to a user directory, put it on `PATH`, and
   (on Windows) clear the Mark-of-the-Web so SmartScreen stays quiet.
+- Nix flake: `nix run github:tamirelazar/tslime` runs tslime ephemerally without
+  installing; `nix build` and `nix profile install` are also supported.
 
 ## [0.1.0] - 2026-06-26
 

README.md

@@ -19,6 +19,14 @@ cargo install tslime
 Builds from source (requires Rust 1.70 or later). This is the universal path
 and sidesteps macOS Gatekeeper entirely.
 
+### Try it without installing — Nix
+
+If you have Nix with flakes, run tslime ephemerally — nothing is installed:
+
+```bash
+nix run github:tamirelazar/tslime
+```
+
 ### macOS — Homebrew
 
 ```bash

flake.lock

@@ -0,0 +1,42 @@
+{
+  description = "A lightweight terminal screensaver simulating slime mold growth patterns";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+        # Single source of truth for the version: read it from Cargo.toml so the
+        # flake never drifts from the crate.
+        cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
+      in
+      {
+        packages.default = pkgs.rustPlatform.buildRustPackage {
+          pname = "tslime";
+          version = cargoToml.package.version;
+          src = ./.;
+          cargoLock.lockFile = ./Cargo.lock;
+          # Default (terminal) features only — no C/system dependencies. The gui
+          # and audio features are intentionally not built here.
+          #
+          # Tests are skipped in the Nix sandbox: the visual-regression golden
+          # tests are platform-sensitive (temporal OKLch output differs across
+          # targets) and are gated in CI, which is their source of truth.
+          doCheck = false;
+          meta = {
+            description = "A lightweight terminal screensaver simulating slime mold growth patterns";
+            homepage = "https://github.com/tamirelazar/tslime";
+            license = pkgs.lib.licenses.mit;
+            mainProgram = "tslime";
+          };
+        };
+
+        apps.default = flake-utils.lib.mkApp {
+          drv = self.packages.${system}.default;
+        };
+      });
+}