diff --git a/.envrc b/.envrc
index daafe18d9a..1d953f4bd7 100644
--- a/.envrc
+++ b/.envrc
@@ -1,154 +1 @@
-# Load environment variables from `nix-shell` and export it out.
-#
-# Usage: use_nix [-s <nix-expression>] [-w <path>] [-w <path>] ...
-#   -s nix-expression: The nix expression to use for building the shell environment.
-#   -w path: watch a file for changes. It can be specified multiple times. The
-#      shell specified with -s is automatically watched.
-#
-#   If no nix-expression were given with -s, it will attempt to find and load
-#   the shell using the following files in order: shell.nix and default.nix.
-#
-# Example:
-#   -  use_nix
-#   -  use_nix -s shell.nix -w .nixpkgs-version.json
-#
-# The dependencies pulled by nix-shell are added to Nix's garbage collector
-# roots, such that the environment remains persistent.
-#
-# Nix-shell is invoked only once per environment, and the output is cached for
-# better performance. If any of the watched files change, then the environment
-# is rebuilt.
-#
-# To remove old environments, and allow the GC to collect their dependencies:
-# rm -f .direnv
-#
-use_nix() {
-	if ! validate_version; then
-		echo "This .envrc requires direnv version 2.18.2 or above."
-		exit 1
-	fi
-
-	# define all local variables
-	local shell
-	local files_to_watch=()
-
-	local opt OPTARG OPTIND # define vars used by getopts locally
-	while getopts ":n:s:w:" opt; do
-		case "${opt}" in
-			s)
-				shell="${OPTARG}"
-				files_to_watch=("${files_to_watch[@]}" "${shell}")
-				;;
-			w)
-				files_to_watch=("${files_to_watch[@]}" "${OPTARG}")
-				;;
-			:)
-				fail "Invalid option: $OPTARG requires an argument"
-				;;
-			\?)
-				fail "Invalid option: $OPTARG"
-				;;
-		esac
-	done
-	shift $((OPTIND -1))
-
-	if [[ -z "${shell}" ]]; then
-		if [[ -f shell.nix ]]; then
-			shell=shell.nix
-			files_to_watch=("${files_to_watch[@]}" shell.nix)
-		elif [[ -f default.nix ]]; then
-			shell=default.nix
-			files_to_watch=("${files_to_watch[@]}" default.nix)
-		else
-			fail "ERR: no shell was given"
-		fi
-	fi
-
-	local f
-	for f in "${files_to_watch[@]}"; do
-		if ! [[ -f "${f}" ]]; then
-			fail "cannot watch file ${f} because it does not exist"
-		fi
-	done
-
-	# compute the hash of all the files that makes up the development environment
-	local env_hash="$(hash_contents "${files_to_watch[@]}")"
-
-	# define the paths
-	local dir="$(direnv_layout_dir)"
-	local wd="${dir}/wd-${env_hash}"
-	local drv="${wd}/env.drv"
-	local dump="${wd}/dump.env"
-
-	# Generate the environment if we do not have one generated already.
-	if [[ ! -f "${drv}" ]]; then
-		mkdir -p "${wd}"
-
-		log_status "use nix: deriving new environment"
-		IN_NIX_SHELL=1 nix-instantiate --add-root "${drv}" --indirect "${shell}" > /dev/null
-		nix-store -r $(nix-store --query --references "${drv}") --add-root "${wd}/dep" --indirect > /dev/null
-		if [[ "${?}" -ne 0 ]] || [[ ! -f "${drv}" ]]; then
-			rm -rf "${wd}"
-			fail "use nix: was not able to derive the new environment. Please run 'direnv reload' to try again."
-		fi
-
-		log_status "use nix: updating cache"
-		nix-shell "${drv}" --show-trace --run "$(join_args "$direnv" dump bash)" > "${dump}"
-		if [[ "${?}" -ne 0 ]] || [[ ! -f "${dump}" ]] || ! grep -q IN_NIX_SHELL "${dump}"; then
-			rm -rf "${wd}"
-			fail "use nix: was not able to update the cache of the environment. Please run 'direnv reload' to try again."
-		fi
-	fi
-
-	# evaluate the dump created by nix-shell earlier, but have to merge the PATH
-	# with the current PATH
-	# NOTE: we eval the dump here as opposed to direnv_load it because we don't
-	# want to persist environment variables coming from the shell at the time of
-	# the dump. See https://github.com/direnv/direnv/issues/405 for context.
-	local path_backup="${PATH}"
-	eval $(cat "${dump}")
-	export PATH="${PATH}:${path_backup}"
-
-	# cleanup the environment of variables that are not requried, or are causing issues.
-	unset shellHook  # when shellHook is present, then any nix-shell'd script will execute it!
-
-	# watch all the files we were asked to watch for the environment
-	for f in "${files_to_watch[@]}"; do
-		watch_file "${f}"
-	done
-}
-
-fail() {
-	log_error "${@}"
-	exit 1
-}
-
-hash_contents() {
-	if has md5sum; then
-		cat "${@}" | md5sum | cut -c -32
-	elif has md5; then
-		cat "${@}" | md5 -q
-	fi
-}
-
-hash_file() {
-	if has md5sum; then
-		md5sum "${@}" | cut -c -32
-	elif has md5; then
-		md5 -q "${@}"
-	fi
-}
-
-validate_version() {
-	local version="$("${direnv}" version)"
-	local major="$(echo "${version}" | cut -d. -f1)"
-	local minor="$(echo "${version}" | cut -d. -f2)"
-	local patch="$(echo "${version}" | cut -d. -f3)"
-
-	if [[ "${major}" -gt 2 ]]; then return 0; fi
-	if [[ "${major}" -eq 2 ]] && [[ "${minor}" -gt 18 ]]; then return 0; fi
-	if [[ "${major}" -eq 2 ]] && [[ "${minor}" -eq 18 ]] && [[ "${patch}" -ge 2 ]]; then return 0; fi
-	return 1
-}
-
-use_nix -s shell.nix
+use nix
diff --git a/compiler/build/src/link.rs b/compiler/build/src/link.rs
index 95983e1a8d..c535f86e57 100644
--- a/compiler/build/src/link.rs
+++ b/compiler/build/src/link.rs
@@ -466,8 +466,8 @@ fn link_macos(
                 "-lc++",
                 // "-lc++abi",
                 // "-lunwind", // TODO will eventually need this, see https://github.com/rtfeldman/roc/pull/554#discussion_r496370840
-                "-framework",
-                "Security", // This "-framework Security" arg is needed for the `rand` crate in examples/cli
+                // "-framework", // Uncomment this line & the following ro run the `rand` crate in examples/cli
+                // "Security",
                 // Output
                 "-o",
                 output_path.to_str().unwrap(), // app
diff --git a/nix/zig.nix b/nix/zig.nix
index 6f5f49bd18..ae8708625d 100644
--- a/nix/zig.nix
+++ b/nix/zig.nix
@@ -1,37 +1,37 @@
-{ pkgs, isMacOS, isAarch64 }:
+{ pkgs, isDarwin, isAarch64 }:
 
-if isMacOS then
+if isDarwin then
   let
     version = "0.7.1";
     osName =
-      if isMacOS
-        then "macos"
-        else "linux";
+      if isDarwin
+      then "macos"
+      else "linux";
     archName =
       if isAarch64
-        then "aarch64"
-        else "x86_64";
+      then "aarch64"
+      else "x86_64";
     archiveName = "zig-${osName}-${archName}-${version}";
     sha256 = "845cb17562978af0cf67e3993f4e33330525eaf01ead9386df9105111e3bc519";
   in
-  pkgs.stdenv.mkDerivation {
-    pname = "zig";
-    version = version;
-    buildInputs = [ pkgs.gzip ];
-    src = pkgs.fetchurl {
-      inherit sha256;
-      name = "${archiveName}.tar.xz";
-      url = "https://ziglang.org/download/${version}/${archiveName}.tar.xz";
-    };
-    phases = [ "installPhase" ];
-    installPhase = ''
-      mkdir -p $out/bin
-      tar -xf $src
-      cp ${archiveName}/zig $out/zig
-      cp -r ${archiveName}/lib $out/lib
-      ln -s "$out/zig" "$out/bin/zig"
-      chmod +x $out/bin/zig
-    '';
-  }
+    pkgs.stdenv.mkDerivation {
+      pname = "zig";
+      version = version;
+      buildInputs = [ pkgs.gzip ];
+      src = pkgs.fetchurl {
+        inherit sha256;
+        name = "${archiveName}.tar.xz";
+        url = "https://ziglang.org/download/${version}/${archiveName}.tar.xz";
+      };
+      phases = [ "unpackPhase" ];
+      unpackPhase = ''
+        mkdir -p $out/bin
+        tar -xf $src
+        cp ${archiveName}/zig $out/zig
+        cp -r ${archiveName}/lib $out/lib
+        ln -s "$out/zig" "$out/bin/zig"
+        chmod +x $out/bin/zig
+      '';
+    }
 else
   pkgs.zig
diff --git a/nix/zls.nix b/nix/zls.nix
deleted file mode 100644
index 29f0feb033..0000000000
--- a/nix/zls.nix
+++ /dev/null
@@ -1,28 +0,0 @@
-{ pkgs, zig }:
-
-# As of 2020-10-25, building zls is not available on Nix. For some reason,
-# this hangs on `zig build`. I'll try to figure it our later.
-
-let
-  rev = "e8c20351d85da8eb4bf22480045b994007284d69";
-in
-pkgs.stdenv.mkDerivation {
-  pname = "zig-language-server";
-  version = rev;
-  src = pkgs.fetchgit {
-    inherit rev;
-    fetchSubmodules = true;
-    url = "https://github.com/zigtools/zls.git";
-    sha256 = "06g8gml1g0fmvcfysy93bd1hb64vjd2v12x3kgxz58kmk5z0168y";
-  };
-  phases = [ "buildPhase" "installPhase" ];
-  buildInputs = [ zig ];
-  buildPhase = ''
-    zig build
-  '';
-  installPhase = ''
-    mkdir -p $out/bin
-    cp ./zig-cache/bin/zls $out/bin/zls
-    chmod +x $out/bin/zls
-  '';
-}
diff --git a/shell.nix b/shell.nix
index 7b7d61fd55..ddb786a8b3 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,116 +1,113 @@
 {}:
 
 let
-  splitSystem = builtins.split "-" builtins.currentSystem;
-  currentArch = builtins.elemAt splitSystem 0;
-  currentOS = builtins.elemAt splitSystem 2;
-in
-  with {
-    # Look here for information about how pin version of nixpkgs
-    #  → https://nixos.wiki/wiki/FAQ/Pinning_Nixpkgs
-    pkgs = import (
-      builtins.fetchGit {
-        # name = "nixpkgs-2021-04-23";
-        url = "https://github.com/nixos/nixpkgs/";
-        ref = "refs/heads/nixpkgs-unstable";
-        rev = "8d0340aee5caac3807c58ad7fa4ebdbbdd9134d6";
-      }
-    ) {};
+  # Look here for information about how pin version of nixpkgs
+  #  → https://nixos.wiki/wiki/FAQ/Pinning_Nixpkgs
+  # TODO: We should probably use flakes at somepoint
+  pkgs = import (
+    builtins.fetchGit {
+      # name = "nixpkgs-2021-04-23";
+      url = "https://github.com/nixos/nixpkgs/";
+      ref = "refs/heads/nixpkgs-unstable";
+      rev = "8d0340aee5caac3807c58ad7fa4ebdbbdd9134d6";
+    }
+  ) {};
 
-    isMacOS = currentOS == "darwin";
-    isLinux = currentOS == "linux";
-    isAarch64 = currentArch == "aarch64";
-  };
+  currentArch = builtins.elemAt (builtins.split "-" builtins.currentSystem) 0;
+  isAarch64 = currentArch == "aarch64";
 
-  with (pkgs);
+  darwinInputs =
+    with pkgs;
+    lib.optionals stdenv.isDarwin (
+      with pkgs.darwin.apple_sdk.frameworks; [
+        AppKit
+        CoreFoundation
+        CoreServices
+        CoreVideo
+        Foundation
+        Metal
+        Security
+      ]
+    );
 
-  let
-    darwin-inputs =
-      if isMacOS then
-        with pkgs.darwin.apple_sdk.frameworks; [
-          AppKit
-          CoreFoundation
-          CoreServices
-          CoreVideo
-          Foundation
-          Metal
-          Security
-        ]
-      else
-        [];
-
-    linux-inputs =
-      if isLinux then
-        [
-          valgrind
-          vulkan-headers
-          vulkan-loader
-          vulkan-tools
-          vulkan-validation-layers
-          xorg.libX11
-          xorg.libXcursor
-          xorg.libXrandr
-          xorg.libXi
-          xorg.libxcb
-        ]
-      else
-        [];
-
-    llvmPkgs = pkgs.llvmPackages_10;
-    zig = import ./nix/zig.nix { inherit pkgs isMacOS isAarch64; };
-    inputs = [
-      # build libraries
-      rustc
-      cargo
-      clippy
-      rustfmt
-      cmake
-      git
-      python3
-      llvmPkgs.llvm
-      llvmPkgs.clang
-      pkg-config
-      zig
-      # lib deps
-      llvmPkgs.libcxx
-      llvmPkgs.libcxxabi
-      libffi
-      libunwind
-      libxml2
-      ncurses
-      zlib
-      libiconv
-      # faster builds - see https://github.com/rtfeldman/roc/blob/trunk/BUILDING_FROM_SOURCE.md#use-lld-for-the-linker
-      llvmPkgs.lld
-      # dev tools
-      # rust-analyzer
-      # (import ./nix/zls.nix { inherit pkgs zig; })
+  linuxInputs =
+    with pkgs;
+    lib.optionals stdenv.isLinux [
+      valgrind
+      vulkan-headers
+      vulkan-loader
+      vulkan-tools
+      vulkan-validation-layers
+      xorg.libX11
+      xorg.libXcursor
+      xorg.libXrandr
+      xorg.libXi
+      xorg.libxcb
     ];
 
-  in
-    mkShell (
-      {
-        buildInputs = inputs ++ darwin-inputs ++ linux-inputs;
+  llvmPkgs = pkgs.llvmPackages_10;
 
-        # Additional Env vars
-        LLVM_SYS_100_PREFIX = "${llvmPkgs.llvm}";
-        LD_LIBRARY_PATH = stdenv.lib.makeLibraryPath
-          (
-            [
-              pkg-config
-              stdenv.cc.cc.lib
-              llvmPkgs.libcxx
-              llvmPkgs.libcxxabi
-              libunwind
-              libffi
-              ncurses
-              zlib
-            ] ++ linux-inputs
-          );
+  zig = import ./nix/zig.nix {
+    pkgs = pkgs;
+    isDarwin = pkgs.stdenv.isDarwin;
+    isAarch64 = isAarch64;
+  };
 
-        # Aliases don't work cross shell, so we do this
-        shellHook = ''
-          export PATH="$PATH:$PWD/nix/bin"
-        '';
-      }
-    )
+  inputs = with pkgs;[
+    # build libraries
+    rustc
+    cargo
+    clippy
+    rustfmt
+    cmake
+    git
+    python3
+    llvmPkgs.llvm
+    llvmPkgs.clang
+    pkg-config
+    zig
+
+    # lib deps
+    llvmPkgs.libcxx
+    llvmPkgs.libcxxabi
+    libffi
+    libunwind
+    libxml2
+    ncurses
+    zlib
+    libiconv
+
+    # faster builds - see https://github.com/rtfeldman/roc/blob/trunk/BUILDING_FROM_SOURCE.md#use-lld-for-the-linker
+    llvmPkgs.lld
+  ];
+in
+pkgs.mkShell
+  {
+    buildInputs = inputs ++ darwinInputs ++ linuxInputs;
+
+    # Additional Env vars
+    LLVM_SYS_100_PREFIX = "${llvmPkgs.llvm}";
+    LD_LIBRARY_PATH =
+      with pkgs;
+      lib.makeLibraryPath
+        (
+          [
+            pkg-config
+            stdenv.cc.cc.lib
+            llvmPkgs.libcxx
+            llvmPkgs.libcxxabi
+            libunwind
+            libffi
+            ncurses
+            zlib
+          ]
+          ++ linuxInputs
+        );
+
+    # Non Nix llvm installs names the bin llvm-as-${version}, so we
+    # alias `llvm` to `llvm-as-${version}` here.
+    # This the name of the file in nix/bin will need to be updated whenever llvm is updated
+    shellHook = ''
+      export PATH="$PATH:$PWD/nix/bin"
+    '';
+  }