diff --git a/install.sh b/install.sh
index b07e285..26d0d26 100755
--- a/install.sh
+++ b/install.sh
@@ -24,6 +24,8 @@ main() {
 }
 
 install_everything() {
+	echo "setting up the mac environment"
+	bash mac-files/setup_mac.sh
 
 	echo "updating git modules..."
 	setup_gitmodules
diff --git a/mac-files/setup_mac.sh b/mac-files/setup_mac.sh
old mode 100644
new mode 100755
index 621c1cf..1d6c644
--- a/mac-files/setup_mac.sh
+++ b/mac-files/setup_mac.sh
@@ -1,20 +1,47 @@
+#! /usr/bin/env bash
+[ "$UID" -eq 0 ] || exec sudo bash "$0" "$@"
+set -e
+
 install_homebrew() {
-  ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+  sudo -u $(logname) ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
 }
 
 grab_dependencies() {
-  brew install git
-  brew install vim
-  brew install zsh
-  brew install caskroom/cask/brew-cask
+  sudo -u $(logname) brew install git
+  sudo -u $(logname) brew install vim
+  sudo -u $(logname) brew install zsh
+  sudo -u $(logname) brew install caskroom/cask/brew-cask
+  sudo -u $(logname) brew install tmux
+  sudo -u $(logname) brew cask install hammerspoon
 }
 
 main() {
   # abort if homebrew is already installed; we don't want to accidentaly stomp on things
-  if hash brew 2>/dev/null; then
-    exit(0)
-  install_homebrew
+  if type brew &> /dev/null; then
+    if [[ "$1" != "--force" ]]; then
+      echo "homebrew is already installed; this mac has probably been set up already!"
+      echo "run with --force if you really want to continue"
+      exit 0
+    fi
+  else
+    install_homebrew
+  fi
   grab_dependencies
+  if [ -z $ZSH_NAME ]; then
+    echo "zsh is already the default shell :)"
+  else
+    change_shell_to_zsh
+  fi
+  echo "done setting up the mac!"
 }
 
-main
+change_shell_to_zsh() {
+  if grep -Fqx "$ZSH_PATH" /etc/shells; then
+    echo "zsh already an allowed default shell :)"
+  else
+    echo "$(which zsh)" >> /etc/shells
+  fi
+  chsh -s $(which zsh)
+}
+
+main $@